According to the first law of thermodynamics, if q = heat supplied to the system and W = work done BY the system, then the change in internal energy is

delta_U = q - W
delta_U = q + W
delta_U = delta_q + delta_W
delta_U = delta_q + W

Correct answer: delta_U = q - W

Solution

The first law of thermodynamics states delta_U = q - W, where q is heat absorbed by the system and W is work done by the system. When the system does work, internal energy decreases.

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