A magnetic field is a vector field that describes the magnetic influence of electric charges in relative motion and magnetized materials. Magnetic fields are observed from subatomic particles to galaxies. In everyday life, the effects of magnetic fields are seen in permanent magnets, which pull on magnetic materials and attract or repel other magnets. Magnetic fields surround and are created by magnetized material and by moving electric charges such as those used in electromagnets. Magnetic fields exert forces on nearby moving electrical torques on nearby magnets. In addition, a magnetic field that varies with location exerts a force on magnetic materials. Both the strength and direction of a magnetic field vary with location; as such, it is an example of a vector field. The term'magnetic field' is used for two distinct but related fields denoted by the symbols B and H. In the International System of Units, H, magnetic field strength, is measured in the SI base units of ampere per meter. B, magnetic flux density, is measured in tesla, equivalent to newton per meter per ampere.
H and B differ in. In a vacuum, B and H are the same aside from units. Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. Magnetic fields and electric fields are interrelated, are both components of the electromagnetic force, one of the four fundamental forces of nature. Magnetic fields are used throughout modern technology in electrical engineering and electromechanics. Rotating magnetic fields are used in both electric generators; the interaction of magnetic fields in electric devices such as transformers is studied in the discipline of magnetic circuits. Magnetic forces give information about the charge carriers in a material through the Hall effect; the Earth produces its own magnetic field, which shields the Earth's ozone layer from the solar wind and is important in navigation using a compass. Although magnets and magnetism were studied much earlier, the research of magnetic fields began in 1269 when French scholar Petrus Peregrinus de Maricourt mapped out the magnetic field on the surface of a spherical magnet using iron needles.
Noting that the resulting field lines crossed at two points he named those points'poles' in analogy to Earth's poles. He clearly articulated the principle that magnets always have both a north and south pole, no matter how finely one slices them. Three centuries William Gilbert of Colchester replicated Petrus Peregrinus' work and was the first to state explicitly that Earth is a magnet. Published in 1600, Gilbert's work, De Magnete, helped to establish magnetism as a science. In 1750, John Michell stated that magnetic poles attract and repel in accordance with an inverse square law. Charles-Augustin de Coulomb experimentally verified this in 1785 and stated explicitly that the north and south poles cannot be separated. Building on this force between poles, Siméon Denis Poisson created the first successful model of the magnetic field, which he presented in 1824. In this model, a magnetic H-field is produced by'magnetic poles' and magnetism is due to small pairs of north/south magnetic poles. Three discoveries in 1820 challenged this foundation of magnetism, though.
Hans Christian Ørsted demonstrated that a current-carrying wire is surrounded by a circular magnetic field. André-Marie Ampère showed that parallel wires with currents attract one another if the currents are in the same direction and repel if they are in opposite directions. Jean-Baptiste Biot and Félix Savart announced empirical results about the forces that a current-carrying long, straight wire exerted on a small magnet, determining that the forces were inversely proportional to the perpendicular distance from the wire to the magnet. Laplace deduced, but did not publish, a law of force based on the differential action of a differential section of the wire, which became known as the Biot–Savart law. Extending these experiments, Ampère published his own successful model of magnetism in 1825. In it, he showed the equivalence of electrical currents to magnets and proposed that magnetism is due to perpetually flowing loops of current instead of the dipoles of magnetic charge in Poisson's model.
