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11.Thermodynamics
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In a thermodynamics process, pressure of a fixed mass of a gas is changed in such a manner that the gas releases $20\,J$ of heat and $8\,J$ of work is done on the gas. If the initial internal energy of the gas was $30\,J$. The final internal energy will be...... $J$
A
$18$
B
$9$
C
$4.5$
D
$36$
Solution
$d Q=-20 J$
$d W=-8 J$
$V_{i}=30 J$
$d Q=d V+d W$
$d Q=\left(V_{f}-V_{i}\right)+d W$
$-20=\left(V_{f}-30\right)-8$
$-12=V_{f}-30$
$V_{f}=18$
$\therefore$ Final internal energy $=18 J$
Standard 11
Physics
