HOW IT WORKS All metals contain a movable substance called "electric charge". Even uncharged wi res are full of charge! After all, the atoms of the metal are made half of positive protons and half of negative electrons. Metals are special because their electrons don't stay connected to the metal atoms, instead they fly around inside the metal and form a type of electric "liquid" inside the wi res. All wi res are full of electric fluid. Modern scientists call this the "electron sea" or "electron gas." 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.

When a circle of wi re surrounds a magnetic field, and 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 in the wi re to rotate around the circle. In other words, moving magnets cause changing magnetic fields which try to create electric currents in closed circles of wi re. A moving magnet causes a pumping action along the wire. If the circuit is not complete, if there is a break, then the pumping force won't cause any 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 w ire. Suppose that many circles surround the moving magnet. Suppose that all the circles are connected in series to form a coil. The small voltages from all the circles 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.

Why is this generator AC and not DC? When the magnets flip, they create a pulse of voltage and current. But when they flip a second time, they create an opposite pulse? Yes. So then a spinning magnet is making electric signals that go plus-minus-plus-minus? Yep. It happens because, in order to create voltage and current, a magnet pole must sweep sideways across a wire. If it sweeps along a wire, nothing happens. In our little generator here, the magnet poles don't sweep constantly along the curve of the wire. Instead, first the north magnet pole sweeps across one side of the coil, and at the same time the south magnet pole sweeps backwards across the other side. The two effects add together. But next, the magnet keeps turning around, and now the opposite poles sweep across those parts of the coil. The magnet has flipped, the magnet poles are reversed, so the coil's voltage will be backwards. And if a bulb is connected, then any current will be backwards too. Each time the magnet makes one complete turn, it creates a forward pulse and then a backwards pulse. Spin the magnet fast, and it makes an alternating wave: AC.

If you want a DC generator, you'll have to add a special reversing switch to the magnet shaft. It's a switch called a "commutator." If you look up some DC generator DIY projects, you'll see how to built the commutator switch. But those generators aren't Ultra Simple!

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. The coil gets slightly warm. What if we instead connect a light bulb between the ends of the coil? A light bulb is really just a piece of thin wire. The charges of the light bulb's filament will be pushed along. When the charges within the copper wi re pass into the thin light bulb filament, their speed greatly increases. When the charges leave the filament and move back into the larger copper wi re, 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 wi res of the generator a bit, but since the generator wi res are so much thicker, and since the bulb's thin filament is slowing the current throughout the entire coil, 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 flip 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. In theory you should be able to light up a normal 3V flashlight bulb, but only if you can spin your magnets inhumanly fast. OTHER THINGS TO TRY Disconnect one wi re from the light bulb. Spin the magnet. While still spinning the magnet, have a friend touch the wi res together so the bulb lights up again. Is the nail still as easy to spin? Keep spinning the magnet while your friend connects and disconnects the bulb. Do you feel any differences in how hard you must spin the nail? Also try spinning the magnets while your friend connects the generator wi res directly together (with no bulb connected.)

SO WHAT? When you crank the generator and make the lightbulb turn on, you are working against electrical friction in order to create the heat and light. You can FEEL the work you perform, because whenever you connect the bulb, it suddenly gets harder to crank the generator. When you disconnect the bulb, it gets easier.

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 wi re's charge through the tiny filament, and if you don't keep spinning the magnet, the magnet will be slowed quickly.

FEEL THE ELECTRONS When your hand spins the magnet, you can feel the extra work it takes to light the bulb. This happens because your hand is connected to the flowing charge in the bulb, and when you push on it, you can feel it push back on you! How is your hand connected to the flowing charges? Your hand twists the nail, the nail spins the magnet, the magnet pushes the invisible magnetic fields, the fields push the movable charges, the charges flow slowly through the light bulb filament, and the tiny filament causes friction against the flow of charge and heats up. But then the reverse happens! The charge can't move much because of the tiny filament, so it resists the pressure from the magnetic fields, which in turn resist the pressure from the magnet, which resists the twisting pressure from the nail, which resists the twisting pressure from your fingers. So, in a very real way, you can FEEL the electrons in the light bulb filament. When you push them, you can FEEL their reluctance to move through the narrow filament!

