Volt – wikipedia electricity ground explained

One volt is defined as the difference in electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. [2] It is also equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can be expressed in terms of SI base units ( m, kg, s, and A) as V = potential energy charge = N ⋅ m C = kg ⋅ m 2 A ⋅ s 3 . {\displaystyle {\text{V}}={\frac {\text{potential energy}}{\text{charge}}}={\frac {{\text{N}}{\cdot }{\text{m}}}{\text{C}}}={\frac {{\text{kg}}{\cdot }{\text{m}}^{2}}{{\text{A}}{\cdot }{\text{s}}^{3}}}.}

It can also be expressed as amperes times ohms (current times resistance, Ohm’s law), watts per ampere (power per unit current, Joule’s law), or joules per coulomb (energy per unit charge), which is also equivalent to electronvolts per elementary charge: V = A ⋅ Ω = W A = J C = eV e . {\displaystyle {\text{V}}={\text{A}}{\cdot }\Omega ={\frac {\text{W}}{\text{A}}}={\frac {\text{J}}{\text{C}}}={\frac {\text{eV}}{e}}.} Josephson junction definition [ edit ]

The " conventional" volt, V 90, defined in 1988 by the 18th General Conference on Weights and Measures and in use from 1990, is implemented using the Josephson effect for exact frequency-to-voltage conversion, combined with the caesium frequency standard. For the Josephson constant, K J = 2 e/ h (where e is the elementary charge and h is the Planck constant), the "conventional" value K J-90 is used: K J-90 = 0.4835979 GHz μ V . {\displaystyle K_{\text{J-90}}=0.4835979\,{\frac {\text{GHz}}{\mu {\text{V}}}}.}

This standard is typically realized using a series-connected array of several thousand or tens of thousands of junctions, excited by microwave signals between 10 and 80 GHz (depending on the array design). [3] Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc., and no correction terms are required in a practical implementation. [4] Water-flow analogy [ edit ]

In the water-flow analogy, sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage (difference in electric potential) 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 and a capacitor/ inductor could be likened to a "U" shaped pipe where a higher water level on one side could store energy temporarily.

The relationship between voltage and current is defined (in ohmic devices like resistors) by Ohm’s law. Ohm’s Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems. Common voltages [ edit ]

In 1800, as the result of a professional disagreement over the galvanic response advocated by Luigi Galvani, Alessandro Volta developed the so-called voltaic pile, a forerunner of the battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. In 1861, Latimer Clark and Sir Charles Bright coined the name "volt" for the unit of resistance. [9] By 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. [10] In 1881, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force. [11] They made the volt equal to 10 8 cgs units of voltage, the cgs system at the time being the customary system of units in science. They chose such a ratio because the cgs unit of voltage is inconveniently small and one volt in this definition is approximately the emf of a Daniell cell, the standard source of voltage in the telegraph systems of the day. [12] At that time, the volt was defined as the potential difference [i.e., what is nowadays called the "voltage (difference)"] across a conductor when a current of one ampere dissipates one watt of power.

• ^ Burroughs, Charles J.; Bent, Samuel P.; Harvey, Todd E.; Hamilton, Clark A. (1999-06-01), "1 Volt DC Programmable Josephson Voltage Standard", IEEE Transactions on Applied Superconductivity, Institute of Electrical and Electronics Engineers (IEEE), 9 (3): 4145–4149, doi: 10.1109/77.783938, ISSN 1051-8223 , retrieved 2014-06-27

• ^ Keller, Mark W (2008-01-18), "Current status of the quantum metrology triangle" (PDF), Metrologia, 45 (1): 102–109, Bibcode: 2008Metro..45..102K, doi: 10.1088/0026-1394/45/1/014, ISSN 0026-1394, Theoretically, there are no current predictions for any correction terms. Empirically, several experiments have shown that K J and R K are independent of device design, material, measurement setup, etc. This demonstration of universality is consistent with the exactness of the relations, but does not prove it outright.

• Latimer Clark and Sir Charles Bright (1861) "On the formation of standards of electrical quantity and resistance," Report of the Thirty-first Meeting of the British Association for the Advancement of Science (Manchester, England: September 1861), section: Mathematics and Physics, pp. 37-38.

• ^ Sir W. Thomson, et al. (1873) "First report of the Committee for the Selection and Nomenclature of Dynamical and Electrical Units," Report of the 43rd Meeting of the British Association for the Advancement of Science (Bradford, September 1873), pp. 222-225. From p. 223: "The "ohm," as represented by the original standard coil, is approximately 10 9 C.G.S. units of resistance ; the "volt" is approximately 10 8 C.G.S. units of electromotive force ; and the "farad" is approximately 1/10 9 of the C.G.S. unit of capacity."