Voltage

The movement of electrons in a conductor requires some form of energy or work, usually provided by an external force, like a battery. This force is called the electromotive force or voltage.

Voltage signifies the energy required to transport a unit charge between two points. It is also referred to as potential difference and is measured in volts.

The plus and minus signs define the direction or polarity of the voltage.

There are two ways to perceive voltage: the potential at point a can be described as V_ab volts higher than the potential at point b, or the potential at point a relative to point b is V_ab.

Additionally, the voltage drop from a to b is equivalent to a voltage rise from b to a.

Voltage can be either constant or time-varying. A constant voltage, usually produced by a battery, is called a DC voltage. It is utilized in portable equipment powered by batteries.

A sinusoidally time-varying voltage produced by electric generators, is an AC voltage. It is supplied to houses for operating appliances.