Heat and Thermodynamics 5 Question 30
31. Which of the following options is the only correct representation of a process in which $\Delta U=\Delta Q-p \Delta V$ ?
(a) (II) (iii) (S)
(b) (II) (iii) (P)
(c) (III) (iii) (P)
(d) (II) (iv) (R)
(2017 Adv.)
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Solution:
$$ \begin{aligned} \Delta U & =\Delta Q-p \Delta V \\ \Delta U+p \Delta V & =\Delta Q \end{aligned} $$
As $\Delta U \neq 0, W \neq 0, \Delta Q \neq 0$. The process represents, isobaric process
$$ W _{gas}=-p(\Delta V)=-p\left(V _2-V _1\right)=-p V _2+p V _1 $$
Graph ’ $P$ ’ satisfies isobaric process.
