EM.3(1) - THE SMALL TRANSFORMER

It consists of a rectangular iron core, standing 15 cm tall. The primary coil has a fixed number of turns and is connected to an AC power supply. The iron core has its top side hinged allowing the secondary coil to be easily changed: one can vary the number of turns, connect the coil to a small lamp, to an oscilloscope or, to a multimeter. For example, two resistors of different values can be connected around one side of the iron core and the differece in voltage across them measured.

Primary coil has 490 turns, and the secondary has 35.

EM.3(2) - INDUCTION COIL TRANSFORMER

The same induction coil used for the "Jumping Ring" and "Submerged Lamp" demonstrations is used here to show the principles of a transformer. A long wire is used as the secondary coil and is connected to the large lecture oscilloscope. As one changes the number of turns around the iron core, the amplitude of the voltage displayed on the oscilloscope increases.

EM.3(3) - TESLA COIL

The Tesla coil is an air-core transformer with primary and secondary coils tuned to resonate. The primary and secondary coils function as a step-up transformer which converts a relatively low-voltage high-current signal to a high-voltage low-current signal at high frequencies. It demonstrates the fundamental principles of high frequency elecrical phenomena. It illustrates the principles of the ionization of gases and the behavior of insulators and conductors when in contaact with high frequency electrical fields. There are more than a dozen demonstartions that can be perfomed with this Tesla coil.

The Tesla coil was developed by Nikola Tesla to transmit electrical power without wires. An antenna would be used to pull the transmitted electrical energy into the electrical system. It can be considered a simple radio transmitter, operating within a broad range of high frequencies, which transmits power rather than information.

EM.3(4) - MUTUAL INDUCTION OF A TRANSFORMER

A 1:1 transformer has its primary coil connected to a light bulb and an alternating power supply while its secondary is connected to a switch and another light bulb. When the switch is open neither bulb lights. Now the secondary circuit is drawing current, so the mutual inductance of the two coils reduces the effective inductive reactance of the primary circuit to light its bulb.