1. The problem statement, all variables and given/known data Show that the net work done by the otto engine per cycle is Cv(Tc - Tb)(1 - Ta/Tb) PV diagram: [PLAIN]http://www.antonine-education.co.uk/physics_a2/options/module_7/topic_4/Otto_indic.gif [Broken] 2. Relevant equations Work done by a kmole of gas expanding irreversibly and adiabatically from P1 V1 T1 to P2 V2 T2: = (P1V1 - P2V2)/(γ - 1) = R(T1 - T2)/(γ - 1) 3. The attempt at a solution The only work done by the otto engine is during the adiabatic expansions/compressions. So the work done by the gas from point A to point B is = R(Ta - Tb)/(γ - 1) Likewise, the work done by the gas from point C to point D is = R(Tc - Td)/(γ - 1) So the net work done by the gas will be = R(Ta - Tb)/(γ - 1) + R(Tc - Td)/(γ - 1) = (R/(γ - 1))(Ta - Tb + Tc - Td) = Cv[(Tc - Tb) + Ta - Td] Here I get stuck. I don't see why the answer doesn't have a Td term. Have I gone wrong somewhere?