Q. The length of the resistance wire is increased by 10%. What is the corresponding change in the resistance of wire?
A) 10 %
B) 25 %
C) 21 %
D) 9 %
Explanation
(c) If volume and density remains same, then resistance of wire
$R \propto l^{2}$
Where $l$is the length of the wire
$\therefore R^{'} = \left( 1 + \frac{10}{100}l \right)^{2} = \left( \frac{11}{10} \right)^{2}R$
Hence,
$\frac{R^{'} - R}{R} = \frac{21}{100} = 21\%$
Therefore, change in resistance of wire =21%
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.