Table of Contents
Electric Monochord
Requirements
- Electric monochord (built)
- Amplifier
- Oscilloscope
Description
This demo serves to illustrate both the principle of electromagnetic induction as well as how it is something with which all of us have experience through music. The electric monochord is essentially a one stringed analogue of an electric guitar. It consists of a ferromagnetic string of adjustable tension, a magnet placed underneath the string that slightly magnetizes it, and a ~8500 turn coil wound around the magnet and connected to a BNC plug that allows us to measure the voltage drop across it. When the string is plucked, the magnetic field above the coil will oscillate at the same frequency as that of the string due to the string's magnetization caused by the magnet underneath it. From Faraday's Law, this will produce an oscillating EMF across the coil. This EMF can be measured using an oscilloscope, or heard through the amplifier.
Location: J3, same as the coupled oscillating magnets.
Special precautions
None, same precautions one would take with an electric guitar.
Other ideas
This demonstration can be presented in conjunction with the “Coupled Oscillating Magnets” demonstration, since they essentially demonstrate the same principle: mechanical oscillations converted into electromagnetic oscillations due to Faraday's law of induction.