Question

Calculate the length of wire of radius 0.5 mm needed to prepare a coil of resistance 12 ohms the resistivity of material of the wire is 3.14 into 10 raise to minus 3 m ohms metre

Answer 1

Given,

Radius of the wire, r= 0.5 mm= 0.5×10⁻³m

Resistance R= 12Ω

Resistivity, ρ= 3.14×10⁻³Ωm

We know that, R=ρ(l/A)

    l=RA/ρ

     =(12×πr²)/ρ

     ={12×34.14×(0.5×10⁻³)²}/(3.14×10⁻³)

    = 3 m