Many objects around you contain electromagnets. They are found in electric motors and loudspeakers. Electric bells like the ones used in most schools also contain an electromagnet. The slideshow ...

THE electromagnet designed for the use of oculists by Dr. Haab, director of the Zurich eye clinic, and shown in the accompanying photographs, is the most powerful and efficient apparatus of this ...

which is effectively a fancy electromagnet—and demonstrates how it creates sound waves in this way. Finally, the fourth station demonstrates the use of a microphone to record a voice ...