In the diagrams (i) to (iv) variation of volume with changing pressure is shown. A gas is taken along the path ABCD. The change in internal energy of the gas will be:
Correct answer: D. Zero in all four cases
- A. Positive in all cases (i) to (iv)
- B. Negative in cases (i), (ii) and (iii) but zero in (iv) case
- C. Positive in cases (i), (ii) and (iii) but zero in (iv) case
- D. Zero in all four cases
Explanation
In case of any cyclic process change in internal energy is zero. Here, the given four diagrams are representing the cyclic process. So, the change in internal energy will be zero in all four cases.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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