THE HEATING EFFECT
When a current is caused to flow through a material, energy is lost as the electrons hit and interact with the metal lattice, this causes increased vibration of the lattice, known as heat. In a purely resistive circuit all the energy lost in circuit is in the form of heat. The potential difference is a measure of energy per unit positive charge, and currant is a measure of rate of charge flow, so the rate of energy transfer is given by the voltage multiplied by current,