Q70 / 75 · JEE Main 2025 (2 Apr Shift 2) · Physics
The internal energy of air in $4 \mathrm{~m} \times 4 \mathrm{~m} \times 3 \mathrm{~m}$ sized room at 1 atmospheric pressure will be _______ $\times 10^6 \mathrm{~J}$. (Consider air as diatomic molecule)
Correct answer: 12
Solution
To find the internal energy of gas in the room.
$\begin{aligned}<br/>& \mathrm{U}=\mathrm{nC}_{\mathrm{v}} \mathrm{~T}=\mathrm{n} \frac{5 \mathrm{RT}}{2} \\ & =\frac{5}{2} \mathrm{PV}=\frac{5}{2} \times 10^5 \times 48=12 \times 10^6 \mathrm{~J}<br/>\end{aligned}$
$\begin{aligned}<br/>& \mathrm{U}=\mathrm{nC}_{\mathrm{v}} \mathrm{~T}=\mathrm{n} \frac{5 \mathrm{RT}}{2} \\ & =\frac{5}{2} \mathrm{PV}=\frac{5}{2} \times 10^5 \times 48=12 \times 10^6 \mathrm{~J}<br/>\end{aligned}$
Hence, the correct answer is 12.