N moles of a monoatomic gas is carried round the reversible rectangular cycle ABCDA as shown in the fig. The temperature at A is T0. The thermodynamic efficiency of the cycle is

QAB=NCVT0QBC=NCp2T0QCD=−NCV2T0QDA=−NCpT0Heat input, Q1=QAB+QBC=NT0CV+2CpHeat lost, Q2=NT02CV+Cp∴ η=1−Q2Q1=1−2Cv+CpCv+2Cp=1−(2+γ)(1+2γ)=1−(2+5/3)(1+2×5/3)=1−(11/3)(13/3)=213=213×100≈15%