What is the definition of 1 volt

The volt is the derived SI unit of electrical voltage with the unit symbol V. The volt is named after the Italian physicist Alessandro Volta.


The electrical voltage of one volt between two points of a homogeneous, evenly tempered line conductor is present when the power of one watt is converted between these two points with a stationary current of one ampere.

The following applies in formula symbols: "Voltage is work capacity per amount of charge"

International is the symbol for tension E., in the Anglo-Saxon-speaking area also often one V (Voltage).

Practical definition

Since the above definition can hardly be used as an exact reference in practice, one volt has been determined since 1990 using the Josephson effect and the Josephson constant, the reciprocal of the magnetic flux quantum. This constant is:

= 4,835979 1014 Hz / V

This means that the definition of one volt for reference measurements can be traced back to a very precise frequency measurement (time measurement).

Historical definition

Previously the definition of one volt was derived from the Weston normal element. This element delivers an electrical voltage of at a temperature of exactly 20 ° C

UN = 1.01865 V.

Decimal multiples and parts of volts

Surname Yotta Zetta Exa Peta Tera Giga Mega kilo Hecto Deka
symbol Y Z E. P T G M. k H there
factor 1024 1021 1018 1015 1012 109 106 103 102 101
Surname Yocto Zepto Atto Femto Pico Nano Micro Milli Centi Deci
symbol y z a f p n µ m c d
factor 10−24 10−21 10−18 10−15 10−12 10−9 10−6 10−3 10−2 10−1

See also prefixes for units of measure.

Common parts

One kilovolt, kV, corresponds to 1,000 volts: 1 kV = 103 V. It is used especially in power engineering for high voltages.

One millivolt, abbreviated mV, corresponds to the thousandth of a volt: 1 mV = 10-3 V or 0.001 V. This sub-unit is used in electronics, which also work with low voltages.

See also

  • Electricity - an overview of the subject

Categories: SI unit | Electric unit