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Question: Answered & Verified by Expert
Two rods $A$ and $B$ of identical dimensions are at temperature $30^{\circ} \mathrm{C}$. If $\mathrm{A}$ is heated upto $180^{\circ} \mathrm{C}$ and $\mathrm{B}$ upto $\mathrm{T}^{\circ} \mathrm{C},$ then the new lengths are the same. If the ratio of the coefficients of linear expansion of $\mathrm{A}$ and $\mathrm{B}$ is $4: 3,$ then the value of $T$ is
PhysicsThermal Properties of MatterJEE MainJEE Main 2019 (11 Jan Shift 2)
Options:
  • A $230^{\circ} \mathrm{C}$
  • B $270^{\circ} \mathrm{C}$
  • C $200^{\circ} \mathrm{C}$
  • D $250^{\circ} \mathrm{C}$
Solution:
1594 Upvotes Verified Answer
The correct answer is: $230^{\circ} \mathrm{C}$
Change in length in both rods are same i.e.

$\Delta \ell_{1}=\Delta \ell_{2}$

$\ell \alpha_{1} \Delta \theta_{1}=\ell \alpha_{2} \Delta \theta_{2}$

$\begin{array}{l}

\frac{\alpha_{1}}{\alpha_{2}}=\frac{\Delta \theta_{2}}{\Delta \theta_{1}} \quad\left[\because \frac{\alpha_{1}}{\alpha_{2}}=\frac{4}{3}\right] \\

\frac{4}{3}=\frac{\theta-30}{180-30}

\end{array}$

$\theta=230^{\circ} \mathrm{C}$

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