In a cold storage, ice melts at the rate of 2 kg/h when the external temperature is 200C. Find the minimum power output of the motor used to drive the refrigerator which just prevents the ice from melting. Latent heat of fusion of ice = 80 cal/g.

ω = T2T1-T2 = 273293-273 = 27320Mass of ice melting per second = 2×10003600= (59)gTo prevent the melting of ice, heat to be driven out per second, i.e., Q2 = (59)×80 = 4009cal = 44.44 JAs, ω = Q2W, W =Q2ω = 44.44(27320) = 3.25 WPower of the motor = 3.25 W