JEE PYQ: Mathematics In Physics Question 9
Question 9 - 2021 (26 Feb Shift 2)
A wire of 1$\Omega$ has a length of 1 m. It is stretched till its length increases by 25%. The percentage change in resistance to the nearest integer is:
(1) 25%
(2) 12.5%
(3) 76%
(4) 56%
Show Answer
Answer: (4)
Solution
For stretched or compressed wire $R \propto l^2$ $\frac{R_1}{R_2} = \frac{l_1^2}{l_2^2}$ $\frac{R_1}{R_2} = \frac{l^2}{(1.25l)^2}$ $\Rightarrow R_2 = 1.5625R$ % increase $\to 56.235%$
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