1.
Josephson junction
–
The Josephson effect is the phenomenon of supercurrent—i. e. A current that flows indefinitely long without any voltage applied—across a device known as a Josephson junction, the weak link can consist of a thin insulating barrier, a short section of non-superconducting metal, or a physical constriction that weakens the superconductivity at the point of contact. The Josephson effect is an example of a quantum phenomenon. It is named after the British physicist Brian David Josephson, who predicted in 1962 the mathematical relationships for the current, the first paper to claim the discovery of Josephsons effect, and to make the requisite experimental checks, was that of Philip Anderson and John Rowell. These authors were awarded patents on the effects that were never enforced, before Josephsons prediction, it was only known that normal electrons can flow through an insulating barrier, by means of quantum tunneling. Josephson was the first to predict the tunneling of superconducting Cooper pairs, for this work, Josephson received the Nobel Prize in Physics in 1973. Josephson junctions have important applications in quantum-mechanical circuits, such as SQUIDs, superconducting qubits, the NIST standard for one volt is achieved by an array of 20,208 Josephson junctions in series. Types of Josephson junction include the pi Josephson junction, varphi Josephson junction, long Josephson junction, a Dayem bridge is a thin-film variant of the Josephson junction in which the weak link consists of a superconducting wire with dimensions on the scale of a few micrometres or less. The Josephson junction count of a device is used as a benchmark for its complexity and they are widely used in science and engineering. In precision metrology, the Josephson effect provides an exactly reproducible conversion between frequency and voltage, however, BIPM has not changed the official SI unit definition. Single-electron transistors are often constructed of superconducting materials, allowing use to be made of the Josephson effect to achieve novel effects, the resulting device is called a superconducting single-electron transistor. The Josephson effect is used for the most precise measurements of elementary charge in terms of the Josephson constant. RSFQ digital electronics is based on shunted Josephson junctions, Josephson junctions are integral in superconducting quantum computing as qubits such as in a flux qubit or others schemes where the phase and charge act as the conjugate variables. Superconducting tunnel junction detectors may become a replacement for CCDs for use in astronomy. These devices are effective across a spectrum from ultraviolet to infrared. The technology has been tried out on the William Herschel Telescope in the SCAM instrument, quiterons and similar superconducting switching devices. Josephson effect has also observed in SHeQUIDs, the superfluid helium analog of a dc-SQUID. The critical current is an important phenomenological parameter of the device that can be affected by temperature as well as by a magnetic field
Josephson junction
–
Josephson junction array chip developed by the
National Bureau of Standards as a standard volt
Josephson junction
–
Typical I-V characteristic of a
superconducting tunnel junction, a common kind of Josephson junction. The scale of the vertical axis is 50 μA and that of the horizontal one is 1 mV. The bar at represents the DC Josephson effect, while the current at large values of is due to the finite value of the superconductor bandgap and not reproduced by the above equations.
2.
NIST
–
The National Institute of Standards and Technology is a measurement standards laboratory, and a non-regulatory agency of the United States Department of Commerce. Its mission is to promote innovation and industrial competitiveness, in 1821, John Quincy Adams had declared Weights and measures may be ranked among the necessities of life to every individual of human society. From 1830 until 1901, the role of overseeing weights and measures was carried out by the Office of Standard Weights and Measures, president Theodore Roosevelt appointed Samuel W. Stratton as the first director. The budget for the first year of operation was $40,000, a laboratory site was constructed in Washington, DC, and instruments were acquired from the national physical laboratories of Europe. In addition to weights and measures, the Bureau developed instruments for electrical units, in 1905 a meeting was called that would be the first National Conference on Weights and Measures. Quality standards were developed for products including some types of clothing, automobile brake systems and headlamps, antifreeze, during World War I, the Bureau worked on multiple problems related to war production, even operating its own facility to produce optical glass when European supplies were cut off. Between the wars, Harry Diamond of the Bureau developed a blind approach radio aircraft landing system, in 1948, financed by the Air Force, the Bureau began design and construction of SEAC, the Standards Eastern Automatic Computer. The computer went into operation in May 1950 using a combination of vacuum tubes, about the same time the Standards Western Automatic Computer, was built at the Los Angeles office of the NBS and used for research there. A mobile version, DYSEAC, was built for the Signal Corps in 1954, due to a changing mission, the National Bureau of Standards became the National Institute of Standards and Technology in 1988. Following 9/11, NIST conducted the investigation into the collapse of the World Trade Center buildings. NIST had a budget for fiscal year 2007 of about $843.3 million. NISTs 2009 budget was $992 million, and it also received $610 million as part of the American Recovery, NIST employs about 2,900 scientists, engineers, technicians, and support and administrative personnel. About 1,800 NIST associates complement the staff, in addition, NIST partners with 1,400 manufacturing specialists and staff at nearly 350 affiliated centers around the country. NIST publishes the Handbook 44 that provides the Specifications, tolerances, the Congress of 1866 made use of the metric system in commerce a legally protected activity through the passage of Metric Act of 1866. NIST is headquartered in Gaithersburg, Maryland, and operates a facility in Boulder, nISTs activities are organized into laboratory programs and extramural programs. Effective October 1,2010, NIST was realigned by reducing the number of NIST laboratory units from ten to six, nISTs Boulder laboratories are best known for NIST‑F1, which houses an atomic clock. NIST‑F1 serves as the source of the official time. NIST also operates a neutron science user facility, the NIST Center for Neutron Research, the NCNR provides scientists access to a variety of neutron scattering instruments, which they use in many research fields
NIST
–
Chart of NBS activities, 1915.
NIST
–
National Institute of Standards and Technology (NIST)
NIST
–
A spectrometer in use at the NBS in 1948.
NIST
–
Advanced Measurement Laboratory Complex in Gaithersburg
3.
System of measurement
–
A system of measurement is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce, systems of measurement in modern use include the metric system, the imperial system, and United States customary units. The French Revolution gave rise to the system, and this has spread around the world. In most systems, length, mass, and time are base quantities, later science developments showed that either electric charge or electric current could be added to extend the set of base quantities by which many other metrological units could be easily defined. Other quantities, such as power and speed, are derived from the set, for example. Such arrangements were satisfactory in their own contexts, the preference for a more universal and consistent system only gradually spread with the growth of science. Changing a measurement system has substantial financial and cultural costs which must be offset against the advantages to be obtained using a more rational system. However pressure built up, including scientists and engineers for conversion to a more rational. The unifying characteristic is that there was some definition based on some standard, eventually cubits and strides gave way to customary units to met the needs of merchants and scientists. In the metric system and other recent systems, a basic unit is used for each base quantity. Often secondary units are derived from the units by multiplying by powers of ten. Thus the basic unit of length is the metre, a distance of 1.234 m is 1,234 millimetres. Metrication is complete or nearly complete in almost all countries, US customary units are heavily used in the United States and to some degree in Liberia. Traditional Burmese units of measurement are used in Burma, U. S. units are used in limited contexts in Canada due to the large volume of trade, there is also considerable use of Imperial weights and measures, despite de jure Canadian conversion to metric. In the United States, metric units are used almost universally in science, widely in the military, and partially in industry, but customary units predominate in household use. At retail stores, the liter is a used unit for volume, especially on bottles of beverages. Some other standard non-SI units are still in use, such as nautical miles and knots in aviation. Metric systems of units have evolved since the adoption of the first well-defined system in France in 1795, during this evolution the use of these systems has spread throughout the world, first to non-English-speaking countries, and then to English speaking countries
System of measurement
–
A baby bottle that measures in three measurement systems—imperial (UK), US customary, and metric.
4.
SI derived unit
–
The International System of Units specifies a set of seven base units from which all other SI units of measurement are derived. Each of these units is either dimensionless or can be expressed as a product of powers of one or more of the base units. For example, the SI derived unit of area is the metre. The degree Celsius has an unclear status, and is arguably an exception to this rule. The names of SI units are written in lowercase, the symbols for units named after persons, however, are always written with an uppercase initial letter. In addition to the two dimensionless derived units radian and steradian,20 other derived units have special names, some other units such as the hour, litre, tonne, bar and electronvolt are not SI units, but are widely used in conjunction with SI units. Until 1995, the SI classified the radian and the steradian as supplementary units, but this designation was abandoned, International System of Quantities International System of Units International Vocabulary of Metrology Metric prefix Metric system Non-SI units mentioned in the SI Planck units SI base unit I. Mills, Tomislav Cvitas, Klaus Homann, Nikola Kallay, IUPAC, Quantities, Units and Symbols in Physical Chemistry. CS1 maint, Multiple names, authors list
SI derived unit
–
Base units
5.
Electric potential
–
An electric potential is the amount of work needed to move a unit positive charge from a reference point to a specific point inside the field without producing any acceleration. Typically, the point is Earth or a point at Infinity. By dividing out the charge on the particle a remainder is obtained that is a property of the field itself. This value can be calculated in either a static or an electric field at a specific time in units of joules per coulomb. The electric potential at infinity is assumed to be zero, a generalized electric scalar potential is also used in electrodynamics when time-varying electromagnetic fields are present, but this can not be so simply calculated. The electric potential and the vector potential together form a four vector. Classical mechanics explores concepts such as force, energy, potential etc, force and potential energy are directly related. A net force acting on any object will cause it to accelerate, as it rolls downhill its potential energy decreases, being translated to motion, inertial energy. It is possible to define the potential of certain force fields so that the energy of an object in that field depends only on the position of the object with respect to the field. Two such force fields are the field and an electric field. Such fields must affect objects due to the properties of the object. Objects may possess a property known as charge and an electric field exerts a force on charged objects. If the charged object has a charge the force will be in the direction of the electric field vector at that point while if the charge is negative the force will be in the opposite direction. The magnitude of the force is given by the quantity of the charge multiplied by the magnitude of the field vector. The electric potential at a point r in an electric field E is given by the line integral where C is an arbitrary path connecting the point with zero potential to r. When the curl ∇ × E is zero, the integral above does not depend on the specific path C chosen. The concept of electric potential is linked with potential energy. A test charge q has a potential energy UE given by U E = q V
Electric potential
–
Electromagnetism
Electric potential
–
The electric potential created by a charge Q is V = Q /(4πε o r). Different values of Q will make different values of electric potential V (shown in the image).
6.
Electromotive force
–
Electromotive force, also called emf, is the voltage developed by any source of electrical energy such as a battery or dynamo. It is generally defined as the potential for a source in a circuit. A device that supplies electrical energy is called electromotive force or emf, emfs convert chemical, mechanical, and other forms of energy into electrical energy. The product of such a device is known as emf. The word force in case is not used to mean mechanical force, measured in newtons. In electromagnetic induction, emf can be defined around a loop as the electromagnetic work that would be done on a charge if it travels once around that loop. This potential difference can drive a current if a circuit is attached to the terminals. Devices that can provide emf include electrochemical cells, thermoelectric devices, solar cells, photodiodes, electrical generators, transformer, in nature, emf is generated whenever magnetic field fluctuations occur through a surface. The shifting of the Earths magnetic field during a geomagnetic storm, … By chemical, mechanical or other means, the source of emf performs work dW on that charge to move it to the high potential terminal. The emf ℰ of the source is defined as the work dW done per charge dq, in the open-circuit case, charge separation continues until the electrical field from the separated charges is sufficient to arrest the reactions. Again the emf is countered by the voltage due to charge separation. If a load is attached, this voltage can drive a current, the general principle governing the emf in such electrical machines is Faradays law of induction. Electromotive force is often denoted by E or ℰ, in a device without internal resistance, if an electric charge Q passes through that device, and gains an energy W, the net emf for that device is the energy gained per unit charge, or J/Q. Like other measures of energy per charge, emf has SI units of volts, Electromotive force in electrostatic units is the statvolt. Inside a source of emf that is open-circuited, the electrostatic field created by separation of charge exactly cancels the forces producing the emf. Thus, the emf has the same value but opposite sign as the integral of the field aligned with an internal path between two terminals A and B of a source of emf in open-circuit condition. This equation applies only to locations A and B that are terminals and this equation involves the electrostatic electric field due to charge separation Ecs and does not involve any non-conservative component of electric field due to Faradays law of induction. The electrostatic field does not contribute to the net emf around a circuit because the portion of the electric field is conservative
Electromotive force
–
A typical reaction path requires the initial reactants to cross an energy barrier, enter an intermediate state and finally emerge in a lower energy configuration. If charge separation is involved, this energy difference can result in an emf. See Bergmann et al. and
Transition state.
Electromotive force
–
Solar cell voltage as a function of solar cell current delivered to a load for two light-induced currents I L; currents as a ratio with reverse saturation current I 0. Compare with Fig. 1.4 in Nelson.
7.
