A copper rod of length 88cm and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of the aluminium rod is
(αCu=1.7×10−5K−1and αAl=2.2×10−5K−1)
A
6.8cm
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B
113.9cm
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C
88cm
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D
68cm
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Solution
The correct option is D68cm Since, the elongation is same for both the rods, (Δl)Cu=(Δl)AllCuαCuΔT=lAlαAlΔT88×1.7×10−5=l2×2.2×10−5lAl=68cm