The internal energy of the system decreases in an adiabatic process. Which of the following must be true regarding this process?
Correct answer: B. Work is done by the system
- A. Heat flows out of the system
- B. Work is done by the system
- C. Work is done by the surrounding
- D. The potential energy of the system is changing
Explanation
By first law of Thermodynamics, Q= U + WQ= heat energy supplied to the systemU= internal energyW= Work done by the systemIf work is done on the system then W will be replaced by -W For an adiabatic process Q=0 U+ W = 0 W = -UThis means as work done increases, the internal energy of the system decreases.Thus we conclude that work is done by the system.Hence (B) is the answe
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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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