phoglite

Ford did it back in the 70's. See link: http://www.sivakrishna.com/stfaq.html

Here's how I understand it... maybe it will help. 1.) Magnetic fields and electrons have a special relationship. A moving electron creates a magetic field and moving a magnetic field can push or move an electron. For example - you have a piece of conductive wire which has lots of electrons (all atoms have electrons) and move a magnet over it - electrons get pushed along the wire (this is how a generator works to make electricity). You can reverse this by running electric current through a wire (electrons flowing) and it will create a magnetic field that can push a magnet (this is how motors work). 2.) DC current involves pushing the electrons along the wire continuously... while AC (alternating current) involves pushing the electrons a little bit and then jerking them back the other direction - over and over. This back and forth action can usually be measured in number of cycles per second or the frequency - hertz. 3.) This frequency can vary and depends on what is moving those electrons back and forth (all the while shifting the magnetic field it generates back and forth). This frequency is how you would categorize the particular place on the EM spectrum that you're trying to relate to. Household AC current might be at 60 hz because the electrons flowing into any AC device are moving back and forth 60 times per second, while generating a corresponding disturbance in the electromagnetic field. Organic or "natural" sources of EM fields are likely continuously changing the frequency at which they move their electrons around so it's hard to say where they would fit in a chart since they may move all over the thing. Hope that helps! -phog