Question

A Carnot engine, whose efficiency is `40%`, takes in heat from a source maintained at a temperature of 500K. It is desired to have an engine of efficiency `60%`. Then, the intake temperature for the same exhaust (sink) temperature must be:
A. efficiency of carnot engine cannot be made larger than `50%`
B. `1200K`
C. `750K`
D. `600 K`

Answer 1

Correct Answer - C
Here, `eta_(1)= 40%, T_(1)= 500K, T_(2)= T`
`eta_(2)= 60%, T_(1)=?, T_(2)=T`
From `eta= 1-(T_(2))/(T_(1))`
`(40)/(100)=1 -T/(500), T= 300K`
`(60)/(100)= 1 -(300)/(T_(1)), T_(1)= 750 K`