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JEE Main · 2023 · 25 Jan 2023 · Shift 2 · Current Electricity

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The resistance of a wire is . It's new resistance in ohm if stretched to 5 times of it's original length will be :
  1. (A)625
  2. (B)5
  3. (C)125✓ Correct
  4. (D)25

Answer: (C)

Solution

Stretching keeps the volume fixed, so making the wire five times as long thins it to one-fifth of its area. Since , the longer length and the smaller area together raise the resistance by a factor . The stretched wire has resistance .

JEE Main · 2023 · 25 Jan 2023 · Shift 2 · Single correct option

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