When a body is falling through a gravitational field, it is losing gravitational potential energy.

Similarly, when a charge is "falling" through an electric field, it is losing electric potential energy.

In the situation shown in the diagram above, the water has more gravitational potential energy at A than at B so it falls. The potential energy lost by 1kg of water in falling from level A to level B is the gravitational potential difference between A and B.

To measure voltage we use a voltmeter.

The unit of voltage is the volt.

A voltmeter gives us a reading which indicates the amount of energy lost by each Coulomb of charge moving between the two points to which the voltmeter is connected. 1V means 1JC^-1.

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