Question

Which of the following statements is correct for any thermodynamic system?

• A. The internal energy changes in all processes
• B. Internal energy and entropy are state functions
• C. The work done in an adiabatic process is always zero
• D. The change in entropy can never be zero

Answer 1

Answer: (B)

A) Internal energy can remain constant, say for a gas if its temperature doesn't changes as $\Delta U=m{C}_v\Delta T$ = 0 if ΔT is zero in the process

B) Internal energy and entropy are definitely state functions as they depend only on the final and initial states

C) It can be zero if process is fully reversible

D) From the first law, $\Delta W=-\Delta U$ for an adiabatic process so work may be non-zero if ΔU is non zero