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NEET 2019
Exam
NEET
Year
2019
Subject
Physics
Chapter
Thermal Properties of Matter

NEET 2019 · Physics · Thermal Properties of Matter

A copper rod of 88cm and an aluminum rod of unknown length have...

A copper rod of 88cm88cm and an aluminum rod of unknown length have their increase in length independent of increase in temperature. The length of aluminum rod is (αCu=1.7×10−5K−1andαAl=2.2×10−5K−1)\left({\alpha}_{Cu} = 1.7 \times {10}^{- 5}{K}^{- 1}and{\alpha}_{Al} = 2.2 \times {10}^{- 5}{K}^{- 1}\right)

Options

  1. A6.8cm6.8cm
  2. B113.9cm113.9cm
  3. C88cm88cm
  4. D68cm68cm

Correct answer

D. 68cm68cm

Step-by-step solution

Increase in length is independent of temperature,
Lcuαcu=LAlαAl{L}_{cu}{\alpha}_{cu} = {L}_{\text{Al}}{\alpha}_{Al}
LAl=(88cm)(1.7×10−5)(2.2×10−5){L}_{Al} = \left(88cm\right)\dfrac{\left(1.7 \times {10}^{- 5}\right)}{\left(2.2 \times {10}^{- 5}\right)}
=68cm= 68cm
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