Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R.
**Assertion A:** If $dQ$ and $dW$ represent the heat supplied to the system and the work done on the system respectively, then according to the first law of thermodynamics $dQ=dU-dW$.
**Reason R:** First law of thermodynamics is based on law of conservation of energy.
In the light of the above statements, choose the correct answer from the options given below:
Answer: (C) Both A and R are correct and R is the correct explanation of A
Energy conservation gives $dU = dQ + dW_{on}$ (heat supplied plus work done on the system both raise the internal energy). Hence $dQ=dU-dW$ with $dW$ the work done on the system, so A is correct.
R is correct and is exactly the principle from which A follows.
Solution by Sreeraj P, M.Sc Physics