Question

Resistance of a metal wire of length 1 m is `26 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 ? Using Table `1.1`, predict the material of the wire.

Answer 1

Correct Answer - `1.84 xx 10^-6 Omega m`, manganese
`R = 26 Omega, A = (pi d^2)/(4) = (3.14 xx (0.3 xx 10^-3 m^2))/(4) = 7.065 xx 10^-8 m^2, l =1 m`
As `r = (rho l)/(A), rho = (RA)/(l) = (26 Omega(7.065 xx 10^-8 m^2))/(1 m) = 1.84 xx 10^-6 Omega m`
From Table `3.1`, we find that this is the resistivity of manganese.