Q.

A Carnot engine having an efficiency of 1/10 as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is         [2017, 2015]

1 90 J  
2 99 J  
3 100 J   
4 1 J  

Ans.

(1)

The relation between coefficient of performance and efficiency of Carnot engine is given as

       β=1-ηη.                    Given η=110, W=10 J

        β=1-110110=910.10=9

Since, β=Q2W, where Q2 is the amount of energy absorbed from the reservoir

   Q2=βW=9×10=90J