A system consisting of a cylinder full of gas, sealed by a piston, is alternately loaded, heated, unloaded and then cooled back to its original state.
If 78 Joules of work are done, and if 222 Joules of thermal energy are taken out or lost during cooling and other processes, then what is the efficiency of the system?
If 78 Joules of work are done and 222 Joules taken from the system, then 78 J + 222 J = 300 J must have been put into the system.
So the efficiency is
If on every cycle the system does work W and loses thermal energy Qout, then thermal energy Qin = W + Qout must have been put into the system on every cycle. The efficiency is therefore
"efficiency = W / Qin = W / (W + Qin).