A Carnot engine, whose efficiency is 40%, takes in heat from a source maintained at a temperature of 500 K It is desired to have an engine of efficiency 60%. Then, the intake temperature for the same exhaust (sink) temperature must be

Options

A. efficiency of carnot engine cannot be made larger than 50 %
B. 1200 K
C. 750 K
D. 600 K

Answer

C

Explanation

For 1st case,
efficiency `=eta=(1-(T_1)/(T_2))xx100`
`(1-(T_1)/(500))xx100=40 implies T_1=300K`
For 2nd case,
`eta=(1-(300)/(T_2))xx100=60`
`T_2=750K`.