This has the additional benefit of explaining. Further, Ampère derived both Ampère's force law describing the force between two currents and Ampère's law, like the Biot–Savart law described the magnetic field generated by a steady current. In this work, Ampère introduced the term electrodynamics to describe the relationship between electricity and magnetism. In 1831, Michael Faraday discovered electromagnetic induction when he found that a changing magnetic field generates an encircling electric field, he described this phenomenon in. Franz Ernst Neumann proved that, for a moving conductor in a magnetic field, induction is a consequence of Ampère's force law. In the process, he introduced the magnetic vector potential, shown to be equivalent to the underlying mechanism proposed by Faraday. In 1850, Lord Kelvin known as William Thomson, distinguished between two magnetic fields now denoted H and B; the former applied to the latter to Ampère's model and induction. Further, he derived how H and B relate to each other
A complex number is a number that can be expressed in the form a + bi, where a and b are real numbers, i is a solution of the equation x2 = −1. Because no real number satisfies this equation, i is called an imaginary number. For the complex number a + bi, a is called the real part, b is called the imaginary part. Despite the historical nomenclature "imaginary", complex numbers are regarded in the mathematical sciences as just as "real" as the real numbers, are fundamental in many aspects of the scientific description of the natural world. Complex numbers allow solutions to certain equations. For example, the equation 2 = − 9 has no real solution, since the square of a real number cannot be negative. Complex numbers provide a solution to this problem; the idea is to extend the real numbers with an indeterminate i, taken to satisfy the relation i2 = −1, so that solutions to equations like the preceding one can be found. In this case the solutions are −1 + 3i and −1 − 3i, as can be verified using the fact that i2 = −1: 2 = 2 = = 9 = − 9, 2 = 2 = 2 = 9 = − 9.
According to the fundamental theorem of algebra, all polynomial equations with real or complex coefficients in a single variable have a solution in complex numbers. In contrast, some polynomial equations with real coefficients have no solution in real numbers; the 16th century Italian mathematician Gerolamo Cardano is credited with introducing complex numbers in his attempts to find solutions to cubic equations. Formally, the complex number system can be defined as the algebraic extension of the ordinary real numbers by an imaginary number i; this means that complex numbers can be added and multiplied, as polynomials in the variable i, with the rule i2 = −1 imposed. Furthermore, complex numbers can be divided by nonzero complex numbers. Overall, the complex number system is a field. Geometrically, complex numbers extend the concept of the one-dimensional number line to the two-dimensional complex plane by using the horizontal axis for the real part and the vertical axis for the imaginary part.
The complex number a + bi can be identified with the point in the complex plane. A complex number whose real part is zero is said to be purely imaginary. A complex number whose imaginary part is zero can be viewed as a real number. Complex numbers can be represented in polar form, which associates each complex number with its distance from the origin and with a particular angle known as the argument of this complex number; the geometric identification of the complex numbers with the complex plane, a Euclidean plane, makes their structure as a real 2-dimensional vector space evident. Real and imaginary parts of a complex number may be taken as components of a vector with respect to the canonical standard basis; the addition of complex numbers is thus depicted as the usual component-wise addition of vectors. However, the complex numbers allow for a richer algebraic structure, comprising additional operations, that are not available in a vector space. Based on the concept of real numbers, a complex number is a number of the form a + bi, where a and b are real numbers and i is an indeterminate satisfying i2 = −1.
For example, 2 + 3i is a complex number. This way, a complex number is defined as a polynomial with real coefficients in the single indeterminate i, for which the relation i2 + 1 = 0 is imposed. Based on this definition, complex numbers can be added and multiplied, using the addition and multiplication for polynomials; the relation i2 + 1 = 0 induces the equalities i4k = 1, i4k+1 = i, i4k+2 = −1, i4k+3 = −i, which hold for all integers k. The real number a is called the real part of the complex number a + bi. To emphasize, the imaginary part does not include a factor i and b, not bi, is the imaginary part. Formally, the complex numbers are defined as the quotient ring of the polynomia
The metre or meter is the base unit of length in the International System of Units. The SI unit symbol is m; the metre is defined as the length of the path travelled by light in vacuum in 1/299 792 458 of a second. The metre was defined in 1793 as one ten-millionth of the distance from the equator to the North Pole – as a result the Earth's circumference is 40,000 km today. In 1799, it was redefined in terms of a prototype metre bar. In 1960, the metre was redefined in terms of a certain 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, i.e. about 39 3⁄8 inches. 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. Other Germanic languages, such as German and the Scandinavian languages spell the word meter. Measuring devices are spelled "-meter" in all variants of English.
