Voltage

Voltage, also known as electric potential difference, electric pressure or electric tension is the difference in electric potential between two points, which (in a static electric field) is defined as the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage (potential difference) is named volt. In SI units other than volts, electric potential is also expressed as joules per coulomb.

Definition

The electric potential difference between two points can be defined as the work done (energy transferred) per unit charge against a static electric field to move the test charge between two points. This definition can be extended to dynamic electric fields when the quasistatic approximation conditions are met. These conditions cover cases where the field changes are slow enough to ensure that the electric field is essentially static on the scale of the charged object's motion.

Units

The SI unit of electric potential is the volt, which is defined as a joule per coulomb. Historically, the volt was defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power. The "conventional" volt, V90, 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.

Hydraulic analogy

The hydraulic analogy compares electric current flowing through circuits to water flowing through pipes. When a pipe (a conductor) is filled with hair (the resistance), it takes a larger pressure (voltage) to achieve the same flow of water (current).

See also

• Electric field
• Electric charge
• Electric current
• Ohm's law
• Kirchhoff's circuit laws
• Electromotive force

References

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