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Concepts Of Physics MCQ Edition [Volume 2]PhysicsPermanent Magnets

If a current in a circular loop is equivalently substituted by a magnetic dipole,

Options

  1. Athe distance d separating the poles is constant
  2. Bthe product m d is constant
  3. Cthe pole strength m for each pole is constant
  4. Dthe ratio m d is constant

Correct answer

B. the product m d is constant

Step-by-step solution

The magnetic moment of a circular loop carrying current I and having area A is given by M = IA . When this loop is equivalently substituted by a magnetic dipole with pole strength m and separation distance d , its magnetic moment is given by M = md . Equating the two expressions for magnetic moment, we get md = IA . For a given current loop, the current I and area A are constant. Therefore, the product md must be constant.

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