Volt

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• microvolt redirects here

The volt (symbol: V) is the SI derived unit of electric potential difference or electromotive force ^[1]. It is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, the first modern chemical battery.

Contents 1 Definition 1.1 Josephson junction definition 2 Hydraulic analogy 3 Common voltages 4 Voltages in electrophysiology

[edit] Definition

The volt is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power. Hence, it is the base SI representation m² · kg · s^-3 · A^-1, which can be equally represented as one joule of energy per coulomb of charge, J/C.

[edit] Josephson junction definition

Since 1990 the volt is maintained internationally for practical measurement using the Josephson effect, where a conventional value is used for the Josephson constant, fixed by the 18th General Conference on Weights and Measures as

K_{J-90} = 0.4835979 GHz/µV.

[edit] Hydraulic analogy

In the hydraulic analogy sometimes used to explain electric circuits by comparing them to water-filled pipes, voltage is likened to water pressure - it determines how fast the electrons will travel through the circuit. Current (in amperes), in the same analogy, is a measure of the volume of water that flows past a given point, the rate of which is determined by the voltage, and the total output measured in watts. The equation that brings all three components together is: volts × amperes = watts

[edit] Common voltages

[edit] Voltages in electrophysiology

• Nerve cell action potential: around 30 mV

This page uses content from the English-language version of Wikipedia. The original article was at Volt. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License.

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