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Physics · PYQ NEET UG 2019(1)
हिन्दीA copper rod of \( 88\text{ cm} \) and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of aluminium rod is: (\( \alpha_{\text{cu}} = 1.7 \times 10^{-5}\text{ K}^{-1} \) and \( \alpha_{\text{Al}} = 2.2 \times 10^{-5}\text{ K}^{-1} \))
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Correct answer · Option B
\( 68\text{ cm} \)
Explanation
The change in length is independent of temperature increase if \( \Delta L_1 = \Delta L_2 \implies L_{\text{cu}}\alpha_{\text{cu}} \Delta T = L_{\text{Al}}\alpha_{\text{Al}} \Delta T \). Thus, \( 88 \times 1.7 \times 10^{-5} = L_{\text{Al}} \times 2.2 \times 10^{-5} \implies L_{\text{Al}} = \frac{88 \times 1.7}{2.2} = 68\text{ cm} \).
