Science and Mathematics for Engineering 6th Edition by John Bird

Exercise 13

An electric furnace has an efficiency of 62% and is rated at 7.5 kW. 20 kg of copper at 23°C is placed in the furnace until it melts at 1079°C. If the specific heat capacity of copper is assumed to be 0.39 kJ/(kg°C) and the latent heat of fusion is 180 kJ/(kg°C), calculate the time taken for the furnace to melt the copper.