Question

A copper wire has a diameter of 0.5mm and a resistivity 0f 1.6x10^-6 ohm cm. How much of this wire would be required to make a 10ohm coil? How much does the resistance change if the diameter is doubled ?

Answer 1

Given:

d = 0.5mm = 5 x 10^-4 m

ρ = 1.6 x 10^-6 Ω cm = 1.6 x 10^-8 Ωm

R = 10 Ω

⇒ l = RA/ρ = 122.72 m

Now d' = 2d

⇒ R = ρl/A = 2.5 Ω