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MHT CET2018PhysicsCurrent Electricity

A conducting wire has length L 1 and diameter d 1 . After stretching the same wire length becomes L 2 and diameter d 2 . The ratio of resistance before and after strectching is

Options

  1. Ad 2 4 : d 1 4
  2. Bd 1 4 : d 2 4
  3. Cd 2 2 : d 1 2
  4. Dd 1 2 : d 2 2

Correct answer

A. d 2 4 : d 1 4

Step-by-step solution

R 1 R 2 = L 1 L 2 × A 2 A 1 = L 1 L 2 × π d 2 2 4 π d 1 2 4 ...(1) L 1 d 1 2 = L 2 d 2 2 ...(2) L 1 L 2 = d 2 d 1 2 R 1 R 2 = L 1 L 2 × d 2 d 1 2 = d 2 4 d 1 4

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