Alessandro Volta
–
He invented the Voltaic pile in 1799, and reported the results of his experiments in 1800 in a two-part letter to the President of the Royal Society. With this invention Volta proved that electricity could be generated chemically, Voltas invention sparked a great amount of scientific excitement and led others to conduct similar experiments which eventually led to the development of the field of electrochemistry. Alessandro Volta also drew admiration from Napoleon Bonaparte for his invention, Volta enjoyed a certain amount of closeness with the Emperor throughout his life and he was conferred numerous honours by him. Alessandro Volta held the chair of physics at the University of Pavia for nearly 40 years and was widely idolised by his students. Despite his professional success, Volta tended to be a person inclined towards domestic life, at this time he tended to live secluded from public life and more for the sake of his family until his eventual death in 1827 from a series of illnesses which began in 1823. The SI unit of electric potential is named in his honour as the volt, Volta was born in Como, a town in present-day northern Italy, on 18 February 1745. In 1794, Volta married a lady also from Como, Teresa Peregrini. His father, Filippo Volta, was of noble lineage and his mother, Donna Maddalena, came from the family of the Inzaghis. In 1774, he became a professor of physics at the Royal School in Como, a year later, he improved and popularised the electrophorus, a device that produced static electricity. In 1777, he travelled through Switzerland, there he befriended H. B. de Saussure. In the years between 1776 and 1778, Volta studied the chemistry of gases and he researched and discovered methane after reading a paper by Benjamin Franklin of the United States on flammable air. In November 1776, he found methane at Lake Maggiore, and he devised experiments such as the ignition of methane by an electric spark in a closed vessel. Volta also studied what we now call electrical capacitance, developing separate means to both electrical potential and charge, and discovering that for a given object, they are proportional. This is called Voltas Law of Capacitance, and it was for work the unit of electrical potential has been named the volt. In 1779 he became a professor of physics at the University of Pavia. Luigi Galvani, an Italian physicist, discovered something he named animal electricity when two different metals were connected in series with a leg and to one another. Volta realised that the frogs leg served as both a conductor of electricity and as a detector of electricity and he replaced the frogs leg with brine-soaked paper, and detected the flow of electricity by other means familiar to him from his previous studies. This may be called Voltas Law of the electrochemical series, Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and copper
Alessandro Volta
–
Alessandro Giuseppe Antonio Anastasio Volta
Alessandro Volta
–
Luigi Galvani, Volta's rival.
Alessandro Volta
–
Volta explains the principle of the "electric column" to
Napoleon in 1801.
8.
SI base unit
–
The International System of Units defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science, thus, the kelvin, named after Lord Kelvin, has the symbol K and the ampere, named after André-Marie Ampère, has the symbol A. Many other units, such as the litre, are not part of the SI. The definitions of the units have been modified several times since the Metre Convention in 1875. Since the redefinition of the metre in 1960, the kilogram is the unit that is directly defined in terms of a physical artifact. However, the mole, the ampere, and the candela are linked through their definitions to the mass of the platinum–iridium cylinder stored in a vault near Paris. It has long been an objective in metrology to define the kilogram in terms of a fundamental constant, two possibilities have attracted particular attention, the Planck constant and the Avogadro constant. The 23rd CGPM decided to postpone any formal change until the next General Conference in 2011
SI base unit
–
The seven SI base units and the interdependency of their definitions: for example, to extract the definition of the metre from the
speed of light, the definition of the second must be known while the
ampere and
candela are both dependent on the definition of
energy which in turn is defined in terms of
length,
mass and
time.
9.
Kilogram
–
The kilogram or kilogramme is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype of the Kilogram. The avoirdupois pound, used in both the imperial and US customary systems, is defined as exactly 0.45359237 kg, making one kilogram approximately equal to 2.2046 avoirdupois pounds. Other traditional units of weight and mass around the world are also defined in terms of the kilogram, the gram, 1/1000 of a kilogram, was provisionally defined in 1795 as the mass of one cubic centimeter of water at the melting point of ice. The final kilogram, manufactured as a prototype in 1799 and from which the IPK was derived in 1875, had an equal to the mass of 1 dm3 of water at its maximum density. The kilogram is the only SI base unit with an SI prefix as part of its name and it is also the only SI unit that is still directly defined by an artifact rather than a fundamental physical property that can be reproduced in different laboratories. Three other base units and 17 derived units in the SI system are defined relative to the kilogram, only 8 other units do not require the kilogram in their definition, temperature, time and frequency, length, and angle. At its 2011 meeting, the CGPM agreed in principle that the kilogram should be redefined in terms of the Planck constant, the decision was originally deferred until 2014, in 2014 it was deferred again until the next meeting. There are currently several different proposals for the redefinition, these are described in the Proposed Future Definitions section below, the International Prototype Kilogram is rarely used or handled. In the decree of 1795, the term gramme thus replaced gravet, the French spelling was adopted in the United Kingdom when the word was used for the first time in English in 1797, with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with kilogram having become by far the more common, UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling. In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has used to mean both kilogram and kilometer. In 1935 this was adopted by the IEC as the Giorgi system, now known as MKS system. In 1948 the CGPM commissioned the CIPM to make recommendations for a practical system of units of measurement. This led to the launch of SI in 1960 and the subsequent publication of the SI Brochure, the kilogram is a unit of mass, a property which corresponds to the common perception of how heavy an object is. Mass is a property, that is, it is related to the tendency of an object at rest to remain at rest, or if in motion to remain in motion at a constant velocity. Accordingly, for astronauts in microgravity, no effort is required to hold objects off the cabin floor, they are weightless. However, since objects in microgravity still retain their mass and inertia, the ratio of the force of gravity on the two objects, measured by the scale, is equal to the ratio of their masses. On April 7,1795, the gram was decreed in France to be the weight of a volume of pure water equal to the cube of the hundredth part of the metre
Kilogram
–
A domestic-quality one-kilogram weight made of
cast iron (the
credit card is for scale). The shape follows
OIML recommendation R52 for cast-iron hexagonal weights
Kilogram
–
Measurement of weight – gravitational attraction of the measurand causes a distortion of the spring
Kilogram
–
Measurement of mass – the gravitational force on the measurand is balanced against the gravitational force on the weights.
Kilogram
–
The Arago kilogram, an exact copy of the "Kilogramme des Archives" commissioned in 1821 by the US under supervision of French physicist
François Arago that served as the US's first kilogram standard of mass until 1889, when the US converted to primary metric standards and received its current kilogram prototypes, K4 and K20.
10.
Metre
–
The metre or meter, is the base unit of length in the International System of Units. The metre is defined as the length of the path travelled by light in a vacuum in 1/299792458 seconds, the metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a metre bar. In 1960, the metre was redefined in terms of a number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted, the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Measuring devices are spelled -meter in all variants of English, the suffix -meter has the same Greek origin as the unit of length. This range of uses is found in Latin, French, English. Thus calls for measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. In 1668, Wilkins proposed using Christopher Wrens suggestion of defining the metre using a pendulum with a length which produced a half-period of one second, christiaan Huygens had observed that length to be 38 Rijnland inches or 39.26 English inches. This is the equivalent of what is now known to be 997 mm, no official action was taken regarding this suggestion. In the 18th century, there were two approaches to the definition of the unit of length. One favoured Wilkins approach, to define the metre in terms of the length of a pendulum which produced a half-period of one second. The other approach was to define the metre as one ten-millionth of the length of a quadrant along the Earths meridian, that is, the distance from the Equator to the North Pole. This means that the quadrant would have defined as exactly 10000000 metres at that time. To establish a universally accepted foundation for the definition of the metre, more measurements of this meridian were needed. This portion of the meridian, assumed to be the length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator
Metre
–
Belfry, Dunkirk —the northern end of the meridian arc
Metre
Metre
–
Fortress of Montjuïc —the southerly end of the meridian arc
Metre
–
Creating the metre-alloy in 1874 at the Conservatoire des Arts et Métiers. Present Henri Tresca, George Matthey, Saint-Claire Deville and Debray
11.
Second
–
The second is the base unit of time in the International System of Units. It is qualitatively defined as the division of the hour by sixty. SI definition of second is the duration of 9192631770 periods of the corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. Seconds may be measured using a mechanical, electrical or an atomic clock, SI prefixes are combined with the word second to denote subdivisions of the second, e. g. the millisecond, the microsecond, and the nanosecond. Though SI prefixes may also be used to form multiples of the such as kilosecond. The second is also the unit of time in other systems of measurement, the centimetre–gram–second, metre–kilogram–second, metre–tonne–second. Absolute zero implies no movement, and therefore zero external radiation effects, the second thus defined is consistent with the ephemeris second, which was based on astronomical measurements. The realization of the second is described briefly in a special publication from the National Institute of Standards and Technology. 1 international second is equal to, 1⁄60 minute 1⁄3,600 hour 1⁄86,400 day 1⁄31,557,600 Julian year 1⁄, more generally, = 1⁄, the Hellenistic astronomers Hipparchus and Ptolemy subdivided the day into sixty parts. They also used an hour, simple fractions of an hour. No sexagesimal unit of the day was used as an independent unit of time. The modern second is subdivided using decimals - although the third remains in some languages. The earliest clocks to display seconds appeared during the last half of the 16th century, the second became accurately measurable with the development of mechanical clocks keeping mean time, as opposed to the apparent time displayed by sundials. The earliest spring-driven timepiece with a hand which marked seconds is an unsigned clock depicting Orpheus in the Fremersdorf collection. During the 3rd quarter of the 16th century, Taqi al-Din built a clock with marks every 1/5 minute, in 1579, Jost Bürgi built a clock for William of Hesse that marked seconds. In 1581, Tycho Brahe redesigned clocks that displayed minutes at his observatory so they also displayed seconds, however, they were not yet accurate enough for seconds. In 1587, Tycho complained that his four clocks disagreed by plus or minus four seconds, in 1670, London clockmaker William Clement added this seconds pendulum to the original pendulum clock of Christiaan Huygens. From 1670 to 1680, Clement made many improvements to his clock and this clock used an anchor escapement mechanism with a seconds pendulum to display seconds in a small subdial
Second
–
FOCS 1, a continuous cold caesium fountain atomic clock in Switzerland, started operating in 2004 at an uncertainty of one second in 30 million years.
Second
–
Key concepts
12.
Ampere
–
The ampere, often shortened to amp, is a unit of electric current. In the International System of Units the ampere is one of the seven SI base units and it is named after André-Marie Ampère, French mathematician and physicist, considered the father of electrodynamics. SI defines the ampere in terms of base units by measuring the electromagnetic force between electrical conductors carrying electric current. The ampere was then defined as one coulomb of charge per second, in SI, the unit of charge, the coulomb, is defined as the charge carried by one ampere during one second. In the future, the SI definition may shift back to charge as the base unit, ampères force law states that there is an attractive or repulsive force between two parallel wires carrying an electric current. This force is used in the definition of the ampere. The SI unit of charge, the coulomb, is the quantity of electricity carried in 1 second by a current of 1 ampere, conversely, a current of one ampere is one coulomb of charge going past a given point per second,1 A =1 C s. In general, charge Q is determined by steady current I flowing for a time t as Q = It, constant, instantaneous and average current are expressed in amperes and the charge accumulated, or passed through a circuit over a period of time is expressed in coulombs. The relation of the ampere to the coulomb is the same as that of the watt to the joule, the ampere was originally defined as one tenth of the unit of electric current in the centimetre–gram–second system of units. That unit, now known as the abampere, was defined as the amount of current that generates a force of two dynes per centimetre of length between two wires one centimetre apart. The size of the unit was chosen so that the derived from it in the MKSA system would be conveniently sized. The international ampere was a realization of the ampere, defined as the current that would deposit 0.001118 grams of silver per second from a silver nitrate solution. Later, more accurate measurements revealed that this current is 0.99985 A, at present, techniques to establish the realization of an ampere have a relative uncertainty of approximately a few parts in 107, and involve realizations of the watt, the ohm and the volt. Rather than a definition in terms of the force between two current-carrying wires, it has proposed that the ampere should be defined in terms of the rate of flow of elementary charges. Since a coulomb is equal to 6. 2415093×1018 elementary charges. The proposed change would define 1 A as being the current in the direction of flow of a number of elementary charges per second. In 2005, the International Committee for Weights and Measures agreed to study the proposed change, the new definition was discussed at the 25th General Conference on Weights and Measures in 2014 but for the time being was not adopted. The current drawn by typical constant-voltage energy distribution systems is usually dictated by the power consumed by the system, for this reason the examples given below are grouped by voltage level
Ampere
–
Demonstration model of a moving iron ammeter. As the current through the coil increases, the plunger is drawn further into the coil and the pointer deflects to the right.
13.
