Question

The resistance of the conductor is r. if its length is doubled, then its new resistance will be (a) r (b) 2r (c) 4r (d) 8r

Answer 1

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Answer 2

answer : option (C) 4r

resistance of a conductor is

• directly proportional to its length
• inversely proportional to its cross sectional area.

when volume of conductor remains same.

R ∝ l² , R ∝ 1/A²

here question discussed about length of conductor so we have to choose R ∝ l²

i.e., R1/R2 = l1/²/l2²

⇒r/R2 = (l/2l)²

⇒R2 = 4r

hence, if the length of wire is doubled resistance of wire will be four times of its initial.

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