HOW IT WORKS

All metals contain a movable substance called "electric charge". Even uncharged wires are full of charge! After all, the atoms of the metal are made half of positively-charged protons, and half of negative electrons. Metals are special because their electrons don't stay connected to the metal atoms, instead they constantly fly around inside the metal and form a type of electric "liquid" inside the wires. All wires are full of electric fluid. Modern scientists call this liquid by the name "electron sea" or "electron gas," or the "sea of charge." The fluid charge is movable, and this lets metals be electric conductors. The movable charge-stuff is not invisible, it actually gives metals their silvery shine. The electron gas is like a silvery fluid. Sort of.

Whenever a circle of wire surrounds a magnetic field, and if the magnetic field then changes, a circular "pressure" called Voltage appears. The faster the magnetic field changes, the larger the voltage becomes. This circular voltage trys to force the movable charges inside the wire to rotate around the circle. In other words, moving magnets cause changing magnetic fields which try to create electric currents in closed circles of wire. A moving magnet causes a pumping action. If the circuit is not complete, if there is a break, then the pumping force will cause no charge flow. Instead, a voltage difference will appear at the ends of the wir es. But if the circuit is "complete" or "closed", then the magnet's pumping action can force the electrons of the coil to begin flowing. A moving magnet can create an electric current in a closed circuit. The effect is called Electromagnetic Induction. This is a basic law of physics, and it is used by all coil/magnet electric generators.

Generators don't have just one circle of wire. Suppose that many metal circles surround the moving magnet. Suppose that all the circles are connected in series to form a coil. The small voltage from each circle will add together to give much larger voltage. A coil with 100 turns will have a hundred times more voltage than a one-turn coil.

Now for the light bulb. If we connect the ends of the coil together, then whenever the magnet moves, the metal's charges will move and a large electric current will appear in the coil. What if we instead connect a light bulb between the ends of the coil? A light bulb is really just a piece of wire. The charges of the light bulb's filament will be pushed along. When the charges within the copper wire pass into the thin light bulb filament, their speed greatly increases. When the charges leave the filament and move back into the larger copper wire, they slow down again. Inside the narrow filament, the fast-moving charges heat the metal by a sort of electrical "friction". The metal filament gets so hot that it glows. The moving charges also heat the wires of the generator a bit, but since the generator wires are so much thicker, almost all of the heating takes place in the light bulb filament.

So, just connect a light bulb to a coil of wire, place a short powerful magnet in the coil, then spin the magnet fast. The faster you spin the magnet, the higher the voltage pump-force becomes, and the brighter the light bulb lights up. The more powerful your magnet, the higher the voltage and the brighter the bulb. And the more circles of wire in your coil, the higher the voltage and the brighter the bulb.

OTHER THINGS TO TRY

Disconnect one wire from the light bulb. Spin the magnet. While still spinning the magnet, have a friend touch the wires together so the bulb lights up again. Is the nail still easy to spin? Keep spinning the magnet while your friend connects and disconnects the bulb. Feel any differences in how hard you must spin the nail? Also try spinning the magnets while your friend connects the generator wires directly together (with no bulb connected.)

SO WHAT?

Think of it like this. If you rub your hands together lightly, the skin stays cool, but if you rub your hands together hard, your skin gets hot. It takes more effort to rub skin hard so that it heats up; it takes work. And in a similar way, it's hard to heat the lightbulb filament, it takes work. You twist the generator shaft, the generator pushes the wire's charge through the tiny filament, and if you don't keep spinning the magnet, the magnet will be slowed quickly.

FEEL THE ELECTRONS

TURN OFF THE FIELD

MEASURE THE VOLTAGE AND CURRENT

How high can you make the voltage just by using fingers? Or using a hand drill? Try spinning the magnets just fast enough to barely light the bulb in a dark room. How small a voltage is needed? Also try disconnecting the light bulb, then measure the AC voltage across the two ends of the coil. Can you tell if it's still the same as when the bulb was connected? Hint: to spin the magnets at a constant rate, use an electric drill with a fully-charged battery. Or perhaps hook the nail to an electric motor and connect the motor to a DC power supply with settable voltage.

Note: The light bulb has around 50 ohms resistance. Also, 250ft of #30 wire has around 21 Ohms resistance. Because of the wire resistance, the generator can only create around 60 milliamps current at most (0.06 amperes.) If you wind extra #30 wire onto the generator, it will increase the maximum voltage, and maximum power. But since this adds more resistance it WON'T increase the maximum possible current. To increase the maximum possible current, either replace the #30 wire with thicker wire, spin the magnets faster, or use a stronger type of magnet material.

MAKING DC

Converting to DC:

The hard way: add a spinning "commutator" switch and sliding metal "brushes," so that each time the magnets turn half way, the switch reverses the generator connections.

Easy way: Add a one-way valve! An "electricity valve" is called a diode or rectifier. If you connect a diode in series with one of your motor wires, it will only let the charges flow in one direction. It will change the Alternating Current into one-way flow (called "pulsating direct current.) Try diodes from Radio Shack such as 1N4000 or 1N4001. Unfortunately a diode needs about 3/4 volts to force any charges through, and this voltage subtracts from your generator output. If your generator only puts out one volt, then the diode will reduce this to 1/4 volt. So if you want to add a diode, try doubling or tripling the amount of wire on your generator. Also try using a special "Schottky" diode with lower voltage than 0.7V, such as 1N5819 from digikey.com

HISTORY OF "ULTRA SIMPLE" GENERATOR

Around 1994 I was thinking about the ultra-simple electric motor which later became known on internet as the "Beakman Motor." Wouldn't it be cool if kids could also make an electric generator that simple? But it should be possible with parts from a Radio Shack store, since Radio Shack had the special light bulb as well as magnets and spools of electromagnet wire. After a few hours of experimenting I fould that I could just barely light up the 20 milliamps bulb by using a single spool of #30 wire from radio shack. But the wire had to be VERY close to a fast spinning magnet, and the magnet had to be composed of four powerful ceramic magnets in a stack.

To impress all the Physics Teachers, I tried to make the parts be easily available, and the cost as low as possible. To make a popular project, I made sure no tools were needed except scissors. I refused to use ball bearings or plastic parts. So I made my own cardboard box for the coil, and used a nail for the spinning shaft. To avoid extra parts, the nail is just clamped by the powerful magnets. Here's a challenge: try to light a bulb, but do it with a generator which is even simpler.

MAGNET WARNING

(PREV: CONSTRUCTION)