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JEE Main2007PhysicsMagnetic Effects of CurrentActual

A long straight wire of radius ' a ' caries a steady current i . The current is uniformly distributed across its cross section. The ratio of the magnetic field at a 2 and 2 a is

Options

  1. A1 4
  2. B4
  3. C1
  4. D1 2

Correct answer

C. 1

Step-by-step solution

B 2 a 2 = ₀ i a ^2 ( a ^2 4 ) B ₁= ₀ i 4 a (i) B ₂ 2 (2 a )= ₀ i B ₂= ₀ i 4 a (ii) B ₁ ~B ₂ =1

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