A 2kW electric resistance heater submerged in 5 kg water is turned on and kept on for 10 min. During the process 300 kJ of heat is lost from the water the temperature rise of water is.

What is the maximum theoretical COP for a freezer that is maintaining a temperature of -10 degrees celcius and exhausting heat to a kitchen that is 20 degrees celcius?

A solar collector absorbed 40 W/m2 heat from the atmosphere. This is equal to the convection brought by air for drying purpose. If the temperature of the air is 40°C while the solar collector area's temperature is 80°C and neglecting effect of radiation, find the convective heat transfer coefficient.