The change in internal energy can be defined as:
Correct answer: B. Q-W
- A. ∆U-W
- B. Q-W
- C. P∆V
- D. Q+W
Explanation
The correct answer is Q-W according to the first law of thermodynamics, which defines the change in internal energy (∆U) as the heat added to the system minus the work done by the system. Option A (∆U-W) is incorrect because it doesn't correctly relate the terms. Option C (P∆V) only considers work done in an isobaric process and ignores heat transfer. Option D (Q+W) incorrectly adds heat and work instead of subtracting work from heat.
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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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