Power is rate of expending energy. Watt is the unitfor power
(joule per second (J/s)). The difference in potentials between
two points is equal to the energy per unit charge and this is
required to move electric charge between the points, as we
know, electric current measures the charge per unit time (in
coulombs/second). The electric power pis given by the product
of the current I and the voltage V (in joules/second = watts)