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P-V Diagrams & Cyclic Processes question from NEET 2018

Q65NEET 2018Medium

P-V Diagrams & Cyclic Processes

The volume (V) of a monatomic gas varies with its temperature (T), as shown in the graph. The ratio of work done by the gas, to the heat absorbed by it, when it undergoes a change from state A to state B, is

Figure

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Answer: (a)

  1. The V-T graph is a straight line through the origin, so V∝TV \propto T: the process A to B is isobaric.
  2. Work W=PΔV=nRΔTW = P\Delta V = nR\Delta T; heat Q=nCPΔTQ = nC_P\Delta T with CP=52RC_P = \frac{5}{2}R for a monatomic gas.
  3. WQ=R52R=25\frac{W}{Q} = \frac{R}{\frac{5}{2}R} = \frac{2}{5}
  4. So the answer is (a) 25\frac{2}{5}.
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