Question

A manganin wire of length 2m has a diameter of 0.4 mm with a resistance of 70 Ω. Find the resistivity of the material.

Answer 1

Given conditions ⇒

Length of the wire(l) = 2 m. 

Radius of the cross-section(r) = 0.4 mm.
 = 4 × 10⁻²m. 

∴ Area of the croos-section = πr²
  = 22/7 × (4 × 10⁻²)²
  = 22/7 × 16 × 10⁻⁴
 = 50.28 × 10⁻⁴ m²

Resistance (R) = 70 Ω

Using the Formula,
   ρ = Ra/l
   = 70 × 50.28/2
   = 1760 Ω-m.


Hence, the Resistivity of the Managanin wire is 1760 Ω-m. 


Hope it helps.