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Let’s Talk About Electricity and Magnets First This stuff is basic to any kind of electrical charging system, so you should understand this first. The only test will be if you know enough to do what you want to do without messing anything up. When you put electricity (current) down a wire, the wire will have a magnetic field around it. Conversely, if you move a wire through a magnetic field, a small current (electricity) is created in the wire. The more wires you use and/or the greater the strength of the magnetic field, the greater the effect becomes. These two inverse principles are the basis for electric motors, generators, alternators, and even things like the solenoid inside of a relay. If you have one item (movement or electricity), you can convert it into the other. Also tied in here is the fact that magnets repel and attract each other – that's part of how you make an electric motor move. You can use more turns of wire (windings) to generate a stronger effect. What about voltage vs. current? Well, current is a measure of how much stuff is flowing down a wire – sort of like the number of gallons of water that are flowing down a pipe every second. Voltage is a measure of pressure – like how many pounds per square inch (PSI) of air are in your tires. They measure different things, but they can be confusing since you can't "see" electricity. What about AC vs. DC? These stand for Alternating Current and Direct Current, respectively. AC is the stuff used in your house. DC is the stuff used in your car and what you get out of a battery. The difference is that in DC current always flows in the same direction – from positive to negative (or, if you're a real physics geek, from negative to positive) – while AC alternates the flow of current between the two directions at some rate. This rate is expressed a cycles per second, or Hz (pronounced "hurtz"). In the USA, the electricity in your house is changing directions at 60Hz (or 60 times a second). The final tid-bit of information is that when you spin wires and magnets near each other, you create AC in the wire. This is because the wire and magnets are continuously moving closer to and farther away from each other in a repeated cycle. As they move closer together, the current moves one way. As they more farther apart, the current goes the other way. If you've ever seen the typical "sine wave" graph of AC power, that exactly what we’re talking about here. This is important be- cause you need some way to make that AC into DC to use it in your car. The process of changing AC into DC is called rectification. The method used to do that is the key design difference between an alternator and a generator.