Question

A monoatomic gas expands at constant pressure on heating. The percentage of heat supplied that increases the internal energy of the gas and that is involved in the expansion is

• A. 75%, 25%
• B. 25%, 75%
• C. 60%, 40%
• D. 40%, 60%

Answer 1

Answer: (C)

60%, 40%

Answer 2

Fraction of energy supplied for increment in internal energy $= \frac{1}{\gamma} = \frac{3}{5}$ $\left\lbrack \text{As }\gamma = \frac{5}{3}\text{for monoatomic gas} \right\rbrack$

∴ Percentage energy $= \frac{30}{5} = 60\%$

Fraction of energy supplied for external work done

$= 1 - \frac{1}{\gamma} = \frac{\gamma - 1}{\gamma} = \frac{\frac{5}{3} - 1}{\frac{5}{3}} = \frac{2}{5}$

∴ Percentage energy$= \frac{2}{5} \times 100\% = 40\%$.