System absorbs 500 J of heat and does 300 J of work. The change in internal energy is:
Correct answer: A. 200 J
- A. 200 J
- B. 800 J
- C. -200 J
- D. 500 J
Explanation
By the first law of thermodynamics, ΔU = Q - W, where Q = 500 J (heat absorbed) and W = 300 J (work done by the system). Thus, ΔU = 500 - 300 = 200 J.
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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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