Question

A4.0m long wire has a diameter of 0.30mm. If its resistance is 30 ohm .find its resistivity and conductivity.

Answer 1

Formula :

R = p × l / a

Given :

l = 4 m

= > l = 4 m

d = 0.3 mm

= > r = d / 2

= > r = 0.3 mm / 2

= > r = 0.15 mm

= > r = 0.15 mm × 10⁻³ m

R = 30 ohms

Resistivity ( p ) = ?

R = p × l / a

= > 30 = p × 4 / 0.15 × 10⁻³

= > 30 = p × 4 × 10³ × 100 / 15

= > 30 × 15 = p × 4 × 10⁵

= > p = 450  / ( 4 × 10⁵ )

= > p = 112.5 × 10⁻⁵

= > p = 1.125 × 10⁻⁸

Conductivity = 1 / p

                     = 1 / 1.125 × 10⁻⁸

                     = 1.125 × 10⁸

ANSWER :

Resistivity =  1.125 × 10⁻⁸

Conductivity = 1.125 × 10⁸

Hope it helps !

_______________________________________________________________