Question

resistance of a metal wire of length 5 M is 100 ohm if the area of cross section of a wire is 3 ×10-7 m2 calculate the resistivity of a metal

Answer 1

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Here, given 

resistance = 50 Ω (R)

Length = 2 m ( l )

Diameter = 0.6 mm

∴ radius = 0.6/2 = 0.3 mm 

→ 0.3 mm =  3 x 10−⁴ m( converted to metres) 

we dun know abt resistivity,

Resistivity (ρ) =?

∴ area of cross section of wire = π r²

→ 3.14 x (3 x 10−⁴)²

→ = 2.826 x 10−⁹ m²

now, applying ρ = R X A / l

→ ρ = 50 Ω  x  2.826 x 10−⁹ m² / 2m

→ ρ  = 25 x 2.826 x 10−⁹ Ω  m

→ ρ = 70.65 x 10⁻⁹

→ ρ  = 7.065 x 10⁻⁸ Ω m

∴ resistivity ( ρ  ) = 7.065 x 10⁻⁸ Ω m

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hope it helps! ^_^ 

Answer 2

The answer is 60 x 10^-7