The resistance of a metal wire of length 1 m is 25 Ω at 20° C. If the diameter of the wire is 0.3 mm, What must be the resistivity of metal at that temperature?

We have,

Length of the metal wire, l = 1 m

Diameter of the wire, d = 0.3 mm

Radius, r = 0.3/2 mm = 0.15 mm

= 0.15 x 10^-3 m

Resistance of the metal, R = 25 Ω

Thus,

Resistivity (ρ) =

⇒ ρ =

⇒ ρ =

⇒ ρ = 1.9625 × 10^-6 Ωm

The resistivity of the metal is 1.9625 × 10-6 Ωm