Question

the restivity of copper
is 1.7x10^-8
ohmmeter what
length of a copper wire
of diameter 0.1mm will have a resistance of 34 ohm... step by step.. ​

Answer 1

Answer:

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Explanation:

Resistance of a wire is given as,

R = ρL/A

where,

ρ = resistivity = 1.7 x 10⁻⁸

L = length

A = area

= πr²

= π(0.05 x 10⁻³)²

= 25π x 10⁻¹⁰ m²

i) Given R = 34

=> ρL/A = 34

=> (1.7 x 10⁻⁸ x L)/25π x 10⁻¹⁰ = 34

=> L = 34 x 25π x 10⁻²/1.7

=> L = 5π = 15.7 meters

Hence the length of the wire should be 15.7 meters.

ii) since R = ρL/A

and A = πd²/4

=> R ∝ 1/d₂

=> R₂/R₁ = (d₁/d₂)²

=> R₂/R₁ = 2² = 4

Hence R₂ : R₁ = 4 : 1