Induced EMF and Lenz’s law - Electromagnetic Induction

Induced EMF and Lenz’s law



In this lesson, we will learn:

  • A changing magnetic field induces current
  • Direction of the induced current depends on the direction of the motion of the magnet with respect to the coil.
  • No current is induced if the magnet does not move relative to the coil.
  • It is the relative motion between the magnet and coil that counts.
  • Lenz’s law


Induced EMF
  • The purpose of this concept is to produce an electric current from a magnetic field.
  • A coil of wire, XX, is connected to a battery. A magnetic field is produced by the current that flows through the coiled wire XX and is intensified by the iron core.
  • The current in the second coiled wire, YY, is the result of change in magnetic field. The current is detected by the galvanometer only when switch is closed or opened.
  • Constant current in XX produced constant magnetic field, which produces NO current, but changing the magnetic filed can produce an electric current in coil YY.
  • Such current is called the induced current. Changing magnetic field through coil YY, produces an electric current in the coil.

  • a changing magnetic field NOT the magnetic field itself, induces an emf”

Induced emf and Lenz's law

The relative motion between magnet and coil induces the current

Lenz’s law;
A current produced by an induced emf moves in a direction so that its magnetic field opposes the original change in flux.

  • Magnet is pushed into the coil

  • Induced emf and Lenz's law

  • Magnet is pulled out of the coil

  • Induced emf and Lenz's law

  • Stationary magnet

  • Induced emf and Lenz's law
  • Intro Lesson
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Induced EMF and Lenz’s law

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