Question

Calculate the resistivity of the material $1.5m$ long, having $0.4mm$ diameter and having a resistance of $3ohm$.

Answer 1

Resistance = 3 Ohm

length = 1.2m

diameter = 0.4mm=0.4$\times {10}^{-3}$

Resistivity = ?

R = $\frac{Pl}{A}$

$R=\frac{\rho l}{\pi d^2}$

R = resistance ,P= resistivity , l = length d = diameter

$3=\frac{\rho \times 1.5\times 4}{\pi \times 0.4\times {10}^{-3}\times 0.4\times {10}^{-3}}\rho =\frac{3\times \pi \times 0.4\times 0.4\times {10}^{-6}}{6}\rho =8\pi \times {10}^{-8}\Omega m$