CBSE Class 11-science Answered

According to the second law of thermodynamics, ''It is impossible to extract an amount of heat Q_H from reservoir and use it all to do work. Some amount of heat energy Q_c must be exhausted to a cold reservoir. This prohibits the posibility of a perfect heat engine''. 

 

Refrigeration is process of cooling a space or substance of a system or maintain its temperature below its ambient temperature. 

In case of refrigerators/heat pumps the work is done in reverse direction i.e. the mechanical energy (work) is converted into heat energy. 

In case of refrigerators and air conditioners the heat is transferred from cold region to hot region. 

 

 

Heat engines are devices that transform heat partly into work or mechanical energy. Heat engines work by using cyclic processes. A heat engine receives heat from a source called reservoir and converts some of it to work. 

 

In case of heat engine, the input given to the working substance is in form of heat energy which then converted to the mechanical work as output.