Question

Dimensions of a block are $1cm\times 1cm\times 100cm$. If specific resistance of its material is $3\times {10}^{-7}$ ohm - m, then the resistance between it’s 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

Answer 1

The correct option is B $3\times {10}^{-7}$ ohm


Length l = 1 cm $={10}^{-2}m$
Area of cross-section $A=1cm\times 100cm$
$=100c{m}^2={10}^{-2}{m}^2$
Resistance R $=3\times {10}^{-7}\times \frac{{10}^{-2}}{{10}^{-2}}=3\times {10}^{-7}\Omega$