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The strength of the magnetic field at a point r near a long straight current-carrying wire is B . The field at a distance r 2 will be

Options

  1. AB 2
  2. BB 4
  3. C2 B
  4. D4 B

Correct answer

C. 2 B

Step-by-step solution

B ∝ 1 r ⇒ B 1 B 2 = r 2 r 1 ⇒ B B 2 = r 2 r ⇒ B 2 = 2 B

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