Question

Find the resistivity of the given resistor of resistance $25\Omega$?

• A. $12.5\Omega m$
• B. $125\Omega m$
• C. $1.5\Omega m$
• D. $1.25\Omega m$

Answer 1

The correct option is D $1.25\Omega m$

Resistivity of a substance is given by:
$\rho =R\frac{A}{l}$
where:
$R$: Resistance $25\Omega$
$A$: Cross- sectional area $=25c{m}^2=25\times {10}^{-4}{m}^2$
$l$: Length $=5cm=5\times {10}^{-2}m$

Substituting the values, we get

$\rho =25\times \frac{25\times {10}^{-4}}{5\times {10}^{-2}m}=1.25\Omega m$