Question
One mole of diatomic ideal gas undergoes a cyclic process ABC as shown in the figure. The process BC is adiabatic. The temperatures at A, B and C are 400 K, 800 K and 600 K respectively. Choose the correct statement:
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The change in internal energy in the process AB is -350 R.
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The change in internal energy in the process BC is -500 R.
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The change in internal energy in the whole cyclic process is 250 R.
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The change in internal energy in the process CA is 700 R.
Solution
D.
The change in internal energy in the process CA is 700 R.
According to first law of thermodynamics,
(i) change in internal energy from A to B i.e, 
