An alternative definition is that it is the potential energy of a unit positive charge placed at that point with the zero being at infinity

The electric potential (V

The unit of electrostatic potential is the volt (V).

The variation of potential with distance from a charge Q is shown in Figure 1.

If a charge q is in the field then its potential energy is given by :

and this is measured in joules.

When one positive charge moves away from another positive charge its potential energy is decreased but when a negative charge is moved away from a positive charge (e.g. electron and proton) its potential energy increases.

The variation of potential energy with distance is shown in Figure 2.

1. Calculate the charge that produces a potential of 12 V at a distance of 0.1 nm in a vacuum.

Using:

V

2. Calculate the force on a charge of 3x10

Force = EQ = 3x10

3. Calculate the potential energy of a charge of 10

Potential energy = (1/4pe