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.

Solution:

The rate at which the heat develops in the heater can be calculated using the following formula

P = I² R

Substituting the values in the equation, we get

P = (15A) ² × 8 Ω = 1800 watt

The electric heater produces heat at the rate of 1800 watt