If I is the current flowing through a conductor of resistance R in time t, then the quantity of charge flowing is, q = It. If the charge q, flows between two points having a potential difference V, then the work done in moving the charge is = V. q = V It.
Then, electric power is defined as the rate of doing electric work.
so, Power = Work done / Time = VIt/t = VI
Electric power is the product of potential difference and current strength.
Since V = IR, Power = I2R