When a current of I (in ampere) flows through a resistor of resistance R (in ohm) for time t (in second), then from Joule’s law of heating we can write that, the amount of heat produced in a resistor, H = I²Rt. From the above formula, it can be said that, the amount of heat produced in a resistor is, (i)directly proportional to the square of current(H proportional I²) (ii)directly proportional to the resistance of the resistor (H proportional R) (iii)directly proportional to the time for which the current flows through the resistor (H proportional t)