Refrigerator is to maintain eatables kept inside at `9^(@)C` . If room temperature is `36^(@)C` Calculate the co- efficient of performance.

An ideal refrigerator keeps its content at 0^(@)C while the room temperature is 27^(@)C .Calculate its coefficient of performance.

When 0.45 kg of ice of 0^(@)C mixed with 0.9 kg of water at 55^(@)C in a container the resulting temperature is 10^(@)C . Calculate the heat of fusion of ice .

An electric heater is used in a room of total wall area 137m^(2) to maintain a temperature of 20^(@)C inside it, when the outside temperature is -10^(@)C .The walls have three different layers of materials. The innermost layer is of wood of thickness 2.5cm, the middle layer is of cement of thickness 1.0cm and the outermost layer is of brick of thickness 25.0cm. Find the power of the electric heater. Assume that there is no heat loss through the floor and the celling. The thermal conductivities of wood, cement and brick are 0.125Wm^(-1)C^(-1) , 1.5Wm^(-1)C^(-1) . and 1.0Wm^(-1)C^(-1) respectively.

Derive an expression for co-efficient of performance of refrigerator.