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JEE Main 2023 · 25 Jan · Shift 2

JEE Main 2023 Physics question on Current Electricity

The resistance of a wire is 5 Ω5\ \Omega. Its new resistance in ohm if stretched to 5 times of its original length will be:
  1. A.
    5
  2. B.
    625
  3. C.
    125
  4. D.
    25
Show answer and solution

Correct option: C

Solution

When a wire is stretched to 5 times its original length, its volume remains constant, so the cross-sectional area becomes A/5. Since R = ρL/A, the new resistance scales as (Lnew/Lold) × (Aold/Anew) = 5 × 5 = 25 times the original. Therefore Rnew = 5 × 25 = 125 Ω.

[JEE Main 2023 · 25 Jan · Shift 2]

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