Q. The resistance of a wire is $10 \,ohm$. It is drawn in order to increase its length by $10 \%$.the new resistance of the wire will be

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A

$8 \, \Omega$

B

$8 \,\Omega$

C

$12 \,\Omega$

D

$15 \,\Omega$

Solution:

if a wire is stretched by $n \%$, resistance increases by $2 n \%$.
therefore, if length is increased by $10 \%$, resistance increases by $20 \%$.
New resistance is $R=10 \Omega+20 \%$ of $10 \Omega=10+2=12 \Omega$.

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