Q. A metal wire of specific resistance $64 \times 10^{- 6}ohm - cm$ and length $198\ cm$ has a resistance of $7\ ohm,$ the radius of the wire will be
A) $2.4\ cm$
B) $0.24\ cm$
C) $0.024\ cm$
D) $24\ cm$
Explanation
(c) $R = \rho\frac{l}{A} \Rightarrow 7 = \frac{64 \times 10^{- 6} \times 198}{\frac{22}{7} \times r^{2}} \Rightarrow r = 0.024cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.