Thermodynamics Question 306

Question: An ideal gas is subjected to cyclic process involving four thermodynamic states, the amounts of heat (Q) and work (W) involved in each of these states Q1=6000J;Q2=5500J;Q3=3000J Q4=+3500JW1=2500J;W2=1000J;W3=1200JW4=xJ The ratio of the net work done by the gas to the total heat absorbed by the gas is η . The values of x and n respectively are

Options:

A) 500; 7.5%

B) 700; 10.5%

C) 1000; 21%

D) 1500; 15%

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Answer:

Correct Answer: B

Solution:

[b] Q=Q1+Q2+Q3+Q4

=600055003000+3500=+1000J

W=W1+W2+W3+W4

=250010001200+x=+300+x In cyclic process, ΔU=0 Now, Q=ΔU+W

or 1000=0+(300+x)

x=700J

η=WQ1+Q4

=10006000+3500=10.5



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