In a motor, the electrical power input is 500 W and the mechanical power output is 0 . 54 horse power. The heat developed in the motor in 1 hour is (assuming that all the electric energy which is not converted to mechanical energy is converted to heat) is

Step-by-step solution

Efficiency = 0.54 × 7 4 6 5 0 0 = 0.80 or 80 % ( 0 . 5   kW   =   500   W and 0 . 54   hp   =   0 . 54 × 746   W ) ∴ 80% of the electrical energy is converted to mechanical energy and the rest 20% is converted to heat energy. ∴    2 0 1 0 0 × 5 0 0 = 1 0 0 W of power is converted to heat ∴ Heat produced in 1h (or 3600 s)   =   100 × 3600   =   36 × 10 4   J = 3 6 × 1 0 4 4.18 cal = 8.6 &#2