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in Physics by (44.7k points)

A wire has resistance Ro, What will its resistance if it is stretched to double? 

(A) 4 Ro 

(B) 3 Ro 

(C) Ro 

(D) 2 Ro

1 Answer

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Best answer

The correct option is  (A) 4 Ro.

Explanation:

We know R = (ρℓ / A) if wire is stretched to double then ℓ' = 2ℓ and to keep volume constant area will be half A' = (A/2) 

∴ R' = [{ρ(2ℓ)} / (A/2)] = [(4ρℓ) / A] = 4R 

Hence R = R0 

∴ R' = 4R0

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