Electric potential difference
–
Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential energy between two points per unit electric charge. The voltage between two points is equal to the work done per unit of charge against an electric field to move the test charge between two points. This is measured in units of volts, voltage can be caused by static electric fields, by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these three. A voltmeter can be used to measure the voltage between two points in a system, often a reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy or lost, used, given two points in space, x A and x B, voltage is the difference in electric potential between those two points. Electric potential must be distinguished from electric energy by noting that the potential is a per-unit-charge quantity. Like mechanical potential energy, the zero of electric potential can be chosen at any point, so the difference in potential, i. e. the voltage, is the quantity which is physically meaningful. The voltage between point A to point B is equal to the work which would have to be done, per unit charge, against or by the electric field to move the charge from A to B. The voltage between the two ends of a path is the energy required to move a small electric charge along that path. Mathematically this is expressed as the integral of the electric field. In the general case, both an electric field and a dynamic electromagnetic field must be included in determining the voltage between two points. Historically this quantity has also called tension and pressure. Pressure is now obsolete but tension is used, for example within the phrase high tension which is commonly used in thermionic valve based electronics. Voltage is defined so that negatively charged objects are pulled towards higher voltages, therefore, the conventional current in a wire or resistor always flows from higher voltage to lower voltage. Current can flow from lower voltage to higher voltage, but only when a source of energy is present to push it against the electric field. This is the case within any electric power source, for example, inside a battery, chemical reactions provide the energy needed for ion current to flow from the negative to the positive terminal. The electric field is not the only factor determining charge flow in a material, the electric potential of a material is not even a well defined quantity, since it varies on the subatomic scale. A more convenient definition of voltage can be found instead in the concept of Fermi level, in this case the voltage between two bodies is the thermodynamic work required to move a unit of charge between them
Electric potential difference
–
Batteries are sources of voltage in many
electric circuits
Electric potential difference
–
Working on
high voltage power lines
Electric potential difference
–
Multimeter set to measure voltage
14.
Voltage
–
Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential energy between two points per unit electric charge. The voltage between two points is equal to the work done per unit of charge against an electric field to move the test charge between two points. This is measured in units of volts, voltage can be caused by static electric fields, by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these three. A voltmeter can be used to measure the voltage between two points in a system, often a reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy or lost, used, given two points in space, x A and x B, voltage is the difference in electric potential between those two points. Electric potential must be distinguished from electric energy by noting that the potential is a per-unit-charge quantity. Like mechanical potential energy, the zero of electric potential can be chosen at any point, so the difference in potential, i. e. the voltage, is the quantity which is physically meaningful. The voltage between point A to point B is equal to the work which would have to be done, per unit charge, against or by the electric field to move the charge from A to B. The voltage between the two ends of a path is the energy required to move a small electric charge along that path. Mathematically this is expressed as the integral of the electric field. In the general case, both an electric field and a dynamic electromagnetic field must be included in determining the voltage between two points. Historically this quantity has also called tension and pressure. Pressure is now obsolete but tension is used, for example within the phrase high tension which is commonly used in thermionic valve based electronics. Voltage is defined so that negatively charged objects are pulled towards higher voltages, therefore, the conventional current in a wire or resistor always flows from higher voltage to lower voltage. Current can flow from lower voltage to higher voltage, but only when a source of energy is present to push it against the electric field. This is the case within any electric power source, for example, inside a battery, chemical reactions provide the energy needed for ion current to flow from the negative to the positive terminal. The electric field is not the only factor determining charge flow in a material, the electric potential of a material is not even a well defined quantity, since it varies on the subatomic scale. A more convenient definition of voltage can be found instead in the concept of Fermi level, in this case the voltage between two bodies is the thermodynamic work required to move a unit of charge between them
Voltage
–
Batteries are sources of voltage in many
electric circuits
Voltage
–
Working on
high voltage power lines
Voltage
–
Multimeter set to measure voltage
15.
Electrical conductor
–
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electrical conductors, Electrical current is generated by the flow of negatively charged electrons, positively charged holes, and positive or negative ions in some cases. In order for current to flow, it is not necessary for one charged particle to travel from the producing the current to that consuming it. Instead, the particle simply needs to nudge its neighbor a finite amount who will nudge its neighbor and on and on until a particle is nudged into the consumer. Essentially what is occurring here is a chain of momentum transfer between mobile charge carriers, the Drude model of conduction describes this process more rigorously. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents, the resistance of a given conductor depends on the material it is made of, and on its dimensions. For a given material, the resistance is proportional to the cross-sectional area. For example, a copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a material, the resistance is proportional to the length, for example. The resistance R and conductance G of a conductor of uniform cross section, therefore, the resistivity and conductivity are proportionality constants, and therefore depend only on the material the wire is made of, not the geometry of the wire. Resistivity and conductivity are reciprocals, ρ =1 / σ, resistivity is a measure of the materials ability to oppose electric current. This formula is not exact, It assumes the current density is uniform in the conductor. However, this still provides a good approximation for long thin conductors such as wires. Another situation this formula is not exact for is with alternating current, then, the geometrical cross-section is different from the effective cross-section in which current actually flows, so the resistance is higher than expected. Similarly, if two conductors are each other carrying AC current, their resistances increase due to the proximity effect. Aside from the geometry of the wire, temperature also has a significant effect on the efficacy of conductors, temperature affects conductors in two main ways, the first is that materials may expand under the application of heat. The amount that the material will expand is governed by the expansion coefficient specific to the material. Such an expansion will change the geometry of the conductor and therefore its characteristic resistance, however, this effect is generally small, on the order of 10−6
Electrical conductor
–
Overhead conductors carry electric power from generating stations to customers.
16.
Electric current
–
An electric current is a flow of electric charge. In electric circuits this charge is carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas. The SI unit for measuring a current is the ampere. Electric current is measured using a device called an ammeter, electric currents cause Joule heating, which creates light in incandescent light bulbs. They also create magnetic fields, which are used in motors, inductors and generators, the particles that carry the charge in an electric current are called charge carriers. In metals, one or more electrons from each atom are loosely bound to the atom and these conduction electrons are the charge carriers in metal conductors. The conventional symbol for current is I, which originates from the French phrase intensité de courant, current intensity is often referred to simply as current. The I symbol was used by André-Marie Ampère, after whom the unit of current is named, in formulating the eponymous Ampères force law. The notation travelled from France to Great Britain, where it became standard, in a conductive material, the moving charged particles which constitute the electric current are called charge carriers. In other materials, notably the semiconductors, the carriers can be positive or negative. Positive and negative charge carriers may even be present at the same time, a flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the opposite direction. Since current can be the flow of positive or negative charges. The direction of current is arbitrarily defined as the same direction as positive charges flow. This is called the direction of current I. If the current flows in the direction, the variable I has a negative value. When analyzing electrical circuits, the direction of current through a specific circuit element is usually unknown. Consequently, the directions of currents are often assigned arbitrarily
Electric current
–
A simple electric circuit, where current is represented by the letter i. The relationship between the voltage (V), resistance (R), and current (I) is V=IR; this is known as
Ohm's Law.
17.
Power (physics)
–
In physics, power is the rate of doing work. It is the amount of energy consumed per unit time, having no direction, it is a scalar quantity. In the SI system, the unit of power is the joule per second, known as the watt in honour of James Watt, another common and traditional measure is horsepower. Being the rate of work, the equation for power can be written, because this integral depends on the trajectory of the point of application of the force and torque, this calculation of work is said to be path dependent. As a physical concept, power requires both a change in the universe and a specified time in which the change occurs. This is distinct from the concept of work, which is measured in terms of a net change in the state of the physical universe. The output power of a motor is the product of the torque that the motor generates. The power involved in moving a vehicle is the product of the force of the wheels. The dimension of power is divided by time. The SI unit of power is the watt, which is equal to one joule per second, other units of power include ergs per second, horsepower, metric horsepower, and foot-pounds per minute. One horsepower is equivalent to 33,000 foot-pounds per minute, or the required to lift 550 pounds by one foot in one second. Other units include dBm, a logarithmic measure with 1 milliwatt as reference, food calories per hour, Btu per hour. This shows how power is an amount of energy consumed per unit time. If ΔW is the amount of work performed during a period of time of duration Δt and it is the average amount of work done or energy converted per unit of time. The average power is simply called power when the context makes it clear. The instantaneous power is then the value of the average power as the time interval Δt approaches zero. P = lim Δ t →0 P a v g = lim Δ t →0 Δ W Δ t = d W d t. In the case of constant power P, the amount of work performed during a period of duration T is given by, W = P t
Power (physics)
–
Ansel Adams photograph of electrical wires of the Boulder Dam Power Units, 1941–1942
18.
Meter
–
The metre or meter, is the base unit of length in the International System of Units. The metre is defined as the length of the path travelled by light in a vacuum in 1/299792458 seconds, the metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a metre bar. In 1960, the metre was redefined in terms of a number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted, the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Measuring devices are spelled -meter in all variants of English, the suffix -meter has the same Greek origin as the unit of length. This range of uses is found in Latin, French, English. Thus calls for measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. In 1668, Wilkins proposed using Christopher Wrens suggestion of defining the metre using a pendulum with a length which produced a half-period of one second, christiaan Huygens had observed that length to be 38 Rijnland inches or 39.26 English inches. This is the equivalent of what is now known to be 997 mm, no official action was taken regarding this suggestion. In the 18th century, there were two approaches to the definition of the unit of length. One favoured Wilkins approach, to define the metre in terms of the length of a pendulum which produced a half-period of one second. The other approach was to define the metre as one ten-millionth of the length of a quadrant along the Earths meridian, that is, the distance from the Equator to the North Pole. This means that the quadrant would have defined as exactly 10000000 metres at that time. To establish a universally accepted foundation for the definition of the metre, more measurements of this meridian were needed. This portion of the meridian, assumed to be the length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator
Meter
–
Belfry, Dunkirk —the northern end of the meridian arc
Meter
–
Fortress of Montjuïc —the southerly end of the meridian arc
Meter
–
Creating the metre-alloy in 1874 at the Conservatoire des Arts et Métiers. Present Henri Tresca, George Matthey, Saint-Claire Deville and Debray
Meter
–
Closeup of National Prototype Metre Bar No. 27, made in 1889 by the
International Bureau of Weights and Measures (BIPM) and given to the United States, which served as the standard for defining all units of length in the US from 1893 to 1960
19.
Electric field
–
An electric field is a vector field that associates to each point in space the Coulomb force that would be experienced per unit of electric charge, by an infinitesimal test charge at that point. Electric fields are created by electric charges and can be induced by time-varying magnetic fields, the electric field combines with the magnetic field to form the electromagnetic field. The electric field, E, at a point is defined as the force, F. A particle of charge q would be subject to a force F = q E and its SI units are newtons per coulomb or, equivalently, volts per metre, which in terms of SI base units are kg⋅m⋅s−3⋅A−1. Electric fields are caused by electric charges or varying magnetic fields, in the special case of a steady state, the Maxwell-Faraday inductive effect disappears. The resulting two equations, taken together, are equivalent to Coulombs law, written as E =14 π ε0 ∫ d r ′ ρ r − r ′ | r − r ′ |3 for a charge density ρ. Notice that ε0, the permittivity of vacuum, must be substituted if charges are considered in non-empty media, the equations of electromagnetism are best described in a continuous description. A charge q located at r 0 can be described mathematically as a charge density ρ = q δ, conversely, a charge distribution can be approximated by many small point charges. Electric fields satisfy the principle, because Maxwells equations are linear. This principle is useful to calculate the field created by point charges. Q n are stationary in space at r 1, r 2, in that case, Coulombs law fully describes the field. If a system is static, such that magnetic fields are not time-varying, then by Faradays law, in this case, one can define an electric potential, that is, a function Φ such that E = − ∇ Φ. This is analogous to the gravitational potential, Coulombs law, which describes the interaction of electric charges, F = q = q E is similar to Newtons law of universal gravitation, F = m = m g. This suggests similarities between the electric field E and the gravitational field g, or their associated potentials, mass is sometimes called gravitational charge because of that similarity. Electrostatic and gravitational forces both are central, conservative and obey an inverse-square law, a uniform field is one in which the electric field is constant at every point. It can be approximated by placing two conducting plates parallel to other and maintaining a voltage between them, it is only an approximation because of boundary effects. Assuming infinite planes, the magnitude of the electric field E is, electrodynamic fields are E-fields which do change with time, for instance when charges are in motion. The electric field cannot be described independently of the field in that case
Electric field
–
Electric field lines emanating from a point positive
electric charge suspended over an infinite sheet of conducting material.
20.
Newton (unit)
–
The newton is the International System of Units derived unit of force. It is named after Isaac Newton in recognition of his work on classical mechanics, see below for the conversion factors. One newton is the force needed to one kilogram of mass at the rate of one metre per second squared in direction of the applied force. In 1948, the 9th CGPM resolution 7 adopted the name newton for this force, the MKS system then became the blueprint for todays SI system of units. The newton thus became the unit of force in le Système International dUnités. This SI unit is named after Isaac Newton, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, section 5.2. Newtons second law of motion states that F = ma, where F is the applied, m is the mass of the object receiving the force. The newton is therefore, where the symbols are used for the units, N for newton, kg for kilogram, m for metre. In dimensional analysis, F = M L T2 where F is force, M is mass, L is length, at average gravity on earth, a kilogram mass exerts a force of about 9.8 newtons. An average-sized apple exerts about one newton of force, which we measure as the apples weight, for example, the tractive effort of a Class Y steam train and the thrust of an F100 fighter jet engine are both around 130 kN. One kilonewton,1 kN, is 102.0 kgf,1 kN =102 kg ×9.81 m/s2 So for example, a platform rated at 321 kilonewtons will safely support a 32,100 kilograms load. Specifications in kilonewtons are common in safety specifications for, the values of fasteners, Earth anchors. Working loads in tension and in shear, thrust of rocket engines and launch vehicles clamping forces of the various moulds in injection moulding machines used to manufacture plastic parts
Newton (unit)
–
Base units
21.
