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11.Thermodynamics
medium
An ideal diatomic gas is heated at constant pressure. The ratio of the work done to the heat supplied is
A
$\frac{3}{5}$
B
$\frac{2}{5}$
C
$\frac{2}{7}$
D
$\frac{4}{7}$
(KVPY-2009)
Solution
(c)
Heat supplied at constant pressure is $\Delta Q=n C_p \Delta T$.
Work done by the gas,
$\Delta W=p \Delta V=n R \Delta T$
Ratio of work done to heat supplied is
$\frac{\Delta W}{\Delta Q}=\frac{n R \Delta T}{n C_p \Delta T}$
$=\frac{R}{C_p}=\frac{C_p-C_V}{C_p}$
$=1-\frac{1}{\gamma}$
$=1-\frac{1}{(7 / 5)}=1-\frac{5}{7}=\frac{2}{7}$
Standard 11
Physics
