Question

resistance of a metal wire of length 5 M is 100 ohm if the area of cross section of the wire is 3 into 10 raise to minus 7 M equal calculate the resistivity of the metal

Answer 1

Resistance (R) = 50 Ω

Length of the wire ( l ) = 2 m

Diameter of the wire = 0.6 mm

Radius = 0.6 / 2 = 0.3 mm
= 3 × 10^-4 m

Resistivity ( ρ ) = ?

Area of cross sectional area of wire (A) = πr^2
= 3.14 ×( 3 × 10^-4)^2
= 2.826 × 10^9 m^2

We know,

ρ = RA / l

ρ = 50 × 2.826 × 10^-9 / 2

ρ = 25 × 2.826 × 10^-9

ρ = 70.65 × 10^-9 or 7.065 × 10^-8 Ω m

Resistivity of the wire is 7.065 × 10^-8 Ω m.

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Answer 2

Apply the formula : Resistivity = ( Resistance × area )/ length

Ans: 6× 10^-6 ohm/m