A Carnot engine with sink's temperature at `17^(@)C` has 50% efficiency. By how much should its source temperature be changed to increase its efficiency to 60%

Options

A. 225 K
B. `128^(@)C`
C. 580 K
D. 145 K

Answer

D

Explanation

`eta=1-(T_(2))/(T_(1))`
Initially, `(50)/(100)=1-((273+17))/(T_(1))`
or `(290)/(T_(1))=(1)/(2)`
`implies T_(1)=580K`
Finally, `(60)/(100)=1-((273+17))/(T._(1))`
or `(290)/(T_(1))=(2)/(5)`
`implies T._(1)=725K`
Hence, change in source temperature,
`=(725-580)K`
`=145K`