wow, what a past few weeks. This has been intense, and there is still plenty more to come. This semester has been by far the most stressful and busy of my life, and i do belive the worst of has yet to rear its head. I suspect to see the ugliest of this monster next week, udring what i woudl liek to call crunch time. Due to this i have had little energy lately to partake in scoial gatherings, binge drinking, band meetings, musical discussions and all sorts of othe rfun activities. Alas, all is not lost, fo rthe gift of knowledge has been bestowed upon me these past few months, in somewhat excessive amounts. I feel somewhat overprivileged and obligated to share this gift with the rest of the world, so i am starting a series of lectures in the blog forum. I will share my veritable expertise on wave theory, electromagnetics, and circuitry with regards to their applications to our good friend rock n' roll. my first lecture will begin now, so put thAt snacK away and get out your notebook.
Have you ever wondered how an electric guitar works (or for that matter our beloved, yet slightly neglected, fender rhodes)? well i have, and it turns out to be quite interesting. With a short crash course on electromagnetics we can easily see how that simple vibrating string gets to our ear and creates that most beloved of all the arts known as music.
First we must be introduced to the concept of electric field and voltage. An electric field basically electrical energy. This energy comes from charges(otherwise known as electrons and protons). Electrons are (-) charges and protons are (+) charges. An electric field is energy that can't be felt by us in any way. Only charged particles are sensitive to electric fields. If an electric field were in front of you, pointing from let to right, and a single free electron were placed in that field, the electron would move to the lect, conversely, a single proton would move to the right.
You can think of voltage as potential energy from your most recent physics class. Voltage is, in a sense, the ability of an electric field to move a charge, it isn't the force that moves the charge, it is the energy stored in a field that could move a charge, if a charge were present.
The final concept to introduce is the magnetic field. Everyone is familiar with magnets. A magnetic field is the field of energy created by a magnet or magnetic material. There are many ways to create magnetic fields, but that isn't important for our condition.
Now, on to guitars. The two components of an electric guitar that make sound possible are the string and the pickup. Let's start with the pickup. The pick is nothing more than a magnet. It is a magnetic material wound in a metal. The number of windings and shape and size of the core can drastically effect the sound of the guitar. This is because a magnet of this structure has natural filtering abilities. Also, another way to effect the sound is with the number of magnets used in one pickup. My and bills guitars both have humbuckers, one pickup consisting of two separate magnets, each with their own windings. THis magnet sets up a magnetic field, which generally would mean nothing other athn a metal object would stick to it if brought close enough. BUt something interesting happens when a string, which sits in the magnetic field, is plucked.
Guitar stinrgs are nothing more than a strand of metal. Metals as you know are good conductors. THis means they have a large amount of electrons, (-) charges, which are free to move as they please. When the string is plucked it vibrates rapidly inside the magnetic field of the pickup. Faraday's law states that, when a free charge moves inside a magnetic field, an electric field is induced. Furthermore, this electric field is proportional to the rate of change of position of the chrage(string). Simply, this means taht the velocity of the string is proportional to teh electric field induced. But, since the string is vibrating, its velocity is always changing. It can be shown that the velocity changes in a harmonic motion (sinusoidal). What this means is that the string moves witha certain frequency, percieved by the human ear as pitch, and an electric field is induced with the same frequency.
Here is where the windings of the pick up come in. The electric field induced by the string causes a voltage across the pickup. This voltage causes the free electrons in the windings to move. The windings are connected to the cable that goes into your amp, so the electrons are moved by the fields induced around the pick up to your amp, where they are amplified and sent to your speakers. Thus the magic of the guitar is unveiled. The rhodes works in the same way, except instead of guitar strings you have metal bars, and instead of a pick there is a hammer. It seems a bit complicated, but it really is quite simple. I must say thought that les paul (the inventor of the electric guitar) was quite ingenious. Please come to me with any questions on this lecture, i would be happy to clarify anything that isn't crystal clear. The net lecture will be on waves and frwquency content.
pat
