All the electrical power dissipated in a circuit by resistors is in the form of heat energy.
As the electrons move through a resistor, they lose potential energy.
A charge Q will lose potential energy of QV where V is the potential difference across the resistor.
The potential energy of the electrons drops due to the inelastic collisions between the electrons and atoms or ions in the resistive materials and the electrical energy is transferred to heat energy by the collisions.
Since
| Potential difference | = | energy transferred
charge |
and
and
| Power | = | energy transferred
time |
Therefore:
Power = potential difference × current.
P = VI
power = p.d. x current
combining with Ohms law V = IR