The suffix "-meter" has the same Greek origin as the unit of length. The etymological roots of metre can be traced to the Greek verb μετρέω and noun μέτρον, which were used for physical measurement, for poetic metre and by extension for moderation or avoiding extremism; this range of uses is found in Latin, French and other languages. The motto ΜΕΤΡΩ ΧΡΩ in the seal of the International Bureau of Weights and Measures, a saying of the Greek statesman and philosopher Pittacus of Mytilene and may be translated as "Use measure!", thus calls for both measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, the universal measure or standard based on a pendulum with a two-second period; the use of the seconds pendulum to define length had been suggested to the Royal Society in 1660 by Christopher Wren. Christiaan Huygens had observed that length to be 39.26 English inches. No official action was taken regarding these suggestions.
In 1670 Gabriel Mouton, Bishop of Lyon suggested a universal length standard with decimal multiples and divisions, to be based on a one-minute angle of the Earth's meridian arc or on a pendulum with a two-second period. In 1675, the Italian scientist Tito Livio Burattini, in his work Misura Universale, used the phrase metro cattolico, derived from the Greek μέτρον καθολικόν, to denote the standard unit of length derived from a pendulum; as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. On 7 October 1790 that commission advised the adoption of a decimal system, on 19 March 1791 advised the adoption of the term mètre, a basic unit of length, which they defined as equal to one ten-millionth of the distance between the North Pole and the Equator. In 1793, the French National Convention adopted the proposal. In 1791, the French Academy of Sciences selected the meridional definition over the pendular definition because the force of gravity varies over the surface of the Earth, which affects the period of a pendulum.
To establish a universally accepted foundation for the definition of the metre, more accurate measurements of this meridian were needed. The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Méchain, lasting from 1792 to 1799, which attempted to measure the distance between a belfry in Dunkerque and Montjuïc castle in Barcelona to estimate the length of the meridian arc through Dunkerque; this portion of the meridian, assumed to be the same 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. The problem with this approach is that the exact shape of the Earth is not a simple mathematical shape, such as a sphere or oblate spheroid, at the level of precision required for defining a standard of length; the irregular and particular shape of the Earth smoothed to sea level is represented by a mathematical model called a geoid, which means "Earth-shaped". Despite these issues, in 1793 France adopted this definition of the metre as its official unit of length based on provisional results from this expedition.
However, it was determined that the first prototype metre bar was short by about 200 micrometres because of miscalculation of the flattening of the Earth, making the prototype about 0.02% shorter than the original proposed definition of the metre. Regardless, this length became the French standard and was progressively adopted by other countries in Europe; the expedition was fictionalised in Le mètre du Monde. Ken Alder wrote factually about the expedition in The Measure of All Things: the seven year odyssey and hidden error that transformed the world. In 1867 at the second general conference of the International Association of Geodesy held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth; the conference recommended the adoption of the metre and the creation of an internatio
The ohm is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm. Although several empirically derived standard units for expressing electrical resistance were developed in connection with early telegraphy practice, the British Association for the Advancement of Science proposed a unit derived from existing units of mass and time and of a convenient size for practical work as early as 1861; the definition of the ohm was revised several times. Today, the definition of the ohm is expressed from the quantum Hall effect; the ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of one volt, applied to these points, produces in the conductor a current of one ampere, the conductor not being the seat of any electromotive force. Ω = V A = 1 S = W A 2 = V 2 W = s F = H s = J ⋅ s C 2 = kg ⋅ m 2 s ⋅ C 2 = J s ⋅ A 2 = kg ⋅ m 2 s 3 ⋅ A 2 in which the following units appear: volt, siemens, second, henry, kilogram and coulomb.
