Q. The resistance of a wire is $10\Omega.$ Its length is increased by 10% by stretching. The new resistance will now be
A) $12\Omega$
B) $1.2\Omega$
C) $13\Omega$
D) $11\Omega$
Explanation
(a) Since $R \propto l^{2} \Rightarrow$ If length is increased by 10%, resistance increases by almost 20%
Hence new resistance $R^{'} = 10 + 20\%$ of $10$
$= 10 + \frac{20}{100} \times 10 = 12\ \Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.