A source supplies heat to a system at the rate of 1000 W. If the system performs work at a rate of 200 W. The rate at which internal energy of the system increase is
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Question

A source supplies heat to a system at the rate of 1000 W. If the system performs work at a rate of 200 W. The rate at which internal energy of the system increase is

G1 Physics · Accepted Answer

Use the first law of thermodynamics in rate form: dQ/dt = dU/dt + dW/dt Given: dQ/dt = 1000 W dW/dt = 200 W Therefore, dU/dt = 1000 − 200 = 800 W Hence the internal energy increases at 800 W. Option C follows.