In many cases the resistance of a conductor in ohms is constant within a certain range of voltages and other parameters. These are called linear resistors. In other cases resistance varies. A vowel of the prefixed units kiloohm and megaohm is omitted, producing kilohm and megohm. In alternating current circuits, electrical impedance is measured in ohms; the siemens is the SI derived unit of electric conductance and admittance known as the mho. The power dissipated by a resistor may be calculated from its resistance, the voltage or current involved; the formula is a combination of Ohm's law and Joule's law: P = V ⋅ I = V 2 R = I 2 ⋅ R where: P is the power R is the resistance V is the voltage across the resistor I is the current through the resistorA linear resistor has a constant resistance value over all applied voltages or currents. Non-linear resistors have a value. Where alternating current is applied to the circuit, the relation above is true at any instant but calculation of average power over an interval of time requires integration of "instantaneous" power over that interval.
Since the ohm belongs to a coherent system of units, when each of these quantities has its corresponding SI unit (watt for P, ohm for R, volt for V and ampere for I, which are related as in § Definition, this formula remains valid numerically when these units are used. The rapid rise of electrotechnology in the last half of the 19th century created a demand for a rational, coherent and international system of units for electrical quantities. Telegraphers and other early users of electricity in the 19th century needed a practical standard unit of measurement for resistance. Resistance was expressed as a multiple of the resistance of a standard length of telegraph wires. Electrical units so defined were not a coherent system with the units for energy, mass and time, requiring conversion factors to be used in calculations relating energy or power to resistance. Two different methods of establishing a system of electrical units can be chosen. Various artifacts, such as a length of wire or a standard electrochemical cell, could be specified as producing defined quantities for resistance, so on.
Alternatively, the electrical units can be related to the mechanical units by defining, for example, a unit of current that gives a specified force between two wires, or a unit of charge that gives a unit of force between two unit charges. This latter method ensures coherence with the units of energy. Defining a unit for resistance, coherent with units of energy and time in effect requires defining units for potential and current, it is desirable that one unit of electrical potential will force one unit of electric current through one unit of electrical resistance, doing one unit of work in one unit of time, otherwi
In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space, carrying electromagnetic radiant energy. It includes radio waves, infrared, ultraviolet, X-rays, gamma rays. Classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light, which, in a vacuum, is denoted c. In homogeneous, isotropic media, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave; the wavefront of electromagnetic waves emitted from a point source is a sphere. The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves of different frequency are called by different names since they have different sources and effects on matter. In order of increasing frequency and decreasing wavelength these are: radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
Electromagnetic waves are emitted by electrically charged particles undergoing acceleration, these waves can subsequently interact with other charged particles, exerting force on them. EM waves carry energy and angular momentum away from their source particle and can impart those quantities to matter with which they interact. Electromagnetic radiation is associated with those EM waves that are free to propagate themselves without the continuing influence of the moving charges that produced them, because they have achieved sufficient distance from those charges. Thus, EMR is sometimes referred to as the far field. In this language, the near field refers to EM fields near the charges and current that directly produced them electromagnetic induction and electrostatic induction phenomena. In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
Quantum electrodynamics is the theory of. Quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation; the energy of an individual photon is greater for photons of higher frequency. This relationship is given by Planck's equation E = hν, where E is the energy per photon, ν is the frequency of the photon, h is Planck's constant. A single gamma ray photon, for example, might carry ~100,000 times the energy of a single photon of visible light; the effects of EMR upon chemical compounds and biological organisms depend both upon the radiation's power and its frequency. EMR of visible or lower frequencies is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules or break chemical bonds; the effects of these radiations on chemical systems and living tissue are caused by heating effects from the combined energy transfer of many photons. In contrast, high frequency ultraviolet, X-rays and gamma rays are called ionizing radiation, since individual photons of such high frequency have enough energy to ionize molecules or break chemical bonds.
These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating, can be a health hazard. James Clerk Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry; because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave. Maxwell's equations were confirmed by Heinrich Hertz through experiments with radio waves. According to Maxwell's equations, a spatially varying electric field is always associated with a magnetic field that changes over time. A spatially varying magnetic field is associated with specific changes over time in the electric field. In an electromagnetic wave, the changes in the electric field are always accompanied by a wave in the magnetic field in one direction, vice versa; this relationship between the two occurs without either type of field causing the other.
