MUTUAL INDUCTION
Because the secondary windings are wound on the same core as the primary, the magnetic field produced by the primary winding cuts the windings of the secondary also, Figure 19–14. This continually changing magnetic field induces a voltage into the secondary winding. The ability of one coil to induce a voltage into another coil is called mutual induction. The amount of voltage induced in the secondary is determined by the number of turns of wire in the secondary as compared with
the primary. For example, assume the primary has 240 turns of wire and is connected to 120 volts AC. This gives the transformer a volts-per-turn ratio of 0.5 (120 volts per 240 turns = 0.5 volt per turn). Now assume the secondary winding contains 100 turns of wire. Because the transformer has a volts-per-turn ratio of 0.5, the secondary voltage will be 50 volts (100 X 0.5 X 50).