Question

Resistance of a metal wire of length 2m is 30 ohms at temperature 25oc, if diameter of the wire is 0.6mm, then what will be the resistivity of the metal at that temperature?

Answer 1

Given

Length of the wire L= 2 m

Resistance of the wire R = 30Ω  

Diameter of the wire d = 0.6 mm

radius of the wire r = 0.3 mm = 0.3 ×10⁻³ m  

And temperature T= 25⁰C (Room temperature)

We know resistance R = (ρL)/A

ρ = (RA)/L

ρ = [30×3.14×(0.5×10⁻³)²]/2 = 4.239 × 10⁻⁶ Ω m