Electromagnetic Induction 2

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Producing A.C. Using Induction

A coil can be rotated in a magnetic field to produce alternating current (a.c).

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Faraday's Law

  • Faraday’s law says that the induced emf is directly proportional to the rate of change of flux linkage.
    • The flux linkage through the coil is BAN cosθ.
    • For this coil, θ = ωt, where ω = 2πf and f is the frequency of rotation.
    • Thus the flux linkage is BAN cos(ωt) and the emf will be directly proportional to BANω sin(ωt).
    • Finally, if f is increased, this not only increases the frequency of induced emf, it also increases the amplitude of the induced emf.

Induced Electromotive Force

When a coil is rotating in a magnetic field, the flux linkage is constantly changing. This induces an electromotive force (emf).

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A rotating coil

  • A coil is made of N turns and has an area A and is rotating at an angular velocity ω{\omega}.
  • If the coil rotates, it 'cuts' the field lines. This induces an emf.
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  • The equation for the emf induced is:
    • Emf induced = field strength x area x number of coils x angular speed x sin(ωt)sin({\omega}t)
    • emf=BANωsin(ωt)emf=BAN{\omega}sin({\omega}t)

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1Measurements & Errors

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4Mechanics & Materials


6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

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12Option: Turning Points in Physics (A2 only)

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