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Faraday's Law of Induction for Time-Varying Fields

In 1820, Oersted experimentally observed that a steady current produces a magnetic field. This experimentally led to the Biot–Savart law and Ampere’s law.

The English physicist Michael Faraday and the American scientist Joseph Henry independently and simultaneously in 1831 observed experimentally that any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be induced in the coil. No matter how the change is produced, the emf will be generated. If the circuit is a closed one, this emf will cause flow of current. This phenomenon is known as electromagnetic induction.
  1. Neumann’s Law
    When a magnetic field linked with a coil or circuit is changed in any manner, the emf induced in the circuit is proportional to the rate of change of the flux linkage with the circuit.
  2. Lenz’s Law
    The direction of the induced emf is such that it will oppose the change of flux producing it. These two laws together can be termed as Faraday’s law of electromagnetic induction.
    Statement of Faraday’s Law The emf induced in a closed circuit is proportional to the rate of change of the magnetic flux linkage and the direction of the current flow in the closed circuit is such that it opposes the change of the flux.
    Description: Description: 16980.png= Electric field
    Description: Description: 16582.png= Magnetic field
    φ= Flux linking with the circuit
    E = Induced emf in the circuit
    λ = Total flux linkage in a multiturn coil
    C = Closed circuit binding an open surface S, placed in the magnetic field

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