For an adiabatic expansion of an ideal gas,

Question:

For an adiabatic expansion of an ideal gas, the fractional change in its pressure is equal to (where $\gamma$ is the ratio of specific heats):

  1. $-\gamma \frac{d \mathrm{~V}}{\mathrm{~V}}$

  2. $-\gamma \frac{V}{d V}$

  3. $-\frac{1}{\gamma} \frac{\mathrm{dV}}{\mathrm{V}}$

  4. $\frac{d V}{V}$


Correct Option: 1

Solution:

$\mathrm{PV} \gamma=$ constant

Differentiating

$\frac{\mathrm{dP}}{\mathrm{dV}}=-\frac{\gamma \mathrm{P}}{\mathrm{V}}$

$\frac{\mathrm{dP}}{\mathrm{P}}=-\frac{\gamma \mathrm{dV}}{\mathrm{V}}$

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