Question

A cornot engine in 1000 kilocal of heat from a reservoir at `627^@C` and exhausts it to sink at `27^@C`. What is its efficiency? How much work does it perform?

Answer 1

Given `T_1=627^@C=627+273=900K`
`T_2=27^@C=27+273=300K`
`Q_1=3000`kcal
(a) `eta=1-(T_2)/(T_1)=1-(300)/(900)=(2)/(3)` i.e., `(200)/(3)=66.6%`
(b) `(Q_2)/(Q_1)=(T_2)/(T_1)implies(Q_2)/(3000)=(300)/(900)`
`Q_2=1000kcal`
`W=Q_1-Q_2=3000-1000=2000kcal`
`=2000xx10^3xx4.2=8.4xx10^6J`