Heating up wires

As free electrons flow through wires, they collide with the ions in the wire which causes the ions to vibrate more.

This increased vibration of the ions increases the temperature of the wire.

Energy has been transferred from the electrical energy carried by the electrons into the internal energy of the wire.

Electric power

The electric power (or the amount of energy transferred each second) can be calculated using the equation:

power = current × voltage

P = VI


power = current × potential difference

P = electric power in watts, W

I = current in amperes, A

V = voltage in volts, V

{P} = {VI} {P} = {V}\times{I}
{I} =\frac{\text{P}}{\text{V}} {I} = {P} \div {V}
{V} = \frac{\text{P}}{\text{I}} {V} = {P} \div {I}

Remember that one watt is equal to one joule per second (1 W = J/s).