A wire of a certain material is stretched slowly by ten percent. New resistance and specific resistance…

A wire of a certain material is stretched slowly by ten percent. New resistance and specific resistance become respectively
  1. 1.1 times, 1.1 times
  2. 1.2 times, 1.1 times
  3. 1.21 times, same
  4. Both remain the same

Solution

$\begin{aligned} & \frac{R_2}{R_1}=\left(\frac{l_2}{l_1}\right)^2=\left(\frac{1.1 l_1}{l_1}\right)^2=1.21 \\ & R_2=1.21 R \end{aligned}$

Asked in: NEET 2008 (Mains)

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