Question

(b) The length of a conducting wire is 60 cm and radius is 0.5 mm. Calculate the resistivity if the
resistance is 20 ohm
Ans.​

Answer 1

Explanation:

Given, Diameter=0.5mm,resistivity=1.6×10

−8

Ω−m,resistance=10Ω

we know that R=ρ

A

1

⇒1= i

ρ

RA

Where A is the area of the cross-section,

=

1.6×10

−8

10×3.14×(

2

0.0005

)

2

=122.7m

Answer 2

Given:

Length of the wire = 60 cm = 0.6 m

Radius of the wire = 0.5 mm = 5 × 10⁻⁴ m

Resistance = 20Ω m

↦ Now resistivity is given by,

  R = ρ L/A

   where R = resistance

               ρ = resistivity

               L = length of conductor

               A = area of cross section

↦ Substituting the data,

    20 = ρ × 0.6/ 7.85 × 10⁻⁷

    764331.2 ρ = 20

    ρ = 20/764331.2

    ρ = 2.61 × 10⁻⁵ Ω m