Coulomb
–
The coulomb is the International System of Units unit of electric charge. 242×1018 protons, and −1 C is equivalent to the charge of approximately 6. 242×1018 electrons. This SI unit is named after Charles-Augustin de Coulomb, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, the SI system defines the coulomb in terms of the ampere and second,1 C =1 A ×1 s. The second is defined in terms of a frequency emitted by caesium atoms. The ampere is defined using Ampères force law, the definition relies in part on the mass of the prototype kilogram. In practice, the balance is used to measure amperes with the highest possible accuracy. One coulomb is the magnitude of charge in 6. 24150934×10^18 protons or electrons. The inverse of this gives the elementary charge of 1. 6021766208×10−19 C. The magnitude of the charge of one mole of elementary charges is known as a faraday unit of charge. In terms of Avogadros number, one coulomb is equal to approximately 1.036 × NA×10−5 elementary charges, one ampere-hour =3600 C,1 mA⋅h =3.6 C. One statcoulomb, the obsolete CGS electrostatic unit of charge, is approximately 3. 3356×10−10 C or about one-third of a nanocoulomb, the elementary charge, the charge of a proton, is approximately 1. 6021766208×10−19 C. In SI, the charge in coulombs is an approximate value. However, in other systems, the elementary charge has an exact value by definition. Specifically, e90 = / C exactly, SI itself may someday change its definitions in a similar way. For example, one possible proposed redefinition is the ampere. is such that the value of the charge e is exactly 1. 602176487×10−19 coulombs. This proposal is not yet accepted as part of the SI, the charges in static electricity from rubbing materials together are typically a few microcoulombs. The amount of charge that travels through a lightning bolt is typically around 15 C, the amount of charge that travels through a typical alkaline AA battery from being fully charged to discharged is about 5 kC =5000 C ≈1400 mA⋅h. The hydraulic analogy uses everyday terms to illustrate movement of charge, the analogy equates charge to a volume of water, and voltage to pressure
Coulomb
–
Base units
22.
Joule
–
The joule, symbol J, is a derived unit of energy in the International System of Units. It is equal to the transferred to an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre. It is also the energy dissipated as heat when a current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule, one joule can also be defined as, The work required to move an electric charge of one coulomb through an electrical potential difference of one volt, or one coulomb volt. This relationship can be used to define the volt, the work required to produce one watt of power for one second, or one watt second. This relationship can be used to define the watt and this SI unit is named after James Prescott Joule. As with every International System of Units unit named for a person, note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, section 5.2. The CGPM has given the unit of energy the name Joule, the use of newton metres for torque and joules for energy is helpful to avoid misunderstandings and miscommunications. The distinction may be also in the fact that energy is a scalar – the dot product of a vector force. By contrast, torque is a vector – the cross product of a distance vector, torque and energy are related to one another by the equation E = τ θ, where E is energy, τ is torque, and θ is the angle swept. Since radians are dimensionless, it follows that torque and energy have the same dimensions, one joule in everyday life represents approximately, The energy required to lift a medium-size tomato 1 m vertically from the surface of the Earth. The energy released when that same tomato falls back down to the ground, the energy required to accelerate a 1 kg mass at 1 m·s−2 through a 1 m distance in space. The heat required to raise the temperature of 1 g of water by 0.24 °C, the typical energy released as heat by a person at rest every 1/60 s. The kinetic energy of a 50 kg human moving very slowly, the kinetic energy of a 56 g tennis ball moving at 6 m/s. The kinetic energy of an object with mass 1 kg moving at √2 ≈1.4 m/s, the amount of electricity required to light a 1 W LED for 1 s. Since the joule is also a watt-second and the unit for electricity sales to homes is the kW·h. For additional examples, see, Orders of magnitude The zeptojoule is equal to one sextillionth of one joule,160 zeptojoules is equivalent to one electronvolt. The nanojoule is equal to one billionth of one joule, one nanojoule is about 1/160 of the kinetic energy of a flying mosquito
Joule
–
Base units
23.
Energy
–
In physics, energy is the property that must be transferred to an object in order to perform work on – or to heat – the object, and can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. Mass and energy are closely related, for example, with a sensitive enough scale, one could measure an increase in mass after heating an object. Living organisms require available energy to stay alive, such as the humans get from food. Civilisation gets the energy it needs from energy resources such as fuels, nuclear fuel. The processes of Earths climate and ecosystem are driven by the radiant energy Earth receives from the sun, the total energy of a system can be subdivided and classified in various ways. It may also be convenient to distinguish gravitational energy, thermal energy, several types of energy, electric energy. Many of these overlap, for instance, thermal energy usually consists partly of kinetic. Some types of energy are a mix of both potential and kinetic energy. An example is energy which is the sum of kinetic. Whenever physical scientists discover that a phenomenon appears to violate the law of energy conservation. Heat and work are special cases in that they are not properties of systems, in general we cannot measure how much heat or work are present in an object, but rather only how much energy is transferred among objects in certain ways during the occurrence of a given process. Heat and work are measured as positive or negative depending on which side of the transfer we view them from, the distinctions between different kinds of energy is not always clear-cut. In contrast to the definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness. The modern analog of this property, kinetic energy, differs from vis viva only by a factor of two, in 1807, Thomas Young was possibly the first to use the term energy instead of vis viva, in its modern sense. Gustave-Gaspard Coriolis described kinetic energy in 1829 in its modern sense, the law of conservation of energy was also first postulated in the early 19th century, and applies to any isolated system. It was argued for years whether heat was a physical substance, dubbed the caloric, or merely a physical quantity. In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat and these developments led to the theory of conservation of energy, formalized largely by William Thomson as the field of thermodynamics
Energy
–
In a typical
lightning strike, 500
megajoules of
electric potential energy is converted into the same amount of energy in other forms, mostly
light energy,
sound energy and
thermal energy.
Energy
–
Thermal energy is energy of microscopic constituents of matter, which may include both
kinetic and
potential energy.
Energy
–
Thomas Young – the first to use the term "energy" in the modern sense.
Energy
–
A
Turbo generator transforms the energy of pressurised steam into electrical energy
24.
Electronvolt
–
In physics, the electronvolt is a unit of energy equal to approximately 1. 6×10−19 joules. By definition, it is the amount of energy gained by the charge of an electron moving across an electric potential difference of one volt. Thus it is 1 volt multiplied by the elementary charge, therefore, one electronvolt is equal to 6981160217662079999♠1. 6021766208×10−19 J. The electronvolt is not a SI unit, and its definition is empirical, like the elementary charge on which it is based, it is not an independent quantity but is equal to 1 J/C √2hα / μ0c0. It is a unit of energy within physics, widely used in solid state, atomic, nuclear. It is commonly used with the metric prefixes milli-, kilo-, in some older documents, and in the name Bevatron, the symbol BeV is used, which stands for billion electronvolts, it is equivalent to the GeV. By mass–energy equivalence, the electronvolt is also a unit of mass and it is common in particle physics, where units of mass and energy are often interchanged, to express mass in units of eV/c2, where c is the speed of light in vacuum. It is common to express mass in terms of eV as a unit of mass. The mass equivalent of 1 eV/c2 is 1 eV / c 2 = ⋅1 V2 =1.783 ×10 −36 kg. For example, an electron and a positron, each with a mass of 0.511 MeV/c2, the proton has a mass of 0.938 GeV/c2. In general, the masses of all hadrons are of the order of 1 GeV/c2, the unified atomic mass unit,1 gram divided by Avogadros number, is almost the mass of a hydrogen atom, which is mostly the mass of the proton. To convert to megaelectronvolts, use the formula,1 u =931.4941 MeV/c2 =0.9314941 GeV/c2, in high-energy physics, the electronvolt is often used as a unit of momentum. A potential difference of 1 volt causes an electron to gain an amount of energy and this gives rise to usage of eV as units of momentum, for the energy supplied results in acceleration of the particle. The dimensions of units are LMT−1. The dimensions of units are L2MT−2. Then, dividing the units of energy by a constant that has units of velocity. In the field of particle physics, the fundamental velocity unit is the speed of light in vacuum c. Thus, dividing energy in eV by the speed of light, the fundamental velocity constant c is often dropped from the units of momentum by way of defining units of length such that the value of c is unity
Electronvolt
–
γ:
Gamma rays
25.
Josephson effect
–
The Josephson effect is the phenomenon of supercurrent—i. e. A current that flows indefinitely long without any voltage applied—across a device known as a Josephson junction, the weak link can consist of a thin insulating barrier, a short section of non-superconducting metal, or a physical constriction that weakens the superconductivity at the point of contact. The Josephson effect is an example of a quantum phenomenon. It is named after the British physicist Brian David Josephson, who predicted in 1962 the mathematical relationships for the current, the first paper to claim the discovery of Josephsons effect, and to make the requisite experimental checks, was that of Philip Anderson and John Rowell. These authors were awarded patents on the effects that were never enforced, before Josephsons prediction, it was only known that normal electrons can flow through an insulating barrier, by means of quantum tunneling. Josephson was the first to predict the tunneling of superconducting Cooper pairs, for this work, Josephson received the Nobel Prize in Physics in 1973. Josephson junctions have important applications in quantum-mechanical circuits, such as SQUIDs, superconducting qubits, the NIST standard for one volt is achieved by an array of 20,208 Josephson junctions in series. Types of Josephson junction include the pi Josephson junction, varphi Josephson junction, long Josephson junction, a Dayem bridge is a thin-film variant of the Josephson junction in which the weak link consists of a superconducting wire with dimensions on the scale of a few micrometres or less. The Josephson junction count of a device is used as a benchmark for its complexity and they are widely used in science and engineering. In precision metrology, the Josephson effect provides an exactly reproducible conversion between frequency and voltage, however, BIPM has not changed the official SI unit definition. Single-electron transistors are often constructed of superconducting materials, allowing use to be made of the Josephson effect to achieve novel effects, the resulting device is called a superconducting single-electron transistor. The Josephson effect is used for the most precise measurements of elementary charge in terms of the Josephson constant. RSFQ digital electronics is based on shunted Josephson junctions, Josephson junctions are integral in superconducting quantum computing as qubits such as in a flux qubit or others schemes where the phase and charge act as the conjugate variables. Superconducting tunnel junction detectors may become a replacement for CCDs for use in astronomy. These devices are effective across a spectrum from ultraviolet to infrared. The technology has been tried out on the William Herschel Telescope in the SCAM instrument, quiterons and similar superconducting switching devices. Josephson effect has also observed in SHeQUIDs, the superfluid helium analog of a dc-SQUID. The critical current is an important phenomenological parameter of the device that can be affected by temperature as well as by a magnetic field
Josephson effect
–
Josephson junction array chip developed by the
National Bureau of Standards as a standard volt
Josephson effect
–
Typical I-V characteristic of a
superconducting tunnel junction, a common kind of Josephson junction. The scale of the vertical axis is 50 μA and that of the horizontal one is 1 mV. The bar at represents the DC Josephson effect, while the current at large values of is due to the finite value of the superconductor bandgap and not reproduced by the above equations.
26.
Planck constant
–
The Planck constant is a physical constant that is the quantum of action, central in quantum mechanics. The light quantum behaved in some respects as a neutral particle. It was eventually called the photon, the Planck–Einstein relation connects the particulate photon energy E with its associated wave frequency f, E = h f This energy is extremely small in terms of ordinarily perceived everyday objects. Since the frequency f, wavelength λ, and speed of c are related by f = c λ. This leads to another relationship involving the Planck constant, with p denoting the linear momentum of a particle, the de Broglie wavelength λ of the particle is given by λ = h p. In applications where it is natural to use the frequency it is often useful to absorb a factor of 2π into the Planck constant. The resulting constant is called the reduced Planck constant or Dirac constant and it is equal to the Planck constant divided by 2π, and is denoted ħ, ℏ = h 2 π. The energy of a photon with angular frequency ω, where ω = 2πf, is given by E = ℏ ω, while its linear momentum relates to p = ℏ k and this was confirmed by experiments soon afterwards. This holds throughout quantum theory, including electrodynamics and these two relations are the temporal and spatial component parts of the special relativistic expression using 4-Vectors. P μ = = ℏ K μ = ℏ Classical statistical mechanics requires the existence of h, eventually, following upon Plancks discovery, it was recognized that physical action cannot take on an arbitrary value. Instead, it must be multiple of a very small quantity. This is the old quantum theory developed by Bohr and Sommerfeld, in which particle trajectories exist but are hidden. Thus there is no value of the action as classically defined, related to this is the concept of energy quantization which existed in old quantum theory and also exists in altered form in modern quantum physics. Classical physics cannot explain either quantization of energy or the lack of a particle motion. In many cases, such as for light or for atoms, quantization of energy also implies that only certain energy levels are allowed. The Planck constant has dimensions of physical action, i. e. energy multiplied by time, or momentum multiplied by distance, in SI units, the Planck constant is expressed in joule-seconds or or. The value of the Planck constant is, h =6.626070040 ×10 −34 J⋅s =4.135667662 ×10 −15 eV⋅s. The value of the reduced Planck constant is, ℏ = h 2 π =1.054571800 ×10 −34 J⋅s =6.582119514 ×10 −16 eV⋅s
Planck constant
–
Plaque at the
Humboldt University of Berlin: "Max Planck, discoverer of the elementary quantum of action h, taught in this building from 1889 to 1928."
