Question

Explain the working of refrigerator,how does it maintain such a low temperature,using electricity?

Answer 1

Refrigerator is a Carnot machine. It absorbs heat from the inside of its system and rejects it to the environment.  Refrigerator takes does work in this activity and takes external power from the current supply.

The refrigerant or coolant liquid (gas) can evaporate easily.  When this coolant is compressed it is liquefied.  When it is subject to very low pressure then vaporizes very quickly.  Then coolant absorbs heat energy from the food and beverages inside the fridge, to become vapor.  That is the latent heat of vaporization.  This liquid circulates very close to the compartments inside the fridge and so comes in contact with those compartments.  

   The action of compressing the coolant and then vaporizing it is done by the compressor equipment at the back of fridge. The energy for the compressor and for pumping the coolant is taken from the input power supply from the mains.

   Thus fridge is the opposite of heat engine and it does work to take heat energy from a cold temperature body, and then to reject the heat to the surrounding environment.  The cold bodies and the hot bodies are at constant temperatures.