Question

The resistance between two rectangular faces of a block of dimensions $4cm\times 4cm\times 10$ cm of maganin $(\rho =48\times {10}^{-8}ohmm)$, will be

• A. $4.8\mu \Omega$
• B. $3.8\mu \Omega$
• C. $30\mu \Omega$
• D. $3\mu \Omega$

Answer 1

The correct option is A $4.8\mu \Omega$

The rectangular faces have a surface area(A) of $4\times 10=40c{m}^2=4.0\times {10}^{-3}{m}^2$.

The length(L) of the resistor is thus 4 cm $=4\times {10}^{-2}m$
Using R$=\frac{\rho \times L}{A}$,

We get R $=\frac{48\times {10}^{-8}\times 4\times {10}^{-2}}{{10}^{-3}{m}^2}=4.8\mu \Omega$