Consider a rectangular sheet of solid material of length $\ell=9 \mathrm{~cm}$ and width $\mathrm{d}=4…

Consider a rectangular sheet of solid material of length $\ell=9 \mathrm{~cm}$ and width $\mathrm{d}=4 \mathrm{~cm}$. The coefficient of linear expansion is $\alpha=3.1 \times 10^{-5} \mathrm{~K}^{-1}$ at room temperature and one atmospheric pressure. The mass of sheet $\mathrm{m}=0.1 \mathrm{~kg}$ and the specific heat capacity $\mathrm{C}_{\mathrm{v}}=900 \mathrm{~J} \mathrm{~kg}^{-1} \mathrm{~K}^{-1}$. If the amount of heat supplied to the material is $8.1 \times 10^2 \mathrm{~J}$ then change in area of the rectangular sheet is :-
  1. $2.0 \times 10^{-6} \mathrm{~m}^2$
  2. $3.0 \times 10^{-7} \mathrm{~m}^2$
  3. $6.0 \times 10^{-7} \mathrm{~m}^2$
  4. $4.0 \times 10^{-7} \mathrm{~m}^2$

Solution

$\begin{aligned} & \Delta \mathrm{Q}=\mathrm{ms} \Delta \mathrm{T} \\ & 8.1 \times 10^2=0.1 \times 900 \times \Delta \mathrm{T} \\ & \Delta \mathrm{A}=\mathrm{A}_0 2 \alpha \Delta \mathrm{~T}=2.0 \times 10^{-6} \mathrm{~m}^2\end{aligned}$

Asked in: JEE Main 2025 (04 Apr Shift 2)

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