Q. Dimensions of a block are $1\ cm \times 1\ cm \times 100cm.$ If specific resistance of its material is $3 \times 10^{- 7}ohm - m,$ then the resistance between the opposite rectangular faces is
A) $3 \times 10^{- 9}ohm$
B) $3 \times 10^{- 7}ohm$
C) $3 \times 10^{- 5}ohm$
D) $3 \times 10^{- 3}ohm$
Explanation
(b) Length $l = 1\ cm = 10^{- 2}m$
Area of cross-section$\ A = 1\ cm\ \times 100\ cm$
$= 100\ cm^{2} = 10^{- 2}m^{2}$
Resistance $R = 3 \times 10^{- 7} \times \frac{10^{- 2}}{10^{- 2}} = 3 \times 10^{- 7}\ \Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.