Three Carnot engines operate in series between a heat source at a temperature T 1 and a heat sink at…

Three Carnot engines operate in series between a heat source at a temperature T1 and a heat sink at temperature T4 (see figure). There are two other reservoirs at temperature T2 and T3, as shown, with T1>T2>T3>T4. The three engines are equally efficient if:

  1. T2=T1T4213;T3=T12T413
  2. T2=T1T412;T3=T12T413
  3. T2=T12T413;T3=T1T4213
  4. T2=T13T414;T3=T1T4313

Solution

η1=1-T2T1

η2=1-T3T2

η3=1-T4T3

Given η1= η2= η3

T2T1=T3T2=T4T3

T22=T1T3 ....(1)

T32=T2.T4 ....(2)

From (1) and (2)

T3=T1 T421/3,T2=T12T41/3

Asked in: JEE Main 2019 (10 Jan Shift 1)

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