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Difficulty: EasyElectromagnetic Induction

A bar magnet is moved with its north pole approaching one end of a closed circular wire coil. According to Lenz's law, which of the following correctly describes the induced magnetic polarity at that face of the coil and the direction of the induced current as viewed from the side of the magnet?

  1. Anticlockwise current, developing a North poleAnswer
  2. B
    Clockwise current, developing a South pole
  3. C
    Clockwise current, developing a North pole
  4. D
    Anticlockwise current, developing a South pole

Answer

Anticlockwise current, developing a North pole
According to Lenz's law, an induced current flows in a direction such that its magnetic field opposes the change in magnetic flux that produced it. As the North pole of a magnet approaches the coil face, the coil must oppose this motion by establishing a North pole on that face. By the right-hand grip rule, looking at a North pole corresponds to an anticlockwise flow of current.

Step-by-Step Solution

1
Apply Lenz's law to determine the induced magnetic polarity
The near face of the coil must develop a North pole to repel the approaching North pole of the bar magnet
Lenz's law states that the direction of an induced current always opposes the magnetic flux change causing it.
2
Determine the direction of induced current corresponding to a North magnetic pole
Looking directly at a North magnetic pole, the induced current flows in an anticlockwise direction
By the right-hand rule (or N-S rule for coils), an anticlockwise current produces a magnetic field directed out of the face (North polarity).

Key Concept

Lenz's Law
Estimated Time:45s
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Topics

Electromagnetic Induction

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