I’ve realized that when friends of mine use gadgets like cell phones, computers, or even air conditioning, they rarely ever feel the need to discover for themselves the intrigue behind those processes. They tell me, “I don’t care how it works or what makes it work. I just care that it works.” Perhaps I’m in a minority, but I’m fascinated by the scientific principles behind many of the technological gadgets that we use. We press ‘on’ and the thing just works. Almost like magic.
As an avid guitarist, I have long been intrigued by the method through which the string vibrations on my electric guitar are transduced into sound that emit from an amplifier. Naturally, I think this is a topic worth investigating. So how in fact does this process work?
Guitars can have different types and different set-ups of pick-ups, but for simplicity’s sake we’ll focus on the basic concept. Pick-ups are based upon the concept of electromagnetic induction. What does that mean? It is the creation of an electromotive force, also known as voltage, due to its dynamic interaction with a magnetic field.
The pick-up has a permanent magnet which is wrapped in a copper coil. So in this scenario, the magnet passing through the coil will induce voltage in the coil. How? Well, the magnet creates a magnetic field, and the motion of the vibrating steel strings disturbs that field. This causes a change in the magnetic flux (the amount of magnetic field per area per time), which induces a voltage in the coil. It is this signal which is sent to the amplifier. If you’re new to physics and Faraday’s Law of Induction, then the basic take-away point is the following: A magnet passing through a coil of wire will induce an electromotive force in the coil, which causes a flow of current (flow of electric charge).
There! And so the next time you hear your favorite guitar hero slicing and dicing it up on the electric guitar, you’ll be able to bore your friends and let them know the scientific principle at play!