In fact, magnetic fields can be viewed as electric fields in another frame of reference, electric fields can be viewed as magnetic fields in another frame of reference, but they have equal significance as physics is the same in all frames of reference, so the close relationship between space and time changes here is more than an analogy. Together, these fields form a propagating electromagnetic wave, which moves out into space and need never again interact with the source; the distant EM field formed in this way by the acceleration of a charge carries energy with it that "radiates" away through space, hence the term. Maxwell's equations established that some charges and currents produce a local type of electromagnetic field near them that does not have the behaviour of EMR. Currents directly produce a magnetic field, but it is of a magnetic dipole type that dies out with distance from the current. In a similar manner, moving charges pushed apart in a conductor by a changing electrical potential produce an electric dipole type electric
In electromagnetics, an evanescent field, or evanescent wave, is an oscillating electric and/or magnetic field that does not propagate as an electromagnetic wave but whose energy is spatially concentrated in the vicinity of the source. When there in fact is an electromagnetic wave produced, one can still identify as an evanescent field the component of the electric or magnetic field that cannot be attributed to the propagating wave observed at a distance of many wavelengths. A hallmark of an evanescent field is. Since the net flow of electromagnetic energy is given by the average Poynting vector, this means that the Poynting vector in these regions, as averaged over a complete oscillation cycle, is zero. In many cases one cannot say that a field is or is not evanescent. For instance, in the above illustration energy is indeed transmitted in the horizontal direction; the field strength drops off exponentially away from the surface, leaving it concentrated in a region close to the interface, for which reason this is referred to as a surface wave.
However, there is no propagation of energy away from the surface, so that one could properly describe the field as being "evanescent in the z direction". This is one illustration of the inexactness of the term. In most cases where they exist, evanescent fields are thought of and referred to as electric or magnetic fields, without the evanescent property being pointed out; the term is applied to differentiate a field or solution from cases where one expects a propagating wave. Everyday electronic devices and electrical appliances are surrounded by large fields, which have this property, their operation involves alternating currents. The term "evanescent" is never heard in this ordinary context. Rather, there may be concern with inadvertent production of a propagating electromagnetic wave and thus discussion of reducing radiation losses or interference. On the other hand, "evanescent field" is used in various contexts where there is a propagating electromagnetic wave involved, to describe accompanying electromagnetic components which do not have that property.
Or in some cases where there would be an electromagnetic wave the term is invoked to describe the field when that wave is suppressed. Although all electromagnetic fields are classically governed according to Maxwell's equations, different technologies or problems have certain types of expected solutions, when the primary solutions involve wave propagation the term "evanescent" is applied to field components or solutions which do not share that property. For instance, the propagation constant of a hollow metal waveguide is a strong function of frequency. Below a certain frequency the propagation constant becomes an imaginary number. A solution to the wave equation having an imaginary wavenumber does not propagate as a wave but falls off exponentially, so the field excited at that lower frequency is considered evanescent, it can be said that propagation is "disallowed" for that frequency. The formal solution to the wave equation can describe modes having an identical form, but the change of the propagation constant from real to imaginary as the frequency drops below the cut-off frequency changes the physical nature of the result.
The solution may be described as a "cut-off mode" or an "evanescent mode". Since the evanescent field corresponding to the mode was computed as a solution to the wave equation, it is discussed as being an "evanescent wave" though its properties are inconsistent with the definition of wave. Although this article concentrates on electromagnetics, the term evanescent is used in fields such as acoustics and quantum mechanics where the wave equation arises from the physics involved. In these cases, solutions to the wave equation resulting in imaginary propagation constants are termed "evanescent" and have the essential property that no net energy is transmitted though there is a non-zero field. In optics and acoustics, evanescent waves are formed when waves traveling in a medium undergo total internal reflection at its boundary because they strike it at an angle greater than the so-called critical angle; the physical explanation for the existence of the evanescent wave is that the electric and magnetic fields cannot be discontinuous at a boundary, as would be the case if there was no evanescent wave field.