27.
Hydraulic analogy
–
The electronic–hydraulic analogy is the most widely used analogy for electron fluid in a metal conductor. Since electric current is invisible and the processes at play in electronics are difficult to demonstrate. Electricity was originally understood to be a kind of fluid, as with all analogies, it demands an intuitive and competent understanding of the baseline paradigms. There is no unique paradigm for establishing this analogy, two paradigms can be used to introduce the concept to students, Version with pressure induced by gravity. Large tanks of water are held up high, or are filled to differing levels. This is reminiscent of electrical diagrams with an up arrow pointing to +V, grounded pins that otherwise are not shown connecting to anything and this has the advantage of associating electric potential with gravitational potential. Completely enclosed version with pumps providing pressure only, no gravity and this is reminiscent of a circuit diagram with a voltage source shown and the wires actually completing a circuit. This paradigm is further discussed below, Hydraulic ohms are the units of hydraulic impedance, which is defined as the ratio of pressure to volume flow rate. The pressure and volume flow variables are treated as phasors in this definition, a slightly different paradigm is used in acoustics, where acoustic impedance is defined as a relationship between pressure and air speed. In this paradigm, a cavity with a hole is analogous to a capacitor that stores compressional energy when the time-dependent pressure deviates from atmospheric pressure. A hole is analogous to an inductor that stores kinetic energy associated with the flow of air, electric potential In general, this is equivalent to hydraulic head. This model assumes that the water is flowing horizontally, so that the force of gravity can be ignored, in this case electric potential is equivalent to pressure. The voltage is a difference in pressure between two points, electric potential and voltage are usually measured in volts. Current Equivalent to a volume flow rate, that is. Electric charge Equivalent to a quantity of water, conducting wire A relatively wide pipe completely filled with water is equivalent to a piece of wire. When comparing to a piece of wire, the pipe should be thought of as having semi-permanent caps on the ends, connecting one end of a wire to a circuit is equivalent to un-capping one end of the pipe and attaching it to another pipe. With few exceptions, a wire with one end attached to a circuit will do nothing, the pipe remains capped on the free end. Resistor A constriction in the bore of the pipe which requires more pressure to pass the same amount of water, all pipes have some resistance to flow, just as all wires have some resistance to current
Hydraulic analogy
–
Node in
Kirchoff's junction rule: A
pipe tee filled with flowing water.
Hydraulic analogy
28.
Pressure
–
Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the relative to the ambient pressure. Various units are used to express pressure, Pressure may also be expressed in terms of standard atmospheric pressure, the atmosphere is equal to this pressure and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, Pressure is the amount of force acting per unit area. The symbol for it is p or P, the IUPAC recommendation for pressure is a lower-case p. However, upper-case P is widely used. The usage of P vs p depends upon the field in one is working, on the nearby presence of other symbols for quantities such as power and momentum. Mathematically, p = F A where, p is the pressure, F is the normal force and it relates the vector surface element with the normal force acting on it. It is incorrect to say the pressure is directed in such or such direction, the pressure, as a scalar, has no direction. The force given by the relationship to the quantity has a direction. If we change the orientation of the element, the direction of the normal force changes accordingly. Pressure is distributed to solid boundaries or across arbitrary sections of normal to these boundaries or sections at every point. It is a parameter in thermodynamics, and it is conjugate to volume. The SI unit for pressure is the pascal, equal to one newton per square metre and this name for the unit was added in 1971, before that, pressure in SI was expressed simply in newtons per square metre. Other units of pressure, such as pounds per square inch, the CGS unit of pressure is the barye, equal to 1 dyn·cm−2 or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre, but using the names kilogram, gram, kilogram-force, or gram-force as units of force is expressly forbidden in SI. The technical atmosphere is 1 kgf/cm2, since a system under pressure has potential to perform work on its surroundings, pressure is a measure of potential energy stored per unit volume. It is therefore related to density and may be expressed in units such as joules per cubic metre. Similar pressures are given in kilopascals in most other fields, where the prefix is rarely used
Pressure
–
Mercury column
Pressure
–
Pressure as exerted by particle collisions inside a closed container.
Pressure
–
The effects of an external pressure of 700bar on an aluminum cylinder with 5mm wall thickness
Pressure
–
low pressure chamber in
Bundesleistungszentrum Kienbaum, Germany
29.
Resistor
–
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of power as heat may be used as part of motor controls, in power distribution systems. Fixed resistors have resistances that only slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements, or as sensing devices for heat, light, humidity, force, Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds, Resistors are also implemented within integrated circuits. The electrical function of a resistor is specified by its resistance, the nominal value of the resistance falls within the manufacturing tolerance, indicated on the component. Two typical schematic diagram symbols are as follows, The notation to state a resistors value in a circuit diagram varies, one common scheme is the letter and digit code for resistance values following IEC60062. It avoids using a separator and replaces the decimal separator with a letter loosely associated with SI prefixes corresponding with the parts resistance. For example, 8K2 as part marking code, in a diagram or in a bill of materials indicates a resistor value of 8.2 kΩ. Additional zeros imply a tighter tolerance, for example 15M0 for three significant digits, when the value can be expressed without the need for a prefix, an R is used instead of the decimal separator. For example, 1R2 indicates 1.2 Ω, and 18R indicates 18 Ω, for example, if a 300 ohm resistor is attached across the terminals of a 12 volt battery, then a current of 12 /300 =0.04 amperes flows through that resistor. Practical resistors also have some inductance and capacitance which affect the relation between voltage and current in alternating current circuits, the ohm is the SI unit of electrical resistance, named after Georg Simon Ohm. An ohm is equivalent to a volt per ampere, since resistors are specified and manufactured over a very large range of values, the derived units of milliohm, kilohm, and megohm are also in common usage. The total resistance of resistors connected in series is the sum of their resistance values. R e q = R1 + R2 + ⋯ + R n, the total resistance of resistors connected in parallel is the reciprocal of the sum of the reciprocals of the individual resistors. 1 R e q =1 R1 +1 R2 + ⋯ +1 R n. For example, a 10 ohm resistor connected in parallel with a 5 ohm resistor, a resistor network that is a combination of parallel and series connections can be broken up into smaller parts that are either one or the other
Resistor
–
A typical axial-lead resistor
Resistor
–
Axial -lead resistors on tape. The component is cut from the tape during assembly and the part is inserted into the board.
Resistor
–
An aluminium-housed power resistor rated for 50 W when heat-sinked
Resistor
–
Resistors with wire leads for through-hole mounting
30.
Capacitor
–
A capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance, a capacitor was therefore historically first known as an electric condenser. The physical form and construction of practical capacitors vary widely and many types are in common use. Most capacitors contain at least two electrical conductors often in the form of plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, the nonconducting dielectric acts to increase the capacitors charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, a capacitor does not dissipate energy. No current actually flows through the dielectric, instead, the effect is a displacement of charges through the source circuit, if the condition is maintained sufficiently long, this displacement current through the battery ceases. However, if a voltage is applied across the leads of the capacitor. Capacitance is defined as the ratio of the charge on each conductor to the potential difference between them. The unit of capacitance in the International System of Units is the farad, capacitance values of typical capacitors for use in general electronics range from about 1 pF to about 1 mF. The capacitance of a capacitor is proportional to the area of the plates. In practice, the dielectric between the plates passes a small amount of leakage current and it has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance, Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies, in resonant circuits they tune radios to particular frequencies. In electric power systems, they stabilize voltage and power flow. The property of energy storage in capacitors was exploited as dynamic memory in digital computers. Von Kleists hand and the water acted as conductors, and the jar as a dielectric, von Kleist found that touching the wire resulted in a powerful spark, much more painful than that obtained from an electrostatic machine
Capacitor
–
Capacitor
Capacitor
–
Miniature low-voltage capacitors (next to a cm ruler)
Capacitor
–
A typical
electrolytic capacitor
Capacitor
–
4 electrolytic capacitors of different voltages and capacitance
31.
Inductor
–
An inductor, also called a coil or reactor, is a passive two-terminal electrical component that stores electrical energy in a magnetic field when electric current is flowing through it. An inductor typically consists of a conductor, such as a wire. When the current flowing through an inductor changes, the magnetic field induces a voltage in the conductor. According to Lenzs law, the direction of induced electromotive force opposes the change in current that created it, as a result, inductors oppose any changes in current through them. An inductor is characterized by its inductance, which is the ratio of the voltage to the rate of change of current, in the International System of Units, the unit of inductance is the henry. Inductors have values that range from 1 µH to 1 H. Many inductors have a core made of iron or ferrite inside the coil. Along with capacitors and resistors, inductors are one of the three passive linear circuit elements that make up electronic circuits, Inductors are widely used in alternating current electronic equipment, particularly in radio equipment. They are used to block AC while allowing DC to pass and they are also used in electronic filters to separate signals of different frequencies, and in combination with capacitors to make tuned circuits, used to tune radio and TV receivers. An electric current flowing through a conductor generates a magnetic field surrounding it, any changes of current and therefore in the magnetic flux through the cross-section of the inductor creates an opposing electromotive force in the conductor. An inductor is a component consisting of a wire or other conductor shaped to increase the flux through the circuit. Winding the wire into a coil increases the number of times the magnetic flux lines link the circuit, increasing the field, the more turns, the higher the inductance. The inductance also depends on the shape of the coil, separation of the turns, by adding a magnetic core made of a ferromagnetic material like iron inside the coil, the magnetizing field from the coil will induce magnetization in the material, increasing the magnetic flux. The high permeability of a core can increase the inductance of a coil by a factor of several thousand over what it would be without it. Any change in the current through an inductor creates a changing flux, for example, an inductor with an inductance of 1 henry produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second. This is usually taken to be the relation of the inductor. The dual of the inductor is the capacitor, which stores energy in a field rather than a magnetic field. Its current-voltage relation is obtained by exchanging current and voltage in the inductor equations, the polarity of the induced voltage is given by Lenzs law, which states that it will be such as to oppose the change in current
Inductor
–
A selection of low-value inductors
Inductor
–
Large 50
MVAR three-phase iron-core loading inductor at an Austrian utility substation
Inductor
–
A ferrite "bead" choke, consisting of an encircling ferrite cylinder, removes electronic noise from a computer power cord.
Inductor
–
A ferrite core inductor with two 47 mH windings.
32.
Resistors
–
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of power as heat may be used as part of motor controls, in power distribution systems. Fixed resistors have resistances that only slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements, or as sensing devices for heat, light, humidity, force, Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds, Resistors are also implemented within integrated circuits. The electrical function of a resistor is specified by its resistance, the nominal value of the resistance falls within the manufacturing tolerance, indicated on the component. Two typical schematic diagram symbols are as follows, The notation to state a resistors value in a circuit diagram varies, one common scheme is the letter and digit code for resistance values following IEC60062. It avoids using a separator and replaces the decimal separator with a letter loosely associated with SI prefixes corresponding with the parts resistance. For example, 8K2 as part marking code, in a diagram or in a bill of materials indicates a resistor value of 8.2 kΩ. Additional zeros imply a tighter tolerance, for example 15M0 for three significant digits, when the value can be expressed without the need for a prefix, an R is used instead of the decimal separator. For example, 1R2 indicates 1.2 Ω, and 18R indicates 18 Ω, for example, if a 300 ohm resistor is attached across the terminals of a 12 volt battery, then a current of 12 /300 =0.04 amperes flows through that resistor. Practical resistors also have some inductance and capacitance which affect the relation between voltage and current in alternating current circuits, the ohm is the SI unit of electrical resistance, named after Georg Simon Ohm. An ohm is equivalent to a volt per ampere, since resistors are specified and manufactured over a very large range of values, the derived units of milliohm, kilohm, and megohm are also in common usage. The total resistance of resistors connected in series is the sum of their resistance values. R e q = R1 + R2 + ⋯ + R n, the total resistance of resistors connected in parallel is the reciprocal of the sum of the reciprocals of the individual resistors. 1 R e q =1 R1 +1 R2 + ⋯ +1 R n. For example, a 10 ohm resistor connected in parallel with a 5 ohm resistor, a resistor network that is a combination of parallel and series connections can be broken up into smaller parts that are either one or the other
Resistors
–
A typical axial-lead resistor
Resistors
–
Axial -lead resistors on tape. The component is cut from the tape during assembly and the part is inserted into the board.
