JEE Main201910 Jan 2019Morning ShiftPhysicsThermodynamicsActual
Three Carnot engines operate in series between a heat source at a temperature T 1 and a heat sink at temperature T 4 (see figure). There are two other reservoirs at temperature T 2 and T 3 , as shown, with T 1 > T 2 > T 3 > T 4 . The three engines are equally efficient if:
Options
- AT 2 = T 1 T 4 2 1 3 ; T 3 = T 1 2 T 4 1 3
- BT 2 = T 1 T 4 1 2 ; T 3 = T 1 2 T 4 1 3
- CT 2 = T 1 2 T 4 1 3 ; T 3 = T 1 T 4 2 1 3
- DT 2 = T 1 3 T 4 1 4 ; T 3 = T 1 T 4 3 1 3
Correct answer
C. T 2 = T 1 2 T 4 1 3 ; T 3 = T 1 T 4 2 1 3
Step-by-step solution
η 1 = 1 - T 2 T 1 η 2 = 1 - T 3 T 2 η 3 = 1 - T 4 T 3 Given η 1 = η 2 = η 3 T 2 T 1 = T 3 T 2 = T 4 T 3 T 2 2 = T 1 T 3 ....(1) T 3 2 = T 2 . T 4 ....(2) From (1) and (2) T 3 = T 1 T 4 2 1 / 3 , T 2 = T 1 2 T 4 1 / 3