In quantum mechanics, the physical explanation is analogous—the Schrödinger wave-function representing particle motion normal to the boundary cannot be discontinuous at the boundary. Electromagnetic evanescent waves have been used to exert optical radiation pressure on small particles to trap them for experimentation, or to cool them to low temperatures, to illuminate small objects such as biological cells or single protein and DNA molecules for microscopy; the evanescent wave from an optical fiber can be used in a gas sensor, evanescent waves figure in the infrared s
International System of Units
The International System of Units is the modern form of the metric system, is the most used system of measurement. It comprises a coherent system of units of measurement built on seven base units, which are the ampere, second, kilogram, mole, a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units; the system specifies names for 22 derived units, such as lumen and watt, for other common physical quantities. The base units are derived from invariant constants of nature, such as the speed of light in vacuum and the triple point of water, which can be observed and measured with great accuracy, one physical artefact; the artefact is the international prototype kilogram, certified in 1889, consisting of a cylinder of platinum-iridium, which nominally has the same mass as one litre of water at the freezing point. Its stability has been a matter of significant concern, culminating in a revision of the definition of the base units in terms of constants of nature, scheduled to be put into effect on 20 May 2019.
Derived units may be defined in terms of other derived units. They are adopted to facilitate measurement of diverse quantities; the SI is intended to be an evolving system. The most recent derived unit, the katal, was defined in 1999; the reliability of the SI depends not only on the precise measurement of standards for the base units in terms of various physical constants of nature, but on precise definition of those constants. The set of underlying constants is modified as more stable constants are found, or may be more measured. For example, in 1983 the metre was redefined as the distance that light propagates in vacuum in a given fraction of a second, thus making the value of the speed of light in terms of the defined units exact; the motivation for the development of the SI was the diversity of units that had sprung up within the centimetre–gram–second systems and the lack of coordination between the various disciplines that used them. The General Conference on Weights and Measures, established by the Metre Convention of 1875, brought together many international organisations to establish the definitions and standards of a new system and standardise the rules for writing and presenting measurements.
The system was published in 1960 as a result of an initiative that began in 1948. It is based on the metre–kilogram–second system of units rather than any variant of the CGS. Since the SI has been adopted by all countries except the United States and Myanmar; the International System of Units consists of a set of base units, derived units, a set of decimal-based multipliers that are used as prefixes. The units, excluding prefixed units, form a coherent system of units, based on a system of quantities in such a way that the equations between the numerical values expressed in coherent units have the same form, including numerical factors, as the corresponding equations between the quantities. For example, 1 N = 1 kg × 1 m/s2 says that one newton is the force required to accelerate a mass of one kilogram at one metre per second squared, as related through the principle of coherence to the equation relating the corresponding quantities: F = m × a. Derived units apply to derived quantities, which may by definition be expressed in terms of base quantities, thus are not independent.
Other useful derived quantities can be specified in terms of the SI base and derived units that have no named units in the SI system, such as acceleration, defined in SI units as m/s2. The SI base units are the building blocks of the system and all the other units are derived from them; when Maxwell first introduced the concept of a coherent system, he identified three quantities that could be used as base units: mass and time. Giorgi identified the need for an electrical base unit, for which the unit of electric current was chosen for SI. Another three base units were added later; the early metric systems defined a unit of weight as a base unit, while the SI defines an analogous unit of mass. In everyday use, these are interchangeable, but in scientific contexts the difference matters. Mass the inertial mass, represents a quantity of matter, it relates the acceleration of a body to the applied force via Newton's law, F = m × a: force equals mass times acceleration. A force of 1 N applied to a mass of 1 kg will accelerate it at 1 m/s2.
This is true whether the object is floating in space or in a gravity field e.g. at the Earth's surface. Weight is the force exerted on a body by a gravitational field, hence its weight depends on the strength of the gravitational field. Weight of a 1 kg mass at the Earth's surface is m × g. Since the acceleration due to gravity is local and varies by location and altitude on the Earth, weight is unsuitable for precision