Question

A copper wire has diameter 0.5 mm and resistivity 1.6 10^-8Ω m. What will be the length of this wire to make its resistance 10Ω? How much does the resistance change if the diameter is doubled ?

Answer 1

Area of the copper wire A = \(\pi (\frac{D}{2})^2\)

diameter = 0.5 mm = 0.0005 m

Resistance, R = 10W.

Diameter of copper wire is doubled, then diameter

= 2 × 0.5 = 1 mm = 0.001 m

∴ Length of wire = 122.7 m

Resistance of wire = 2.5 W