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Per NCERT eqn 5.1, the FIRST LAW of thermodynamics is expressed as which equation, with sign conventions?
AΔU = pV
BΔU = q − w (work convention reversed)
CΔU = qT
DΔU = q + w — q positive when heat is absorbed by the system; w positive when work is done ON the system
Answer & Solution
Correct answer: D. ΔU = q + w — q positive when heat is absorbed by the system; w positive when work is done ON the system
Per NCERT eqn 5.1 + IUPAC convention used here, ΔU = q + w. q +ve = absorbed; w +ve = done on system. Energy of an isolated universe is constant.
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