TURN OFF THE FIELD Try changing the magnets' position. Remove the magnets, then tape them around the nail so that the two stacks are clinging side by side, rather than stacked up in a line. Spin the magnets. Does the light bulb still light up? No. This happens because The N pole of one magnet stack is very close to the S pole of the other, and vice versa. The magnetic field is now stretching between the two stacks of magnets, and isn't spreading outward. Most of the field is trapped between the neighboring opposite poles, so the field doesn't extend out through the coil. When magnets are side by side like this, they form one larger but weak magnet. On the other hand, when you make a single stack of magnets instead, the field extends outwards for many inches. The stacked magnets form a larger but very strong magnet. If you spin the single magnet stack, the field cuts through the wi res and pumps their electrons into motion.

MEASURE THE VOLTAGE AND CURRENT If you can get a cheap Digital Voltmeter or DVM from Harbor Freight Tools, you can make some measurements. (Once you can see some numbers, you can perform some professional science experiments. This is great for science fair projects.) Spin the magnets to light up the bulb, then connect the meter leads across the light bulb connections. Set the meter for AC volts. Spin the magnets and see just how high a voltage your generator produces.

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 spin the magnets much faster, replace the #30 wire with thicker wire, or use a stronger type of magnet material.

MOTOR CHALLENGE! There is a simple way to convert your generator into a motor. It involves using paint or tape to insulate a spot on one side of the nail, then using a 6V battery and using the generator's wi res, touching the nail to form a switch. The rotating magnets turn the nail, which turns the coil on and off at just the right times. Can you discover the trick?

MAKING DC, CHARGE A BATTERY You can change this generator so it makes DC rather than AC. The voltage is still very low, so it's not very useful. If spun very fast, you might be able to recharge a tiny 1.2v rechargeable battery. (Maybe you could add lots more turns of wi re to the coil to increase the voltage?)

Convert 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 wi res, 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 While running the tech shop at the Museum of Science in Boston, I was working on new ideas for exhibits for the Electricity Hall in 1988. I knew that the Exploratorium had an electric generator exhibit where the museum visitor would yank a plastic-embedded coil plate through a row of huge magnets (magnetron horn-magnets from a military radar.) Doing so would light up a small bulb. I just knew that there HAD to be a way which uses more common magnets. So I stacked up a pile of 3" loudspeaker magnets (those black donut things) and waved it past various coils. Finally I wound about five pounds of #26 wire around a ring of nails pounded into a board, hooked up a #49 light bulb, then moved the stack of speaker magnets in and out. This easily lit up the bulb.

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. If anyone else wants to try to make a cheaper or simpler electric generator, they have to do better than I did! MAGNET WARNING WARNING: Keep the magnets away from computers, disks, videotapes, color TV sets, and from wallets and purses containing credit cards. Try this: Keep the generator far from your color TV, turn on the TV, start spinning the nail so the magnet is spinning fast, then bring the generator about 2ft away from the TV screen. DON'T BRING IT CLOSER!!! Keep spinning the magnets, and you'll see a cool wobbling effect in the TV picture, along with some color changes. The field from the magnet is bending the electron beam that paints the picture on the screen. Be careful, if you bring the magnet about 15cm away, the iron sheet inside the TV picture tube will become magnetized and the distorted colors will be permanent.

GOING FURTHER Want an extremely powerful motor or generator? An adult project? Those need stamped-out iron sheets for laminations. But there's another way. Look into Edison's tactic: he took the 1873 Gramme-ring Motor, modified it by adding a separate low-speed commutator, and sold them like hotcakes.

In the Gramme dynamo, the core 'laminations' can be made from a long length of iron wire wrapped as a hoop and doused with epoxy, tar, etc. Form a solid ring. I don't know if fine iron wire is easy to find, but barbed wire and hay baling wire is common. Or buy a toroid transformer and saw all the wire off the core? Then wrap a layer of heavy copper wire around the whole iron ring and mount this on a flywheel. Grind the outer rim flat, so the copper spiral can become its own commutator. Your non-moving stator can be permanent magnets, or non-laminated solid iron blocks, since that part is DC.

