Which of the following does not follow first law of thermodynamics ? (W = work , q = heat, `Delta U` = change in internal energy )

Options

A. `W gt 0, q gt 0 Delta U lt 0`
B. `W = 0, q=0 , DeltaU =0`
C. `W gt 0, q=0 Delta U gt 0`
D. ` W lt 0, q lt 0 Delta U lt 0`

Answer

A

Explanation

(a) According to first law of thermodynamics,
`DeltaU=q+W`
`"For "W gt 0,q gt 0,DeltaU=+ve`
`"or "DeltaUgt0`
`"So, that "DeltaU!=q+W" If "Wgt0" and "qgt0`
Hence, it doesn't obey first law of
thermodynamics `( :'DeltaU=q+W)`
(b) When q = 9, W = 0
`DeltaU=0`
`"When "q=0,DeltaU=W," i.e. "DeltaU gt 0" and "W gt 0`
(d) When `q lt 0, W lt 0, DeltaU =-ve`
Thus, `DeltaU lt 0`