Question

Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas ? (Assume non-expansion work is zero)

• A. Cyclic process : $q = - w$
• B. Isothermal process : $q = - w$
• C. Adiabatic process : $\Delta U = - w$
• D. Isochoric process : $\Delta U = q$

Answer 1

Answer: (C)

For cyclic process : $\Delta U = 0 \; \Rightarrow \; q = - w$
For isothermal process : $\Delta U = 0 \; \Rightarrow \; q = - w $
For adiabatic process : $q = 0 \; \Rightarrow \; \Delta U = W$
For isochoric process : $w = 0\; \Rightarrow \; \Delta U = q $