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Question: Answered & Verified by Expert
A reservoir is at 827 °C and Carnot's engine takes a thousand kilocalorie of heat from it and exhausts it to a sink at 27 °C. What is the amount of work and the efficiency of the engine?
PhysicsThermodynamicsBITSATBITSAT 2018
Options:
  • A 2.7×105 cal, 70.70 %
  • B 7.27×105 cal, 72.72 %
  • C 2.70×105 cal, 80.70 %
  • D 3.70×105 cal, 70.70 %
Solution:
1583 Upvotes Verified Answer
The correct answer is: 7.27×105 cal, 72.72 %

Given, Q1=106 cal

T1=827 °C=(827+273)=1100 K,

T2=27 °C=(27+273)=300 K.

As,   Q1T1=Q2T2

  Q2=T2T1Q1=3001100×106=2.72×105 cal
work done, W=Q1-Q2=106-2.72×105=7.27×105 cal

The efficiency of the engine,
η=1-T2T1×100

η=1-3001100×100

=72.72 %

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