Find the efficiency of a process in which 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. The system does 25.2 Joules of work, and 254.8 Joules of thermal energy are removed or dissipated during a cycle.
If 25.2 Joules of work are done and 254.8 Joules taken from the system, then 25.2 J + 254.8 J = 280 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).