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)

Options

A. Cyclic process: q = -w
B. Adiabatic process: `DeltaU = -w`
C. Ispochoric process : `DeltaU = q`
D. Isothermal process: `q = -w`

Answer

D

Explanation

According to first law of thermodynamics,
`DeltaU = q + w`
For cyclic process, `DeltaU = 0 therefore q = -w`
For adiabatic process, q = 0 `therefore DeltaU = w`
For isochoric process, `DeltaV = 0, w = 0 therefore DeltaU = q`
Fo isothermic process, `DeltaT = 0 therefore q = -w`.