Question

$3000\text{J}$ of heat is given to a gas at a constant pressure of
$P=2\times {10}^5{\text{N/m}}^2.$
If its volume increases by $10$ litres during the process, find the change in internal energy of the gas. (in Joules)

Answer 1

Given:
$q=3000\text{J}$
$P=2\times {10}^5{\text{N/m}}^2$
$△V=10\times {10}^{-3}{\text{m}}^3$
So,
$W=-P△V=-(2\times {10}^5{\text{N/m}}^2)(10\times {10}^{-3}{\text{m}}^3)=-2\times {10}^3\text{J}$
According to the first law of thermodynamics,
$△U=q+w=3000-2000\text{J}=1000\text{J}$