A metal block of heat capacity 80 J/oC placed in a room at 20oC is heated electrically. The heater isswitched off when the temperature reaches 30oC. Thetemperature of the block rises at the rate of 2oC/s justafter the heater is switched on and falls at the rate of0.2oC/s just after the heater is switched off. AssumeNewton's Law of Cooling to hold.(a) Find the power of the heater.(b) Find the power radiated by the block just after the heateris switched off.(c) Find the power radiated by the block when the temperatureof the block is 25oC.(d) Assuming that the power radiated at 25oCrepresents the average value in the heating process, find the timefor which the heater was kept on.

Utkarsh Gupta , 13 Years ago

Grade 12