NEET Solved Paper 2019 Question 45
Question: A copper rod of 88 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 _{Cu}}=1.7\times 10^{5}K^{1}and,{\alpha _{Al}}= $ $ ~2.2\times 10^{5}K^{1}) $ -[NEET 5-5-2019]
Options:
A) 88 cm
B) 68 cm
C) 6.8 cm
D) 113.9 cm
Show Answer
Answer:
Correct Answer: B
Solution:
$ \Delta {\ell_1}=\Delta {\ell_2} $
$ {\ell_1}{\alpha_1}={\ell_2}{\alpha_2} $
$ \frac{{\ell_1}}{{\ell_2}}=\frac{{\alpha_2}}{{\alpha_1}} $
$ \frac{88}{{\ell_a}}=\frac{2.2\times {10^{-5}}}{1.7\times {10^{-5}}} $
$ {\ell_a}=68cm $
Comment: In this question it should be difference in length instead of increase in length.
