A thermodynamic system goes through a cyclic process which absorbs 1200 J heat and ejects 700 J heat. Which statement correctly describes this?
Correct answer: C. The system performs network of 500 J
- A. The ∆E of a system increases by 500 J
- B. The ∆E of a system decreases by 500 J
- C. The system performs network of 500 J
- D. The surroundings perform network of 500 J
Explanation
In a cyclic process the system returns to its starting state, so the change in internal energy is zero. By the first law the net heat absorbed, 1200 minus 700, which is 500 J, must all appear as net work done by the system, printed here as network. The options with internal energy changing by 500 J ignore that the process is cyclic.
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About First Law of Thermodynamics
The first law states that energy is conserved, so the change in a system's internal energy equals heat supplied plus work done on the system, ΔU = q + w. Questions use sign conventions, expansion and compression work, state functions versus path functions, and the relation between internal energy and enthalpy.
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