The resistance of a wire is$10\,\Omega $. Its length is increased by $10\%$ by stretching. The new resistance will now be .......... $\Omega$
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(a) Since $R \propto {l^2}$ $ \Rightarrow $ If length is increased by $10\%$, resistance is increases by almost $20\%$
Hence new resistance $R' = 10 + 10 $ of $20\%$
$ = 10 + \frac{{20}}{{100}} \times 10 = 12\,\Omega .$
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