For an adiabatic process, the first law of thermodynamics can be written as: Work done by the system = decrease in internal energy of the system
Correct answer: C. Work done on the system = decrease in internal energy of the system
- A. Work done by the system = increase in internal energy of the system
- B. Work done on the system = increase in internal energy of the system
- C. Work done on the system = decrease in internal energy of the system
- D. Work done on the system = decrease in internal energy of the system + heat released
Explanation
In adiabatic process, Q=0, so ΔU = -W. This means that if work is done on the system (W is negative), internal energy increases (ΔU is positive). Conversely, if work is done by system (W is positive), internal energy decreases. Provided options are slightly ambiguous, but core relationship is that work done on system increases internal energy.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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