1.
Volt
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The volt is the derived unit for electric potential, electric potential difference, and electromotive force. One volt is defined as the difference in potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can also be expressed as amperes times ohms, watts per ampere, or joules per coulomb, for the Josephson constant, KJ = 2e/h, the conventional value KJ-90 is used, K J-90 =0.4835979 GHz μ V. This standard is typically realized using an array of several thousand or tens of thousands of junctions. Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc. in the water-flow analogy sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage is likened to difference in water pressure. Current is proportional to the diameter of the pipe or the amount of water flowing at that pressure. A resistor would be a reduced diameter somewhere in the piping, the relationship between voltage and current is defined by Ohms Law. Ohms Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems, the voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell. Cells can be combined in series for multiples of that voltage, mechanical generators can usually be constructed to any voltage in a range of feasibility. High-voltage electric power lines,110 kV and up Lightning, Varies greatly. Volta had determined that the most effective pair of metals to produce electricity was zinc. In 1861, Latimer Clark and Sir Charles Bright coined the name volt for the unit of resistance, by 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission and they made the volt equal to 108 cgs units of voltage, the cgs system at the time being the customary system of units in science. At that time, the volt was defined as the difference across a conductor when a current of one ampere dissipates one watt of power. The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell and this definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of reproducible units was abandoned in 1948. Prior to the development of the Josephson junction voltage standard, the volt was maintained in laboratories using specially constructed batteries called standard cells

2.
Switched-mode power supply
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A switched-mode power supply is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. Like other power supplies, an SMPS transfers power from a DC or AC source, to DC loads, such as a computer, while converting voltage. Ideally, a power supply dissipates no power. Voltage regulation is achieved by varying the ratio of on-to-off time, in contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. This higher power efficiency is an important advantage of a switched-mode power supply. Switched-mode power supplies may also be smaller and lighter than a linear supply due to the smaller transformer size. Switching regulators are used as replacements for linear regulators when higher efficiency and they are, however, more complicated, their switching currents can cause electrical noise problems if not carefully suppressed, and simple designs may have a poor power factor. 1836 Induction coils use switches to generate high voltages,1910 An inductive discharge ignition system invented by Charles F. Kettering and his company Dayton Engineering Laboratories Company goes into production for Cadillac. The Kettering ignition system is a version of a flyback boost converter. Variations of this system were used in all non-diesel internal combustion engines until the 1960s when it was displaced with capacitive discharge ignition systems. 1926 On 23 June, British inventor Philip Ray Coursey applies for a patent in his country and United States, the patent mentions high frequency welding and furnaces, among other uses. Ca 1936 Car radios used electromechanical vibrators to transform the 6 V battery supply to a suitable B+ voltage for the vacuum tubes,1959 Transistor oscillation and rectifying converter power supply system U. S. 1972 HP-35, Hewlett-Packards first pocket calculator, is introduced with transistor switching power supply for light-emitting diodes, clocks, timing, ROM,1973 Xerox uses switching power supplies in the Alto minicomputer 1977 Apple II is designed with a switching mode power supply. Rod Holt was brought in as engineer and there were several flaws in Apple II that were never publicized. One thing Holt has to his credit is that he created the power supply that allowed us to do a very lightweight computer. 1980 The HP8662A10 kHz –1.28 GHz synthesized signal generator went with a switched mode power supply, a linear regulator provides the desired output voltage by dissipating excess power in ohmic losses. Ideal switching elements have no resistance when closed and carry no current when open and this is because the inductor responds to changes in current by inducing its own voltage to counter the change in current, and this voltage adds to the source voltage while the switch is open. This boost converter acts like a transformer for DC signals

3.
Null vector
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In mathematics, given a vector space X with an associated quadratic form q, written, a null vector or isotropic vector is a non-zero element x of X for which q =0. In the theory of bilinear forms, definite quadratic forms. They are distinguished in only for the latter there exists a nonzero null vector. Where such a vector exists, is called a pseudo-Euclidean space, a pseudo-Euclidean vector space may be decomposed into orthogonal subspaces A and B, X = A + B, where q is positive-definite on A and negative-definite on B. The null cone, or isotropic cone, of X consists of the union of balanced spheres, the null cone is also the union of the isotropic lines through the origin. The light-like vectors of Minkowski space are null vectors, null vectors are also used in the Newman–Penrose formalism approach to spacetime manifolds. A composition algebra splits when it has a vector, otherwise it is a division algebra. In the Verma module of a Lie algebra there are null vectors, dubrovin, B. A. Fomenko, A. T. Novikov, S. P. Translated by Burns, Robert G. Springer, neville, E. H. Prolegomena to Analytical Geometry in Anisotropic Euclidean Space of Three Dimensions