Resistors
–
An aluminium-housed power resistor rated for 50 W when heat-sinked
Resistors
–
Resistors with wire leads for through-hole mounting
33.
Flux
–
Flux is either of two separate simple and ubiquitous concepts throughout physics and applied mathematics. Within a discipline, the term is used consistently. Both concepts have mathematical rigor, enabling comparison of the underlying math when the terminology is unclear, for transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property. In electromagnetism, flux is a quantity, defined as the surface integral of the component of a vector field perpendicular to the surface at each point. As will be clear, the easiest way to relate the two concepts is that the surface integral of a flux according to the first definition is a flux according to the second definition. The word flux comes from Latin, fluxus means flow, as fluxion, this term was introduced into differential calculus by Isaac Newton. One could argue, based on the work of James Clerk Maxwell, the specific quote from Maxwell is, In the case of fluxes, we have to take the integral, over a surface, of the flux through every element of the surface. The result of operation is called the surface integral of the flux. It represents the quantity which passes through the surface, according to the first definition, flux may be a single vector, or flux may be a vector field / function of position. In the latter case flux can readily be integrated over a surface, by contrast, according to the second definition, flux is the integral over a surface, it makes no sense to integrate a second-definition flux for one would be integrating over a surface twice. Thus, Maxwells quote only makes sense if flux is being used according to the first definition and this is ironic because Maxwell was one of the major developers of what we now call electric flux and magnetic flux according to the second definition. This implies that Maxwell conceived as these fields as flows/fluxes of some sort, given a flux according to the second definition, the corresponding flux density, if that term is used, refers to its derivative along the surface that was integrated. By the Fundamental theorem of calculus, the flux density is a flux according to the first definition. Given a current such as electric current—charge per time, current density would also be a flux according to the first definition—charge per time per area. Concrete fluxes in the rest of this article will be used in accordance to their acceptance in the literature. In transport phenomena, flux is defined as the rate of flow of a property per unit area, the area is of the surface the property is flowing through or across. Here are 3 definitions in increasing order of complexity, each is a special case of the following. In all cases the frequent symbol j, is used for flux, q for the quantity that flows, t for time
Flux
34.
Multimeter
–
A multimeter or a multitester, also known as a VOM, is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance, analog multimeters use a microammeter with a moving pointer to display readings. Digital multimeters have a display, and may also show a graphical bar representing the measured value. Digital multimeters are now far more due to their cost and precision. A multimeter can be a device useful for basic fault finding and field service work. Multimeters are available in a range of features and prices. Cheap multimeters can cost less than US$10, while models with certified calibration can cost more than US$5,000. The first moving-pointer current-detecting device was the galvanometer in 1820 and these were used to measure resistance and voltage by using a Wheatstone bridge, and comparing the unknown quantity to a reference voltage or resistance. While useful in the lab, the devices were very slow and these galvanometers were bulky and delicate. The DArsonval/Weston meter movement uses a coil which carries a pointer. The coil rotates in a permanent magnetic field and is restrained by fine spiral springs which also serve to carry current into the moving coil and it gives proportional measurement rather than just detection, and deflection is independent of the orientation of the meter. Instead of balancing a bridge, values could be read off the instruments scale. The basic moving coil meter is only for direct current measurements. It is easily adapted to read heavier currents by using shunts or to voltage using series resistances known as multipliers. To read alternating currents or voltages, a rectifier is needed, multimeters were invented in the early 1920s as radio receivers and other vacuum tube electronic devices became more common. Macadie invented an instrument which could measure amperes, volts and ohms, the meter comprised a moving coil meter, voltage and precision resistors, and switches and sockets to select the range. The Automatic Coil Winder and Electrical Equipment Company was set up to manufacture the Avometer, although a shareholder of ACWEECO, Mr MacAdie continued to work for the Post Office until his retirement in 1933. His son, Hugh S. MacAdie, joined ACWEECO in 1927, Automatic Coil Winder and Electrical Equipment Company
Multimeter
–
An analog multimeter
Multimeter
–
A 4 1/2 digit digital multimeter, the Fluke 87-V
Multimeter
–
Multimeter test leads.
Multimeter
–
1920s Pocket Multimeter
35.
Electrochemical cell
–
An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or facilitating chemical reactions through the introduction of electrical energy. A common example of a cell is a standard 1.5 - volt cell meant for consumer use. This type of device is known as a galvanic cell. A battery consists of one or more cells, connected in parallel or series pattern. An electrochemical cell consists of two half-cells, each half-cell consists of an electrode and an electrolyte. The two half-cells may use the same electrolyte, or they may use different electrolytes, the chemical reactions in the cell may involve the electrolyte, the electrodes, or an external substance. In a full electrochemical cell, species from one half-cell lose electrons to their electrode while species from the other half-cell gain electrons from their electrode. A salt bridge is employed to provide ionic contact between two half-cells with different electrolytes, yet prevent the solutions from mixing and causing unwanted side reactions. An alternative to a bridge is to allow direct contact between the two half-cells, for example in simple electrolysis of water. As electrons flow from one half-cell to the other through an external circuit, if no ionic contact were provided, this charge difference would quickly prevent the further flow of electrons. A salt bridge allows the flow of negative or positive ions to maintain a charge distribution between the oxidation and reduction vessels, while keeping the contents otherwise separate. Other devices for achieving separation of solutions are porous pots and gelled solutions, a porous pot is used in the Bunsen cell. Each half-cell has a characteristic voltage, various choices of substances for each half-cell give different potential differences. Each reaction is undergoing an equilibrium reaction between different oxidation states of the ions, When equilibrium is reached, the cell cannot provide further voltage. In the half-cell that is undergoing oxidation, the closer the equilibrium lies to the ion/atom with the more positive oxidation state the potential this reaction will provide. Likewise, in the reaction, the closer the equilibrium lies to the ion/atom with the more negative oxidation state the higher the potential. The cell potential can be predicted through the use of electrode potentials and these half-cell potentials are defined relative to the assignment of 0 volts to the standard hydrogen electrode. The difference in voltage between electrode potentials gives a prediction for the potential measured, when calculating the difference in voltage, one must first rewrite the half-cell reaction equations to obtain a balanced oxidation-reduction equation
Electrochemical cell
–
The
Bunsen cell, invented by
Robert Bunsen.
Electrochemical cell
–
A demonstration electrochemical cell setup resembling the
Daniell cell. The two half-cells are linked by a salt bridge carrying ions between them. Electrons flow in the external circuit.
36.
Battery (electricity)
–
An electric battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights, smartphones, and electric cars. When a battery is supplying power, its positive terminal is the cathode. The terminal marked negative is the source of electrons that when connected to a circuit will flow. It is the movement of ions within the battery which allows current to flow out of the battery to perform work. Historically the term specifically referred to a device composed of multiple cells. Primary batteries are used once and discarded, the materials are irreversibly changed during discharge. Common examples are the battery used for flashlights and a multitude of portable electronic devices. Secondary batteries can be discharged and recharged multiple times using mains power from a wall socket, examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and smartphones. According to a 2005 estimate, the battery industry generates US$48 billion in sales each year. Batteries have much lower energy than common fuels such as gasoline. This is somewhat offset by the efficiency of electric motors in producing mechanical work. The usage of battery to describe a group of electrical devices dates to Benjamin Franklin, alessandro Volta built and described the first electrochemical battery, the voltaic pile, in 1800. This was a stack of copper and zinc plates, separated by brine-soaked paper disks, Volta did not understand that the voltage was due to chemical reactions. Although early batteries were of value for experimental purposes, in practice their voltages fluctuated. It consisted of a pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid. These wet cells used liquid electrolytes, which were prone to leakage and spillage if not handled correctly, many used glass jars to hold their components, which made them fragile and potentially dangerous. These characteristics made wet cells unsuitable for portable appliances, near the end of the nineteenth century, the invention of dry cell batteries, which replaced the liquid electrolyte with a paste, made portable electrical devices practical. Batteries convert chemical energy directly to electrical energy, a battery consists of some number of voltaic cells
Battery (electricity)
–
Various cells and batteries (top-left to bottom-right): two
AA, one
D, one handheld
ham radio battery, two
9-volt (PP3), two
AAA, one
C, one
camcorder battery, one
cordless phone battery.
Battery (electricity)
–
A
voltaic pile, the first battery
Battery (electricity)
–
From top to bottom: a large 4.5-volt (3R12) battery, a
D Cell, a
C cell, an
AA cell, an
AAA cell, an
AAAA cell, an
A23 battery, a 9-volt
PP3 battery, and a pair of
button cells (CR2032 and LR44).
Battery (electricity)
–
A device to check battery voltage
37.
Galvanic cell
–
It generally consists of two different metals connected by a salt bridge, or individual half-cells separated by a porous membrane. Volta was the inventor of the pile, the first electrical battery. In common usage, the battery has come to include a single galvanic cell. In 1780, Luigi Galvani discovered that two different metals are connected and then both touched at the same time to two different parts of a nerve of a frog leg, then the leg contracts. The voltaic pile, invented by Alessandro Volta in the 1800s, however, Volta built it entirely out of non-biological material in order to challenge Galvanis animal electricity theory in favour of his own metal-metal contact electricity theory. Carlo Matteucci in his turn constructed a battery out of biological material in answer to Volta. These discoveries paved the way for electrical batteries, Voltas cell was named an IEEE Milestone in 1999 and it was suggested by Wilhelm König in 1940 that the object known as the Baghdad battery might represent galvanic cell technology from ancient Parthia. Replicas filled with acid or grape juice have been shown to produce a voltage. However, it is far from certain that this was its purpose—other scholars have pointed out that it is similar to vessels known to have been used for storing parchment scrolls. In its simplest form, a half-cell consists of a metal that is submerged in a solution. This reduction reaction causes the electrons throughout the metal-B electrode, the wire. By definition, The anode is the electrode where oxidation takes place, in a cell, it is the negative electrode, as when oxidation occurs. These electrons then migrate to the cathode, however, in electrolysis, an electric current stimulates electron flow in the opposite direction. Thus, the anode is positive, and the statement anode attracts anions is true, the metal-A electrode is the anode. Instead, there is a tendency for aqueous ions to be reduced by the incoming electrons from the anode. However, in electrolysis, the cathode is the negative terminal, in this situation, the statement the cathode attracts cations is true. The metal-B electrode is the cathode, copper readily oxidizes zinc, for the Daniell cell depicted in the figure, the anode is zinc and the cathode is copper, and the anions in the solutions are sulfates of the respective metals. When an electrically conducting device connects the electrodes, the reaction is, Zn + Cu2+ → Zn2++ Cu The zinc electrode is dissolved
Galvanic cell
–
Contents
38.
Resting potential
–
Apart from the latter two, which occur in excitable cells, membrane voltage in the majority of non-excitable cells can also undergo changes in response to environmental or intracellular stimuli. Conventionally, resting membrane potential can be defined as a stable, ground value of transmembrane voltage in animal. Any voltage is a difference in potential between two points—for example, the separation of positive and negative electric charges on opposite sides of a resistive barrier. The typical resting membrane potential of a cell arises from the separation of ions from intracellular. Again, because of the relative permeability for potassium, the resulting membrane potential is almost always close to the potassium reversal potential. But in order for this process to occur, a gradient of potassium ions must first be set up. This work is done by the ion pumps/transporters and/or exchangers and generally is powered by ATP, in other cases, for example, a membrane potential may be established by acidification of the inside of a membranous compartment. Cell membranes are permeable to only a subset of ions. These usually include potassium ions, chloride ions, bicarbonate ions, to simplify the description of the ionic basis of the resting membrane potential, it is most useful to consider only one ionic species at first, and consider the others later. Since trans-plasma-membrane potentials are almost always determined primarily by potassium permeability, Panel 1 of the diagram shows a diagrammatic representation of a simple cell where a concentration gradient has already been established. This panel is drawn as if the membrane has no permeability to any ion, there is no membrane potential, because despite there being a concentration gradient for potassium, there is no net charge imbalance across the membrane. There would be net movement from the side of the membrane with a concentration of the ion to the side with lower concentration. Such a movement of one ion across the membrane would result in a net imbalance of charge across the membrane and this is a common mechanism by which many cells establish a membrane potential. In panel 2 of the diagram, the membrane has been made permeable to potassium ions. These anions are mostly contributed by protein, there is energy stored in the potassium ion concentration gradient that can be converted into an electrical gradient when potassium ions move out of the cell. An internal K+ is simply more likely to leave the cell than an extracellular K+ is to enter it and it is a matter of simple diffusion doing work by dissipating the concentration gradient. As potassium leaves the cell, it is leaving behind the anions, therefore, a charge separation is developing as K+ leaves the cell. This charge separation creates a transmembrane voltage and this transmembrane voltage is the membrane potential
Resting potential
Resting potential
–
The
Na+
/K+
-ATPase, as well as effects of diffusion of the involved ions, are major mechanisms to maintain the resting potential across the membranes of animal cells.
