Question

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. $600K$

Answer 1

Answer: (C)

$750K$

For the 1st case,
Efficiency= $\eta =(1-\frac{T_1}{T_2})\times 100$
$40=(1-\frac{T_1}{500})\times 100$
$T_1=300K$

For the 2nd case,
$\eta =(1-\frac{300}{T_2})\times 100=60$
$T_2=750K$