Chapter 2-1 : Generation of Alternating Voltages
- An Alternating Voltage is one whose value varies with time in a periodic manner and whose polarity is changing at a specific frequency.
- Faraday discovered that the voltage induced in the winding of a coil located in
a magnetic field was directly proportional to the number of windings and to the time rate of change
of the amount of magnetic flux, (lines of force
) threading the coil.
with
= voltage,
= number of turns,
= lines of force,
and 
= time.- Related to this is Lenz's Law which states that the polarity of the voltage will produce a current that opposes the change in the magnetic field causing the voltage.
- Changing flux through a coil is generated by rotating the magnetic field, through the action of rotating the rotor.
- The magnetic field has north and south polarity. As it rotates its lines of magnetic flux cut across the stator coil and the polarity of the generated voltage will periodically change with the revolution of the rotor. This creates a periodic alternating voltage.
- The optimal resulting waveform is sinusoidal. This is controlled through the design of the rotor and stator and the layout of the coils.