39.
Nickel metal hydride battery
–
A nickel–metal hydride battery, abbreviated NiMH or Ni–MH, is a type of rechargeable battery. The chemical reaction at the electrode is similar to that of the nickel–cadmium cell. However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium, a NiMH battery can have two to three times the capacity of an equivalent size NiCd, and its energy density can approach that of a lithium-ion battery. Work on NiMH batteries began at the Battelle-Geneva Research Center following the invention in 1967. It was based on sintered Ti2Ni+TiNi+x alloys and NiOOH-electrodes, development was sponsored over nearly two decades by Daimler-Benz and by Volkswagen AG within Deutsche Automobilgesellschaft, now a subsidiary of Daimler AG. The batteries specific energy reached 50 W·h/kg, power density up to 1000 W/kg, patent applications were filed in European countries, the United States, and Japan. Interest grew in the 1970s with the commercialisation of the battery for satellite applications. Hydride technology promised an alternative, less bulky way to store the hydrogen, Research carried out by Philips Laboratories and Frances CNRS developed new high-energy hybrid alloys incorporating rare earth metals for the negative electrode. However, these suffered from instability in alkaline electrolyte and consequently insufficient cycle life. In 1987, Willems and Buschow demonstrated a successful battery based on this approach which kept 84% of its capacity after 4000 charge–discharge cycles. More economically viable alloys using mischmetal instead of lanthanum were soon developed, modern NiMH cells were based on this design. The first consumer grade NiMH cells became commercially available in 1989, in 1998, Ovonic Battery Co. improved the Ti–Ni alloy structure and composition and patented its innovations. In 2008, more than two million cars worldwide were manufactured with NiMH batteries. In the European Union and due to its Battery Directive, nickel–metal hydride batteries replaced Ni–Cd batteries for portable consumer use, about 22% of portable rechargeable batteries sold in Japan in 2010 were NiMH. In Switzerland in 2009, the equivalent statistic was approximately 60% and this percentage has fallen over time due to the increase in manufacture of lithium-ion batteries, in 2000, almost half of all portable rechargeable batteries sold in Japan were NiMH. The negative electrode reaction occurring in a NiMH cell is, H2O + M + e− ⇌ OH− + MH The charge reaction is read left-to-right and the discharge reaction is read right-to-left. On the positive electrode, nickel oxyhydroxide, NiO, is formed, many different compounds have been developed for this application, but those in current use fall into two classes. The most common is AB5, where A is a rare mixture of lanthanum, cerium, neodymium, praseodymium and B is nickel, cobalt, manganese
Nickel metal hydride battery
–
Modern NiMH rechargeable cells
Nickel metal hydride battery
–
Positive terminal
Nickel metal hydride battery
–
NiMH cell that popped its cap due to failed safety valve
Nickel metal hydride battery
–
High power Ni–MH battery of
Toyota NHW20 Prius,
Japan
40.
Nickel-cadmium battery
–
The nickel–cadmium battery is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. Wet-cell nickel-cadmium batteries were invented in 1899, among rechargeable battery technologies, NiCd rapidly lost market share in the 1990s, to NiMH and Li-ion batteries, market share dropped by 80%. A NiCd battery has a terminal voltage during discharge of around 1.2 volts which decreases little until nearly the end of discharge, however, the materials are more costly than that of the lead acid battery, and the cells have high self-discharge rates. Sealed NiCd cells were at one time used in portable power tools, photography equipment, flashlights, emergency lighting, hobby R/C. The superior capacity of the Nickel-metal hydride batteries, and more recently their lower cost, has largely supplanted their use, further, the environmental impact of the disposal of the toxic metal cadmium has contributed considerably to the reduction in their use. Within the European Union, NiCd batteries can now only be supplied for replacement purposes or for certain types of new equipment such as medical devices, larger ventilated wet cell NiCd batteries are used in emergency lighting, standby power, and uninterruptible power supplies and other applications. The first Ni–Cd battery was created by Waldemar Jungner of Sweden in 1899, at that time, the only direct competitor was the lead–acid battery, which was less physically and chemically robust. With minor improvements to the first prototypes, energy density increased to about half of that of primary batteries. Jungner experimented with substituting iron for the cadmium in varying quantities, jungners work was largely unknown in the United States. Thomas Edison patented a nickel– or cobalt–cadmium battery in 1902, in 1906, Jungner established a factory close to Oskarshamn, Sweden to produce flooded design Ni–Cd batteries. In 1932 active materials were deposited inside a porous nickel-plated electrode, the first production in the United States began in 1946. Up to this point, the batteries were pocket type, constructed of nickel-plated steel pockets containing nickel, around the middle of the twentieth century, sintered-plate Ni–Cd batteries became increasingly popular. Fusing nickel powder at a well below its melting point using high pressures creates sintered plates. The plates thus formed are highly porous, about 80 percent by volume, positive and negative plates are produced by soaking the nickel plates in nickel- and cadmium-active materials, respectively. Sintered plates are much thinner than the pocket type, resulting in greater surface area per volume. In general, the amount of reactive material surface area in a battery. Today, all consumer Ni–Cd batteries use the Swiss roll or jelly-roll configuration and this design incorporates several layers of positive and negative material rolled into a cylindrical shape. This design reduces internal resistance as there is an amount of electrode in contact with the active material in each cell
Nickel-cadmium battery
–
From top to bottom: "Gumstick", AA, and AAA Ni–Cd batteries
Nickel-cadmium battery
–
View of a vented cell aircraft battery from the side
Nickel-cadmium battery
–
Eight Ni-Cd batteries in a battery pack
41.
Alkaline battery
–
Alkaline batteries are a type of primary battery dependent upon the reaction between zinc and manganese dioxide. Another type of batteries are secondary rechargeable alkaline battery, which allows reuse of specially designed cells. Compared with zinc-carbon batteries of the Leclanché or zinc chloride types, alkaline batteries have an energy density and longer shelf-life. The alkaline battery gets its name because it has an electrolyte of potassium hydroxide. Other battery systems also use alkaline electrolytes, but they use different active materials for the electrodes, Alkaline batteries account for 80% of manufactured batteries in the US and over 10 billion individual units produced worldwide. In Japan alkaline batteries account for 46% of all battery sales. In Switzerland alkaline batteries account for 68%, in the UK 60%, Alkaline batteries are used in many household items such as MP3 players, CD players, digital cameras, pagers, toys, lights, and radios, to name a few. Batteries with alkaline electrolyte were first developed by Waldemar Jungner in 1899, on October 9,1957, Urry, Karl Kordesch, and P. A. Marsal filed US patent for the alkaline battery and it was granted in 1960 and was assigned to the Union Carbide Corporation. When introduced in the late 1960s, alkaline batteries contained a small amount of mercury amalgam to control side reactions at the zinc anode. With mercury content reduced by law and improvements in the purity and consistency of materials, in an alkaline battery, the negative electrode is zinc and the positive electrode is manganese dioxide. The alkaline electrolyte of potassium hydroxide is not part of the reaction, only the zinc, the alkaline electrolyte of potassium hydroxide remains, as there are equal amounts of OH− consumed and produced. An alkaline cell can provide three and five times capacity. The capacity of a battery is strongly dependent on the load. An AA-sized alkaline battery might have a capacity of 3000 mAh at low drain, but at a load of 1 ampere, which is common for digital cameras. The voltage of the battery declines steadily during use, so the usable capacity depends on the cut-off voltage of the application. Unlike Leclanche cells, the alkaline cell delivers about as much capacity on intermittent or continuous light loads, on a heavy load, capacity is reduced on continuous discharge compared with intermittent discharge, but the reduction is less than for Leclanche cells. The nominal voltage of an alkaline cell as established by manufacturer standards is 1.5 V
Alkaline battery
–
From left to right: C, AA, AAA, N, and 9V alkaline batteries
Alkaline battery
–
Nickel-iron batteries manufactured between 1972 and 1975 under the "
Exide " brand, originally developed in 1901 by Thomas Edison.
Alkaline battery
–
Leaked alkaline battery
42.
Zinc-carbon battery
–
It is usually conveniently packaged in a zinc can which also serves as the anode with a negative potential, while the inert carbon rod is the positive cathode. General purpose batteries may use a paste of ammonium chloride as electrolyte. Heavy duty types use a primarily composed of zinc chloride. Zinc–carbon batteries were the first commercial dry batteries, developed from the technology of the wet Leclanché cell and they made flashlights and other portable devices possible, because the battery can function in any orientation. They are still useful in low drain or intermittent use devices such as controls, flashlights. Zinc–carbon dry cells are primary cells. By 1876, the wet Leclanché cell was made with a block of manganese dioxide. In 1886 Carl Gassner patented a dry version by using a cup as the anode and making the electrolyte with a paste of plaster of Paris to gel. In 1898 Conrad Hubert used consumer batteries manufactured by W. H. Lawrence to power what was the first flashlight, in 1900 Gassner demonstrated dry cells for portable lighting at the Worlds Fair in Paris. Improvements include the use of purer grades of manganese dioxide, better sealing, zinc chloride cells use a paste primarily composed of zinc chloride, which gives a longer life and steadier voltage output compared with ammonium chloride electrolyte. Manufacturers must now use more highly purified zinc to prevent local action, as of 2011 zinc-carbon batteries accounted for 20% of all portable batteries in the UK, and 18% in the EU. In Japan they account for 6% of primary battery sales, also in 2016 researchers discovered that Zn-Mn cells were subject to a chemical reaction. The anode was reversibly reacting with protons from the electrolyte to create zinc hydroxyl sulfate that coated the electrode. Battery costs were expected to be comparable to the cells used in autos. The container of the dry cell is a zinc can. Carbon is the only practical conductor material because every common metal quickly corrodes in the electrode in salt based electrolyte. Early types, and low-cost cells, use a separator consisting of a layer of starch or flour, a layer of starch-coated paper is used in modern cells, which is thinner and allows more manganese dioxide to be used. Originally cells were sealed with a layer of asphalt to prevent drying out of the electrolyte, the carbon rod is slightly porous, which allows accumulated gas to escape while retaining the aqueous electrolyte
Zinc-carbon battery
–
Old 3V zinc–carbon battery, ca. 1960, with cardboard casing.
Zinc-carbon battery
–
Zinc–carbon batteries of various sizes.
Zinc-carbon battery
–
Progressive corrosion of zinc–carbon batteries.
Zinc-carbon battery
–
Disassembled zinc chloride cell (similar to zinc carbon cell). 1:entire cell, 2:steel casing, 3:zinc negative electrode, 4:carbon rod, 5:positive electrode (Manganese dioxide mixed with carbon powder and electrolyte), 6:paper separator, 7:polyethylene leak proof isolation, 8:sealing rings, 9-negative terminal, 10-positive terminal (originally connected to carbon rod)
43.
Lithium iron phosphate battery
–
The lithium iron phosphate battery, also called LFP battery, is a type of rechargeable battery, specifically a lithium-ion battery, which uses LiFePO4 as a cathode material. LiFePO4 is finding a number of roles in vehicle use, LiFePO4 is a natural mineral of the olivine family. Its use as an electrode which was first described in published literature by John B. Goodenoughs research group at the University of Texas in 1996, as a material for rechargeable lithium batteries. Its key barrier to commercialization was intrinsically low electrical conductivity and this problem was overcome by reducing the particle size, coating the LiFePO4 particles with conductive materials such as carbon, or both. This approach was developed by Michel Armand and his coworkers, another approach by Yet Ming Chiangs group consisted of doping LFP with cations of materials such as aluminium, niobium, and zirconium. Products are now in production and are used in industrial products by major corporations including Black and Deckers DeWalt brand. MIT introduced a new coating that allows the ions to move easily within the battery. The Beltway Battery utilizes a system that allows the lithium ions to enter. The scientists discovered that by coating lithium iron phosphate particles in a material called lithium pyrophosphate, ions bypass the channels. Rechargeable batteries store and discharge energy as charged atoms form between two electrodes, the anode and cathode and their charge and discharge rate are restricted by the speed with which these ions move. Such technology could reduce the weight and size of the batteries, a small prototype battery cell has been developed that can fully charge in 10 to 20 seconds, compared with six minutes for standard battery cells. The LiFePO4 battery uses a lithium-ion-derived chemistry and shares many advantages and disadvantages with other Lithium-ion battery chemistries, LFP chemistry offers a longer cycle life than other lithium-ion approaches. Like nickel-based rechargeable batteries, LiFePO4 batteries have a constant discharge voltage. Voltage stays close to 3.2 V during discharge until the cell is exhausted and this allows the cell to deliver virtually full power until it is discharged. And it can greatly simplify or even eliminate the need for voltage regulation circuitry, because of the nominal 3.2 V output, four cells can be placed in series for a nominal voltage of 12.8 V. This comes close to the voltage of six-cell lead-acid batteries. LiFePO4 has higher current or peak-power ratings than LiCoO2, the energy density of a new LFP battery is some 14% lower than that of a new LiCoO2 battery
Lithium iron phosphate battery
–
Types
44.
