Electricity and Magnetism

AM Radio

This exhibit demonstrates the basic elements of an AM radio: antenna, tuner, rectifier, and speaker. A long white antenna wire drops down from the roof of the exhibition hall to the exhibit. Visitors can turn a knob and adjust the position of the plates of the capacitor, adjusting the resonant frequency of the "tuner" to that of a local AM radio station. Visitors are often surprised when they notice that the power for the sound is picked up by the antenna from the power broadcast by the radio station.