# An ideal Carnot heat engine operates on a temperature difference of $210$ degrees. One third of the heat absorbed from the source is discharged to the sink. If the work done per cycle is $400\; J$. Efficiency $(\eta)$ of an ideal carnot heat engine is

$(a)\;0.52 \\(b)\;0.86 \\(c)\;0.66 \\(d)\;0.77$

The Carnot Efficiency is the theoretical maximum efficiency one can get when the heat engine is operating between two temperatures: The temperature at which the high temperature reservoir operates ( THot ). The temperature at which the low temperature reservoir operates ( TCold ).
Efficiency $(\eta)$ of an ideal carnot heat engine is $0.66$
Hence c is the correct answer.
edited Mar 6