Which statement about the first law of thermodynamics is correct?
Correct answer: B. The increase in the internal energy of a system equals the heating of the system minus the work done by the system
- A. The heating of a system equals the increase of its internal energy plus the work done on the system
- B. The increase in the internal energy of a system equals the heating of the system minus the work done by the system
- C. The increase in the internal energy of a system equals the heating of the system plus the work done by the system
- D. The work done on a system equals the increase of its thermal energy plus the heating of the system
Explanation
The first law of thermodynamics is essentially a statement of energy conservation. It states that the increase in the internal energy of a system is equal to the energy added to the system as heating minus the energy lost as work done by the system. Option B is correct as it accurately encapsulates this principle. Option A incorrectly adds the work done on the system without considering it should be subtracted in such a context. Option C incorrectly suggests that work done by the system adds to the increase in internal energy, which is not the case. Option D does not properly incorporate the concept of internal energy, which is crucial to the first law.
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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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