Question

A copper wire has a diameter 0.5 mm and resistivity of 1.6 ×10^-8 what will be the length of the wire to make its resistence 10 ohm? how much does. the resistance change if the diameter is doubled?

plz give full solution not only answer

Answer 1

Given,
diameter of copper wire = 0.5mm = 5 × 10-⁴ m
resistivity = 1.6 × 10^-8 ohm.m
resistance = 10 ohm
Length = ?
we know,
R = dL/A
where R , d , L and A are resistance , resistivity , length and cross section area.

10 = 1.6 × 10^-8 × L/(πr²)
L = 10 × 3.14 × (2.5 × 10^-4)² × 10^8/1.6
L = 10× 3.14 × 6.25/1.6
L = 122.656 m