Question

Find the Resistivity.
If the length of the wire is 50 cm and the radius is 0.5mm, find the resistivity of wire if its resistance is 30 ohms.

Answer 1

Resistance = resistivity * length / area
30 = (resistivity * 0.5) / (0.0005 * 0.0005 * 3.14)
30 = resistivity * 636943
resistivity = 4.7 * 10^-5 ohm m.

Answer 2

R = 30 ohm
l = 50cm = 0.5m
r = 0.5mm = 5×10^(-4)m
$\rho$ =?

$R= \rho \frac{l}{A} \\ \\ \rho = \frac{RA}{l}= \frac{30 \times \pi \times (5\times 10^{-4})^2}{0.5}\\ \\ \rho=4.7 \times 10^{-5}\ ohm\ meter$