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Difficulty: EasyElectromagnetic Induction

A bar magnet is pulled away from a stationary circular coil such that its South pole moves directly away from the front face of the coil. Based on Lenz's law, which polarity is induced on the front face of the coil?

  1. North pole, to attract the receding South pole and oppose its motionAnswer
  2. B
    South pole, to repel the receding South pole and oppose its motion
  3. C
    South pole, to attract the receding South pole and assist its motion
  4. D
    North pole, to repel the receding South pole and assist its motion

Answer

A North pole is induced on the front face of the coil to attract the receding South pole and oppose its motion.
According to Lenz's law, the direction of induced current creates a magnetic field that opposes the change causing it. As the South pole moves away, the decreasing magnetic flux is opposed by an attractive force pulling the magnet back. Therefore, an opposite pole (North pole) is induced on the coil's front face.

Step-by-Step Solution

1
Identify the change causing electromagnetic induction
The South pole of the magnet is moving away from the coil, causing a decrease in magnetic flux through the coil.
Induction is driven by a change in magnetic flux according to Faraday's law.
2
Apply Lenz's law to determine the direction of induced magnetic effect
The induced magnetic field must attempt to pull the magnet back to oppose its withdrawal.
Lenz's law dictates that the direction of an induced current always opposes the motion or change causing it.
3
Determine the required magnetic polarity on the front face
To attract the departing South pole, an opposite magnetic pole (North pole) must be induced on the front face.
Unlike magnetic poles attract each other.

Key Concept

Lenz's Law and Direction of Induced Current
Estimated Time:45s
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Topics

Electromagnetic Induction

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