Q. A resistance of $2\Omega$ is to be made from a copper wire (specific resistance=$1.7 \times 10^{- 8}\Omega\ m)$ using a wire of length 50cm. The radius of the wire is
A) 0.0116 mm
B) 0.367 mm
C) 0.116 mm
D) 0.267 mm
Explanation
(b) $A = \pi r^{2} = \frac{\rho l}{R}or\ r = \left( \frac{\rho l}{\pi R} \right)^{1/2}\ $
$r = \left( \frac{1.7 \times 10^{- 8} \times 0.5}{3.14 \times 2} \right)^{1/2} = 0.367\ mm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.