Question

Calculate the cost of operating a heater of 500 W for 20 hours at the rate of Rs 3.90 per unit.

Answer 1

 Power rating of the heater, P = 500 W
      Duration of the operation, t = 20 hours
      Electrical energy consumed = P x t
                                                   = 500 W x 20 hours
                                                   = 10000 W = 10 kW
      Rate for 1 kW = Rs. 3.90
      Total cost of operating = units consumed x rate = 10 x Rs. 3.90 = Rs. 39