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 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 wires. All wires are full of electric fluid. Modern scientists call this the "electron sea" or "electron gas." It is not invisible, it actually gives metals their silvery shine. The electron gas is like a silvery fluid. Sort of.
When a circle of wire surrounds a magnetic field, and the magnetic field
then changes, a circular "pressure" called Voltage appears. This circular
voltage trys to force the movable charges in the wire to rotate around the
circle. In other words, moving magnets 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. But if the circuit is "complete" or "closed", then the
magnet's pumping action can force the electrons of the coil to begin
flowing. This is a basic law of physics, and it is used by all
coil/magnet electric generators.
When the circuit is closed and the magnet is moving, charges in the metal are forced to flow. The charges of the light bulb's filament are 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.
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?
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 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
When your hand spins the magnets, you can feel the extra work it takes to light the bulb. Try spinning the magnets with the bulb disconnected. The magnets become much harder to spin. 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 adjacent magnet poles, so the field doesn't extend out through the coil. On the other hand, when you make a single stack of magnets instead, the field extends outwards for many inches, and if you spin the single magnet stack, the field cuts through the wires and pumps their electrons into motion.
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 wires, 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
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 wire to the coil to increase the voltage?)
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. There is an easier 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 it
takes about 3/4 volts to force charges through a diode, and this voltage
subtracts from your generator output. Try doubling the amount of wire in
the generator. Also try using a special diode with
lower voltage, such as 1N5819 from digikey.com.
MAGNET WARNING
WARNING: Keep the magnets away from computers, disks, videotapes, color TV sets, and 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.
DEBUGGING
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. Or try sticking a little wheel on the nail, then rub it on the spinning tire of an upside-down bicycle (don't go too fast or the bulb will burn out.)
DON'T USE DIFFERENT PARTS. This generator cannot power a normal
flashlight bulb, it needs the special 25-milliamp, 1.5-volt bulb sold by
Radio Shack. Don't use a normal flashlight bulb, since that kind of bulb
requires way more energy before it starts to glow. If you simply cannot
find the Radio Shack 25mA bulb, you can use a 1.5V 40mA bulb, but add
twice as much magnet wire to your coil (buy two of those kits of magnet
wire.)
DON'T USE OTHER MAGNETS, use the large Radio Shack rectangular
magnets. They cost about $1 each, and have no holes through the center.
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.)
If the generator refuses to work, inspect the spot where the wires twist
together. The generator coil has a very thin red plastic coating, and you
must clean ALL of this coating off the wire ends before twisting them to
the light bulb wires. Also, the tips of the light bulb wires must be
stripped clean of plastic. The metal wires must touch together.
If there is plastic between the metal of the generator wire and the light
bulb wire, the circuit will be "open" and no charge will flow.
Make sure the magnets are positioned correctly. Do this: stack up all
four magnets so their widest faces are clinging together. Then jam the
nail through the crack in the middle of the stack. Then take this
apart, and re-assemble it inside the generator in the same way.
Be sure to follow the instructions and diagrams. You MUST wind the coil
so the coil goes across the side of the box which has the nail hole. If
you wind it so no coil is crossing the nail-hole side of the box, then the
magnetic fields won't cut across the wires, and no electric voltage will
be created.
Also, don't wind the coil over the open end of the box, otherwise you
won't be able to get your fingers inside to make changes to the
magnet.
If you cannot spin the magnets fast enough with your fingers, try a
"twist drill" or hand-crank drill. Clamp the nail in the end of
the drill and spin the magnets as fast as you can. An electric
drill may work too, but most electric drills don't move as fast as
the hand-cranked type.
DON'T SUBSTITUTE THE MAGNETS OR THE LIGHT BULB WITH A DIFFERENT TYPE. It
needs strong magnets and a low-voltage, low-current incandescent bulb.
If your generator doesn't work, check the parts again and make sure you
have the right type of magnets and the right type of light bulb. Don't
use fewer magnets. Weaker magnets may work in theory, but you won't be
able to spin them fast enough by hand, and a high speed motor will be
required in order to spin them. Don't use an LED. A red LED could work
in theory, but you need at least 1-1/2 volts to barely light one up (the
green or blue kind need even higher volts.) The light bulb is better
because it lights up at less than 1/2 volt. (If you really must light up
an LED, use the red kind, and also add about three more spools of #30 wire
to your generator coil.)
Perhaps your luck is bad and you got a dead light bulb. To test it, get
any new, fresh 1.5V battery (the size doesn't matter.) Take the bulb off
the generator, then touch one wire form the bulb to the top of the battery
and one wire to the bottom. The light bulb should light up brightly. If
it stays dark, the bulb is bad.
The generator can be improved by using more turns of wire. You used only
the spool of #30 wire. With more wire, the magnets don't have to spin as
fast to light the bulb. Connect the thinnest of the remaining spools of
wire to one end of the wire that's already wrapped, making sure to scrape
the wire ends totally clean before twisting them together. Make sure to
wind the extra wire in the same direction as the rest of the coil.
Or, if you want to light your light bulb REALLY bright, buy a second kit
of wire, hook the second #30 spool to the coil you have already made, then
wind all the wire onto the coil. Be sure to clean all the red plastic off
the ends of the extra wire that you've added.
NEXT: DEBUGGING
(PREV: CONSTRUCTION)
