Examkin

Question

Difficulty: EasyElectromagnetic Induction

According to Lenz's law, what occurs at the near face of a stationary solenoid when the north pole of a bar magnet is moved rapidly towards it?

  1. A magnetic north pole is induced at the near face to oppose the approaching magnet.Answer
  2. B
    A magnetic south pole is induced at the near face to attract the approaching magnet.
  3. C
    A magnetic south pole is induced at the near face to repel the approaching magnet.
  4. D
    No magnetic polarity is produced because induction generates only electric voltage without magnetic fields.

Answer

A magnetic north pole is induced at the near face to oppose the approaching magnet.
Lenz's law states that the direction of an induced current is always such that its magnetic effect opposes the motion or change causing it. When a north pole approaches the solenoid face, the induced current flows counter-clockwise (viewed from the magnet) to form an induced magnetic north pole at that face, thereby exerting a repulsive force that opposes the motion.

Step-by-Step Solution

1
Identify the cause of change in magnetic flux.
The approaching north pole increases magnetic flux linking the solenoid.
Electromagnetic induction occurs whenever magnetic flux linked with a conductor changes.
2
Apply Lenz's law to determine the polarity of the induced field.
The induced current must produce a magnetic field that opposes the increase in flux caused by the approaching north pole.
Lenz's law states that the induced effect always opposes the cause producing it.
3
Deduce the required magnetic pole at the near face.
A north pole must be set up at the near face because like magnetic poles repel each other, opposing the inward motion.
Repulsion between like poles (North against North) exerts a retarding force on the approaching magnet.

Key Concept

Lenz's Law of Electromagnetic Induction
Rate this question

Topics

Electromagnetic Induction

More questions from this topic