Q. A wire 20 cm long and 1 $mm^{2}$in cross-section carries a current of 4A when connected to a 2V battery. The resistivity of the wire is
A) $2 \times 10^{- 7}\Omega\ m$
B) $5 \times 10^{- 7}\Omega\ m$
C) $4 \times 10^{- 6}\Omega\ m$
D) $1 \times 10^{- 6}\Omega\ m$
Explanation
(d) $\rho = R\frac{A}{l} = \frac{V}{i} \times \frac{A}{l} = \frac{2}{4} \times \frac{10^{- 6}}{0.5} = 10^{- 6}\Omega m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.