AC Generation

Electromagnetic Induction

What is this electromagnetic induction of which you speak?

Electromagnetic induction is when a voltage is created by passing a conductor through a magnetic field.

Figure 45. Magnetic poles and induction

The size of the voltage can be varied by three factors:

  1. The size of the magnetic field.  The more flux lines there are, the more flux lines there are for the conductor to cut.  The strength of flux is directly proportional to the induced voltage.
  2. The active length of the conductor.  Active length meaning the part of the conductor that actually passes through the field.  The active length is directly proportional to the induced voltage.
  3. The speed at which the conductor passes through the field.  The faster the conductor passed through the field, the greater the voltage induced.  The speed is directly proportional to the induced voltage.

These relationships to voltage can be broken into this formula:  e = βlv.


e = peak voltage induced in the inductor (volts)

B = field strength between the poles (Tesla)

l = active length of conductor (meters)

v = velocity of the conductor through the field (m/sec)

Here is an example.

A conductor that has an active length of 4 meters passes through a field of 5 Tesla at a speed of 15 meters per second.  Determine the peak voltage induced on this conductor.

(4 m)(5 T)(15 m/sec) = 300 volts peak

That’s crazy!  Who discovered that?

The discovery of electromagnetic induction is attributed to Michael Faraday who discovered that when he passed a magnetic field through a conductor a current would flow.

As long as there was motion between the field and the conductor, a voltage could be induced.  This could mean the conductor passes through a field or a field passed through a conductor.

Next up:  The alternator

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