Heat and Thermodynamics 5 Question 39
40. For an ideal gas
(1989, 2M)
(a) the change in internal energy in a constant pressure process from temperature $T _1$ to $T _2$ is equal to $n C _V\left(T _2-T _1\right)$, where $C _V$ is the molar heat capacity at constant volume and $n$ the number of moles of the gas
(b) the change in internal energy of the gas and the work done by the gas are equal in magnitude in an adiabatic process
(c) the internal energy does not change in an isothermal process
(d) no heat is added or removed in an adiabatic process
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Answer:
Correct Answer: 40. (a, b, c, d)
Solution:
- (a) $\Delta U=n C _V \Delta T=n C _V\left(T _2-T _1\right)$ in all processes
(b) In adiabatic process $\Delta Q=0$
$\therefore \quad \Delta U=-\Delta W$ or $|\Delta U|=|\Delta W|$
(c) In isothermal process $\Delta T=0$
$\therefore \quad \Delta U=0 \quad$ (as $\left.\Delta U=n C _V \Delta T\right)$
(d) In adiabatic process $\Delta Q=0$
$\therefore$ All the options are correct.
