An electric heater of resistance 8 Ω draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.

The following formula can be used to compute the rate at which heat develops in the heater.

I2 R = P

We obtain by substituting the numbers in the equation.

P = (15A) ² × 8 Ω = 1800 J/s

Heat is produced at a rate of 1800 J/s by the electric heater.