First law of thermodynamics states that:
Correct answer: A. ΔQ =ΔU+ΔW
- A. ΔQ =ΔU+ΔW
- B. ΔQ =ΔU- ΔW
- C. ΔU =ΔQ+ΔW
- D. ΔW =ΔU+ ΔQ
Explanation
The first law states that heat supplied to a system goes partly into raising its internal energy and partly into work done by the system, so delta Q equals delta U plus delta W. Option c is the same law with work done on the system, a sign convention the FSc course does not use.
This question appeared on the UHS MDCAT 2026 paper, which you can sit online with every answer explained.
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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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