Question

The temperature of an object is observed to rise during a period. In this period:

• A. heat is certainly supplied to it
• B. heat is certainly not supplied to it
• C. heat may have been supplied to it
• D. work may have been done on it

Answer 1

Answer: (C), (D)

The correct options are
C heat may have been supplied to it
D work may have been done on it

Heat supply during a process depends on molar heat capacity, which may be positive or negative. If positive, then heat is gained otherwise it is lost, e.g for polytropic process $P{V}^x=constant$ with $x>\gamma$ temperature increase is accompanied by heat release.

Using ideal gas equation, $PV=nRT$, increase in $T$ implies increase in at least one of $P$ and $V$.

If $P$ increases and $V$ decreases then $P-V$ work is negative

Hence, options $C$ and $D$ are correct.