Edison's early versions used "paintbrushes" made of fine iron wire as the brushes, later replaced with blocks of slippery graphite.

But then go and do as Tesla did, during his design work for Edison corp. Convert Edison's stator designs into a compact cylinder-shape that hugs the flywheel, and includes enclosed coils rather than those extremely long horseshoe-magnets like Edison's "long legged mary anne" design.

Motor Triva: electric motors were mere lab curiosities until Zenobe Gramme developed a generator which was intended to replace battery banks, since it gave extremely smooth DC output voltage. During an inventors show, an assistant accidentally connected an unused Gramme Dynamo up to another one that was spinning under steam power. The second one started up and ran as a motor; as a *hundreds horsepower* motor. That moment was the start of the electrical age in industry. But it's not much mentioned in American Textbooks, perhaps because it would make Thomas Edison look less of a genius.

DEBUGGING DON'T USE DIFFERENT PARTS. If the light bulb won't light, usually it's becaused different parts were used. Follow instructions. If you changed the magnets, it won't work. So don't use different magnets. If you used a different bulb, it won't work. Use the parts in the list, don't make changes. If you're not using very thin #30 varnish-coated wire, then it won't work. So don't use different wire. Don't use different parts. Before testing anything else, ask yourself if you used the parts in the parts list? If you used different parts, the generator will fail. Notice: it's very important that you use the parts listed, and don't use substitutes.

SPIN IT FAST, IN THE DARK. Sometimes your generator is working fine, but you're not spinning it fast enough. Or perhaps the dim glow of the light bulb is being missed in a brightly lit room. So, go into semi-darkness. Then spin the thing REALLY FAST. Try cranking it with an old-fashioned drill. (Electric drills don't turn very fast.) Or try gluing a tiny wheel to the nail, then rub the wheel on the spinning tire of an upside-down bicycle (don't go too fast or the bulb will burn out.)

ADD LOTS MORE WI RE. If your coil has more than 250 turns, then the bulb glows much brighter. The #30 thin spool of Radio Shack wire is 200 feet long, which gives about 250 turns. If you could wind more turns on your coil, then your bulb would light up at lower magnet speed. Buy two kits of wi re from Radio Shack, then use both spools of #30. Scrape every bit of the red plastic coating off all the wire ends. Then twist the end of the new spool to the end of the old one. This creates a single longer wi re. Be sure to wind the extra wire in the same direction as before.

Better source of wi re: buy a large "Solenoid" from a mail order company, then use Vice-grip pliers to pry open the metal bracket. The hole in the solenoid goes through a square steel plate, and if you pry the rest of the steel frame outwards, you can remove the square plate and take out the wire spool. Peel off the tape, and wind 600 turns on your generator. DON'T USE OTHER MAGNETS, use the large 2-inch rectangular magnets sold by Radio Shack, #64-1899, see their site. Or try Educational Innovations teachersource.com, or try magnetsrc.com. They cost about $2 each, and have no holes through the center. Don't use the smaller 1 inch Radio Shack magnets. Most other magnets are way too weak and will not work unless you spin the magnets incredibly fast, at thousands of RPM (revolutions per minute.)

USING SMALLER MAGNETS

If you can't wait for mail-order of the correct magnets, instead you can use twenty of the Radio Shack 1" magnets 64-1879 Glue them together to form two large magnets.

Here's how I did it. First I formed two magnet stacks: I glued ten magnets in two separate stacks of five magnets each. I used 5-minute epoxy. Before the glue hardens, adjust the magnets so the sides of each small stack are flat, and wipe off the excess epoxy. (To make the sides flat, I laid each stack down on aluminum foil, pressed them down to align the magnets, then peeled off the foil when the glue was hard.) Next, glue two of these 5-magnet stacks together side by side so the stacks are repelling each other. See the diagram below. Glue the narrow side together, so the block will be 2" wide. Then hold them together until the glue hardens. That way the N pole of one stack is near the N pole of the other, and S is near S.