Question

When 20 joules of work is done on a gas , 40 joules of heat energy was released . If the initial internal energy of a gas was 70 joules , what is the final internal energy.

Answer 1

Explanation:

The correct answer is option(A).

Change in internal energy is:

ΔU=Ufinal−Uinitial...........(i)

According to first law of thermodynamics, 

ΔU=Q−W........(ii)

Aaccording to the question,

Q=−Q (energy released in the system)

and, W=−W, (work done on the system).

So, equation (ii) becomes, 

Ufinal−Uinitial=−Q+W

Ufinal=70−40+20=50J

Answer 2

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