# Volt

VkVvoltskilovoltkilovoltsmillivoltmVmicrovoltmillivoltsVDC
The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force.wikipedia
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### Electromotive force

EMFelectromotive force (EMF)
The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force.
Electromotive force, abbreviated emf (denoted \mathcal{E} and measured in volts), is the electrical action produced by a non-electrical source.

### Voltage

potential differenceVvoltages
The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force. 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.
In the International System of Units, the derived unit for voltage is named volt.

### Electric potential

electrical potentialelectrostatic potentialCoulomb potential
The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force. 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.
), or volts (

### Alessandro Volta

VoltaVolta, AlessandroA. Volta
It is named after the Italian physicist Alessandro Volta (1745–1827).
The SI unit of electric potential is named in his honour as the volt.

### Electric field

electricelectrostatic fieldelectrical field
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.
The SI unit for electric field strength is volt per meter (V/m).

### Watt

kWMWmegawatt
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.
In terms of electromagnetism, one watt is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, however, is used for a different quantity from the real power of an electrical circuit).

### SI derived unit

derived unitderived unitsJ/kg
The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force.

### Ohm's law

ohmicOhmohmic losses
It can also be expressed as amperes times ohms (current times resistance, Ohm's law), webers per second (magnetic flux per time), watts per ampere (power per unit current, definition of electric power), or joules per coulomb (energy per unit charge), which is also equivalent to electronvolts per elementary charge:
is the current through the conductor in units of amperes, V is the voltage measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms.

### Electronvolt

MeVeVkeV
It can also be expressed as amperes times ohms (current times resistance, Ohm's law), webers per second (magnetic flux per time), watts per ampere (power per unit current, definition of electric power), or joules per coulomb (energy per unit charge), which is also equivalent to electronvolts per elementary charge:
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the amount of kinetic energy gained (or lost) by a single electron accelerating from rest through an electric potential difference of one volt in vacuum.

### Coulomb

CPicoCoulomBExacoulomb
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.
Thus, it is also the amount of excess charge on a capacitor of one farad charged to a potential difference of one volt:

### Ohm

Ωohmsmegohm
It can also be expressed as amperes times ohms (current times resistance, Ohm's law), webers per second (magnetic flux per time), watts per ampere (power per unit current, definition of electric power), or joules per coulomb (energy per unit charge), which is also equivalent to electronvolts per elementary charge:
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.

### Joule

JkJMJ
Additionally, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it.
In terms firstly of base SI units and then in terms of other SI units, a joule is defined below, where kg is the kilogram, m is the metre, s is the second, N is the newton, Pa is the pascal, W is the watt, C is the coulomb, and V is the volt:

### Josephson effect

Josephson junctionJosephson junctionsJosephson energy
The "conventional" volt, V 90, defined in 1987 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.
The NIST standard for one volt is achieved by an array of 20,208 Josephson junctions in series.

### Kilogram

kgmgmilligram
It can be expressed in terms of SI base units (m, kg, s, and A) as
Three other base units (cd, A, mol) and 17 derived units (N, Pa, J, W, C, V, F, Ω, S, Wb, T, H, kat, Gy, Sv, lm, lx) in the SI system were defined in relation to the kilogram, and thus its stability was important.

### Hydraulic analogy

drain-pipe theoryelectronic–hydraulic analogelectronic–hydraulic analogy
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.
Electric potential and voltage are usually measured in volts.

### Resistor

Resistor controlresistorsResistance
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.
An ohm is equivalent to a volt per ampere.

### General Conference on Weights and Measures

CGPMConférence Générale des Poids et MesuresCGPM conference
The "conventional" volt, V 90, defined in 1987 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.

### Ampere

AmAamp
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. It can be expressed in terms of SI base units (m, kg, s, and A) as
The standard ampere is most accurately realized using a Kibble balance, but is in practice maintained via Ohm's law from the units of electromotive force and resistance, the volt and the ohm, since the latter two can be tied to physical phenomena that are relatively easy to reproduce, the Josephson junction and the quantum Hall effect, respectively.

### Magnetic flux quantum

Josephson constantFlux quantizationmagnetic flux quanta
For the Josephson constant, K J = 2e/h (where e is the elementary charge and h is the Planck constant), a "conventional" value K J-90 = 0.4835979 GHz/μV was used for the purpose of defining the volt.

### Conventional electrical unit

conventionalConventional electrical unitsconventional value
The "conventional" volt, V 90, defined in 1987 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.

### Capacitor

capacitorscapacitivecondenser
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.
:A capacitance of one farad (F) means that one coulomb of charge on each conductor causes a voltage of one volt across the device.

### Electric battery

batterybatteriesBattery (electricity)
The voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell.
The electrical driving force or across the terminals of a cell is known as the terminal voltage (difference) and is measured in volts.

### Power (physics)

powermotive powerengine power
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.

### Mains electricity by country

electric power systemsMains power systemsList of countries with mains power plugs, voltages and frequencies

### List of railway electrification systems

1.5 kV DC1,500 V DC750V DC