Calculate the maximum efficiency of an engine operating between 120^o C and 35^o C

Maximum efficiency of an engine working between temperatures T₂ and T₁ is given by the fraction of the heat absorbed by an engine which can be converted into work is known as efficiency of the heat engine.

Mathematically,
Efficiency, η = (T₂ – T₁) / T₂
T₂ = 120^o C = 120 + 273 = 393 K
T₁ = 35^o C = 35 + 273 = 308 K

Therefore,
η = (T₂ – T₁) / T₂
= (393 – 308) / 393
= .21628 = 21.62%

Hence maximum efficiency of the engine is 21.62%