Q. An aluminium (resistivity$\rho = 2.2 \times 10^{- 8}\Omega - m$) wire of a diameter 1.4 mm is used to make a $4\Omega$ esistor. The length of the wire is
A) 220 m
B) 1000 m
C) 280 m
D) 1 m
Explanation
(c) Length of the wire is
$l = \frac{RA}{\rho}$
$\therefore l = \frac{4 \times \pi \times \left( 0.7 \times 10^{- 3} \right)^{2}}{2.2 \times 10^{- 8}} = 280m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.