Question

Calculate the resistivity of the material of wire 1.0 metre long 0.4 mm in diameter and having a resistance of 2.0 ohm

Answer 1

Numerical

Given Data:

length = 1m

diameter = 0.4mm = 0.0004 m

resistance = 2 ohms

To find:

Resistivity = ?

Formula:

R= p (L/A)

p = (RA)/L (formula where p is resistivity)

Solution:

Area = ?

Area of Wire =

$\pi \:{ r}^{2}$

radius = r = Diameter / 2

r = (0.0004) / 2 meters

r = 0.0002 m

Put into formula

Area = 3.14 * (0.0002 m)²

Area = 0.00000125 m²

Put into formula of Resistivity

p = (2 ohms x 0.00000125 m²) / 1m

p = 0.0000025 Ohmmeter

In Scientific Notation

p = 2.5x10^-6