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A thermodynamic system receives 40 J of heat and performs 8 J of work on the surroundings. What is the change in the internal energy of the system?

1. 32 J
2. 40 J
3. 48 J
4. -32 J

Correct answer: 32 J

Solution

By the first law, delta_U = Q - W = 40 - 8 = 32 J. The internal energy increases by 32 J.

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