Cobalt
–
Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt is found in the Earths crust only in chemically combined form, the free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal. In 1735, such ores were found to be reducible to a new metal, today, some cobalt is produced specifically from various metallic-lustered ores, for example cobaltite, but the main source of the element is as a by-product of copper and nickel mining. The copper belt in the Democratic Republic of the Congo, Central African Republic, cobalt is primarily used in the preparation of magnetic, wear-resistant and high-strength alloys. The compounds, cobalt silicate and cobalt aluminate give a deep blue color to glass, ceramics, inks, paints. Cobalt occurs naturally as only one isotope, cobalt-59. Cobalt-60 is an important radioisotope, used as a radioactive tracer. Cobalt is the center of coenzymes called cobalamins, the most common example of which is vitamin B12. As such, it is a trace dietary mineral for all animals. Cobalt in inorganic form is also a micronutrient for bacteria, algae, cobalt is a ferromagnetic metal with a specific gravity of 8.9. The Curie temperature is 1,115 °C and the moment is 1. 6–1.7 Bohr magnetons per atom. Cobalt has a relative permeability two-thirds that of iron, metallic cobalt occurs as two crystallographic structures, hcp and fcc. The ideal transition temperature between the hcp and fcc structures is 450 °C, but in practice, the difference is so small that random intergrowth of the two is common. Cobalt is a weakly reducing metal that is protected from oxidation by an oxide film. It is attacked by halogens and sulfur, heating in oxygen produces Co3O4 which loses oxygen at 900 °C to give the monoxide CoO. The metal reacts with fluorine at 520 K to give CoF3, with chlorine, bromine and iodine and it does not react with hydrogen gas or nitrogen gas even when heated, but it does react with boron, carbon, phosphorus, arsenic and sulfur. At ordinary temperatures, it reacts slowly with mineral acids, and very slowly with moist, common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +5 are also known. A common oxidation state for simple compounds is +2 and these salts form the pink-colored metal aquo complex 2+ in water
Cobalt
–
electrolytically refined cobalt chips
Cobalt
–
A block of
electrolytically refined cobalt (99.9% purity) cut from a large plate
Cobalt
–
Cobalt(II) chloride hexahydrate
Cobalt
–
Early Chinese blue and white porcelain, manufactured circa 1335
45.
Lithium polymer
–
A lithium polymer battery, or more correctly lithium-ion polymer battery, is a rechargeable battery of lithium-ion technology using a polymer electrolyte instead of the more common liquid electrolyte. High conductivity semisolid polymers form the electrolyte for LiPo cells are being used in tablet computers, after that, other packaging forms evolved, including the pouch format now also called LiPo. Lithium polymer cells have evolved from lithium-ion and lithium-metal batteries. The primary difference is instead of using a lithium-salt electrolyte held in an organic solvent. The solid electrolyte can be classified as one of three types, dry SPE, gelled SPE and porous SPE. The dry SPE was the first used in batteries, around 1978 by Michel Armand, Domain University, and 1985 by ANVAR and Elf Aquitaine of France. From 1990 several organisations like Mead and Valence in the United States, in 1996, Bellcore in the United States announced a rechargeable lithium polymer cell using porous SPE. A typical cell has four components, positive electrode, negative electrode, separator. The separator itself may be a polymer, such as a film of polyethylene or polypropylene, thus, even when the cell has a liquid electrolyte. In addition to this, the electrode can be further decomposed in three parts, the lithium-transition-metal-oxide, a conductive additive, and a polymer binder of poly. The negative electrode material may have the three parts, only with carbon replacing the lithium-metal-oxide. To prevent the electrodes from touching each other directly, a separator is in between which allows only the ions and not the electrode particles to migrate from one side to the other. For LiPo battery packs with cells connected in series, a specialised charger may monitor the charge on a per-cell basis so that all cells are brought to the state of charge. Unlike lithium-ion cylindrical and prismatic cells, which have a metal case, LiPo cells have a flexible, foil-type case. By themselves the cells are over 20% lighter than equivalent cylindrical cells of the same capacity, being lightweight is an advantage when the application requires minimum weight, such as in the case of radio controlled models. LiPo cells provide manufacturers with compelling advantages and they can easily produce batteries of almost any desired shape. For example, the space and weight requirements of mobile phones, also, they have low-self discharge rate, which is about 5% per month. Test reports warn of the risk of fire when the batteries are not used in accordance with the instructions, as of mid 2016, LiPo packs of 1.3 Ah exist, providing 95C continuous discharge, and short-time 190C bursts
Lithium polymer
–
A lithium-ion polymer battery used to power a mobile phone
Lithium polymer
–
An experimental lithium-ion polymer battery made by Lockheed-Martin for NASA
Lithium polymer
–
3-Cell LiPo battery for
RC-models
Lithium polymer
–
Apple
iPhone 3GS 's Lithium-ion polymer battery, which has expanded due to a short circuit failure.
46.
Transistor-transistor logic
–
Transistor–transistor logic is a class of digital circuits built from bipolar junction transistors and resistors. It is called transistor–transistor logic because transistors perform both the function and the amplifying function. TTL integrated circuits were used in applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics. After their introduction in integrated circuit form in 1963 by Sylvania, the 7400 series by Texas Instruments became particularly popular. TTL manufacturers offered a range of logic gate, flip-flops, counters. Several variations of the original TTL circuit design were developed, the variations offered interchangeable functions that had higher speed or lower power dissipation to allow design optimization. TTL devices were made in ceramic and plastic dual-in-line packages. TTL chips are now made in surface-mount packages. TTL became the foundation of computers and other digital electronics, TTL was invented in 1961 by James L. Buie of TRW, which declared it, particularly suited to the newly developing integrated circuit design technology. The original name for TTL was transistor-coupled transistor logic, the first commercial integrated-circuit TTL devices were manufactured by Sylvania in 1963, called the Sylvania Universal High-Level Logic family. The Sylvania parts were used in the controls of the Phoenix missile, the Texas Instruments 7400 family became an industry standard. Compatible parts were made by Motorola, AMD, Fairchild, Intel, Intersil, Signetics, Mullard, Siemens, SGS-Thomson, Rifa, National Semiconductor, not only did others make compatible TTL parts, but compatible parts were made using many other circuit technologies as well. At least one manufacturer, IBM, produced non-compatible TTL circuits for its own use, IBM used the technology in the IBM System/38, IBM4300, and IBM3081. The term TTL is applied to many generations of bipolar logic, with gradual improvements in speed. The most recently introduced family 74Fxx is still today, and was widely used into the late 90s. 74AS/ALS Advanced Schottky was introduced in 1985, as of 2008, Texas Instruments continues to supply the more general-purpose chips in numerous obsolete technology families, albeit at increased prices. Typically, TTL chips integrate no more than a few hundred transistors each, functions within a single package generally range from a few logic gates to a microprocessor bit-slice. TTL also became important because its low cost made digital techniques economically practical for tasks previously done by analog methods, the Kenbak-1, ancestor of the first personal computers, used TTL for its CPU instead of a microprocessor chip, which was not available in 1971
Transistor-transistor logic
–
A
Motorola 68000 -based computer with various TTL chips mounted on
breadboards.
Transistor-transistor logic
–
A real-time clock built of TTL chips around 1979.
47.
CMOS
–
Complementary metal–oxide–semiconductor, abbreviated as CMOS /ˈsiːmɒs/, is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, CMOS technology is also used for several analog circuits such as image sensors, data converters, and highly integrated transceivers for many types of communication. In 1963, while working for Fairchild Semiconductor, Frank Wanlass patented CMOS, CMOS is also sometimes referred to as complementary-symmetry metal–oxide–semiconductor. Two important characteristics of CMOS devices are high noise immunity and low power consumption. Since one transistor of the pair is always off, the series combination draws significant power only momentarily during switching between on and off states, CMOS also allows a high density of logic functions on a chip. It was primarily for this reason that CMOS became the most used technology to be implemented in VLSI chips, aluminium was once used but now the material is polysilicon. Other metal gates have made a comeback with the advent of high-k dielectric materials in the CMOS process, as announced by IBM and Intel for the 45 nanometer node and beyond. CMOS refers to both a style of digital circuitry design and the family of processes used to implement that circuitry on integrated circuits. CMOS circuitry dissipates less power than logic families with resistive loads, since this advantage has increased and grown more important, CMOS processes and variants have come to dominate, thus the vast majority of modern integrated circuit manufacturing is on CMOS processes. As of 2010, CPUs with the best performance per watt each year have been CMOS static logic since 1976, CMOS circuits use a combination of p-type and n-type metal–oxide–semiconductor field-effect transistor to implement logic gates and other digital circuits. CMOS always uses all enhancement-mode MOSFETs, CMOS circuits are constructed in such a way that all PMOS transistors must have either an input from the voltage source or from another PMOS transistor. Similarly, all NMOS transistors must have either an input from ground or from another NMOS transistor, the composition of a PMOS transistor creates low resistance between its source and drain contacts when a low gate voltage is applied and high resistance when a high gate voltage is applied. On the other hand, the composition of an NMOS transistor creates high resistance between source and drain when a low voltage is applied and low resistance when a high gate voltage is applied. CMOS accomplishes current reduction by complementing every nMOSFET with a pMOSFET, a high voltage on the gates will cause the nMOSFET to conduct and the pMOSFET to not conduct, while a low voltage on the gates causes the reverse. This arrangement greatly reduces power consumption and heat generation, however, during the switching time, both MOSFETs conduct briefly as the gate voltage goes from one state to another. This induces a brief spike in consumption and becomes a serious issue at high frequencies. The image on the right shows what happens when an input is connected to both a PMOS transistor and an NMOS transistor, when the voltage of input A is low, the NMOS transistors channel is in a high resistance state. This limits the current that can flow from Q to ground, the PMOS transistors channel is in a low resistance state and much more current can flow from the supply to the output
CMOS
–
CMOS inverter (
NOT logic gate)
48.
USB
–
It is currently developed by the USB Implementers Forum. USB was designed to standardize the connection of peripherals to personal computers. It has become commonplace on other devices, such as smartphones, PDAs, USB has effectively replaced a variety of earlier interfaces, such as serial ports and parallel ports, as well as separate power chargers for portable devices. Also, there are 5 modes of USB data transfer, in order of increasing bandwidth, Low Speed, Full Speed, High Speed, SuperSpeed, USB devices have some choice of implemented modes, and USB version is not a reliable statement of implemented modes. Modes are identified by their names and icons, and the specifications suggests that plugs, unlike other data buses, USB connections are directed, with both upstream and downstream ports emanating from a single host. This applies to power, with only downstream facing ports providing power. Thus, USB cables have different ends, A and B, therefore, in general, each different format requires four different connectors, a plug and receptacle for each of the A and B ends. USB cables have the plugs, and the corresponding receptacles are on the computers or electronic devices, in common practice, the A end is usually the standard format, and the B side varies over standard, mini, and micro. The mini and micro formats also provide for USB On-The-Go with a hermaphroditic AB receptacle, the micro format is the most durable from the point of view of designed insertion lifetime. The standard and mini connectors have a lifetime of 1,500 insertion-removal cycles. Likewise, the component of the retention mechanism, parts that provide required gripping force, were also moved into plugs on the cable side. A group of seven companies began the development of USB in 1994, Compaq, DEC, IBM, Intel, Microsoft, NEC, a team including Ajay Bhatt worked on the standard at Intel, the first integrated circuits supporting USB were produced by Intel in 1995. The original USB1.0 specification, which was introduced in January 1996, Microsoft Windows 95, OSR2.1 provided OEM support for the devices. The first widely used version of USB was 1.1, the 12 Mbit/s data rate was intended for higher-speed devices such as disk drives, and the lower 1.5 Mbit/s rate for low data rate devices such as joysticks. Apple Inc. s iMac was the first mainstream product with USB, following Apples design decision to remove all legacy ports from the iMac, many PC manufacturers began building legacy-free PCs, which led to the broader PC market using USB as a standard. The USB2.0 specification was released in April 2000 and was ratified by the USB Implementers Forum at the end of 2001.1 specification, the USB3.0 specification was published on 12 November 2008. Its main goals were to increase the transfer rate, decrease power consumption, increase power output. USB3.0 includes a new, higher speed bus called SuperSpeed in parallel with the USB2.0 bus, for this reason, the new version is also called SuperSpeed
USB
–
USB logo on the head of a standard-A plug, the most common
USB plug
USB
–
Universal Serial Bus (USB)
USB
–
A USB 2.0
PCI expansion card
USB
–
Two USB 3.0 standard-A sockets (left) and two USB 2.0 sockets (right) on a computer's front panel
