Question

If a length of the wire is 50 cm and radius 0.5 mm find the resistivity of wire if its resistance is 30 ohms.

Answer 1

So easy question. I am not gonna tel you the answer but I shall provide you steps.
l=50cm=0.5m
r=0.5mm=5×10^-5m
R=30 ohm.

resistivity= RA/l
where A=
$\pi \: {r}^{2}$

Answer 2

Given :

Length = 50 cm or 0.5 m .

Resistance = 30 Ω

Radius = 0.5 mm or 0.5 × 10⁻³ m

To find: We have to find the resistivity of material in the given question.

We would first find the area of wire,

                      ∴ Area = π r²

Area of wire  = 3.14 × 0.5 × 10⁻³ × 0.5 × 10⁻³ m²

                      = 0.785 × 10⁻⁶ m²

It is given that, Length of conducting wire is 0.5 Ωm

Now, putting the values in the formula of resistivity:

Resistivity = Resistance  ×  Area  / Length

                    ρ = R × A / L

ρ = 30 ×  0.785 × 10⁻⁶ / 0.5 Ω m

ρ  = 47.1  × 10⁻⁶  Ω m

ρ  = 4.71  × 10⁻⁵  Ω m

Therefore, resistivity of wire is 4.71 × 10⁻⁵ Ω m.