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JEE Main2013PhysicsMagnetic Effects of CurrentActual

An electric current is flowing through a circular coil of radius R . The ratio of the magnetic field at the centre of the coil and that at a distance 2 2 R from the centre of the coil and on its axis is :

Options

  1. A2 2
  2. B27
  3. C36
  4. D8

Correct answer

B. 27

Step-by-step solution

Given : Radius =R Distance x =2 2 R aligned B_ centre B_ axis & = (1+ x^2 R^2 )^ 3 / 2 = (1+ (2 2 R)^2 R^2 )^ 3 / 2 & =(9)^ 3 / 2 =27 aligned

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