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AIIMS2018PhysicsMagnetic Effects of Current

Assertion : When radius of a circular loop carrying current is doubled, its magnetic moment becomes four times. Reason : Magnetic moment depends on area of the loop.

Options

  1. AIf both assertion and reason are true and reason is the correct explanation of assertion.
  2. BIf both assertion and reason are true but reason is not the correct explanation of assertion.
  3. CIf assertion is true but reason is false.
  4. DIf both assertion and reason are false.

Correct answer

A. If both assertion and reason are true and reason is the correct explanation of assertion.

Step-by-step solution

Magnetic dipole moment of the current loop = Ampere turns Area of the coil or M=N I r^2 When radius of the coil becomes double, new magnetic moment will be M₁=N I (2 r)^2=4 N I r^2=4 M Hence magnetic moment becomes four times when radius is doubled.

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