Electricity physics

Question

 Resistance of a metal wire of length 1 m is 28 Omega at 20°C. If the diameter of the wire is 0.3 mm, what will be the resistivity of the metal at that temperature?

Answer 1

\(R = \frac{\rho l}{A}\)
\(\rho = \frac{RA}{l}\)

Given R = 28 \(\Omega\)

d = 0.3mm

\(r = 1.5 * 10^{-3}\)m

l = 1m

Therefore, \(\rho =28*2.25*\frac{22}{7} *10^{-6}\)

\(\rho = 22*9*10^{-6}\)

\(\rho = 1.98*10^{-4}\)