1. Visible Current:
Connect a single Visual Electricity unit in series with a handcrank DC
generator and a small lightbulb.
Crank the generator to light up the bulb, and the charge-flow or "current"
in the LEDs will flow. Crank slow and fast, or reverse cranking
direction, and note the behavior of the charge-flow.
- Note that the the particles of "electricity" inside this "wire"
are always there even when the generator is not being cranked. This
illustrates the fact that the source of "electricity" in a circuit
is not the generator. The charges exist whether the generator is
cranked or not. The charges are actually provided by the metal of
the wires. They remain in the wires even when the generator is
removed, and even if the wires were to be melted down and formed into
some other metal article. Doesn't this suggest that all metals must
contain movable charges? Thats right, they do. The "electricity"
which flows inside any wire is supplied by the wire.
- Note that as you crank the generator, the charges instantly start
moving and the lightbulb lights immediately. This occurs even though
the charges themselves move slowly. This illustrates that
"electricity" does not move at the speed of light. In fact,
electric charges are simply used to transfer electromagnetic wave-energy
similar to the way that a solid rubber drive belt is used to transfer
mechanical energy. When any part of a drive belt is forced to move,
the entire belt also must move, and energy spreads to all parts of
the belt. Because the charges within a >CIRCUIT< form a loop, they
behave like a belt too, and when any part of them is forced to flow,
the entire loop of charges moves as a unit. This sends electromagnetic
wave-energy to all parts of the circuit almost instantly. The flowing
particles of "electricity" are the medium over which waves of electrical
energy flow, but they are not the energy itself.
- Crank the generator continuously so the bulb is lit. Now stop, and
then crank the generator rapidly back and forth. The bulb still lights,
although with a flicker. Wiggle the crank faster, and the flicker
grows less. You are illustrating the difference between AC and DC.
With DC, the charges move continuously around the loop. With AC,
the whole loop of charges moves back and forth.
- No matter which way you crank the generator when creating AC in the
previous demo, energy still flows in one direction: from generator
to bulb. But while this was happening, the glowing electrons sat in
one place and wiggled. This illustrates the difference between
energy and charge. It also points out the little-known fact that
electrical energy flows along BOTH wires as it moves from generator
to bulb.
2. AC to DC:
Use 4(four) Visual Electricity devices in combination with four 1N4001
diodes, a handcrank generator, and a light bulb. Assemble the four diodes
into a "Full Wave Bridge Rectifier" circuit with the generator connected
to the AC side and the light bulb connected to the DC. (Put two VE
devices in series with the generator leads, and two more VEs in series
with the light bulb leads.)
Crank the "AC" generator forwards, back, or rapidly back and forth. You
will receive an immediate, gut-level lesson about the way that AC is
converted to DC.
3. MOTOR AND GENERATOR:
Use two Visual Electricity devices, and two handcrank generators. Connect
the two generators together using the VEs in parallel. Turn one generator
rapidly, and the other one will be driven as a motor. What will the
"electricity" do? Have somebody grab the "motor" and stop it while you
are cranking the "generator," and observe the change in charge flow.
4. RECHARGABLE BATTERY:
Use two Visual Electricity devices, a handcrank generator, and a 1-farad
supercapacitor.
Connect the two VE devices in series with the leads between the generator
and the supercapacitor.
5. SWITCH:
Use two Visual Electricity devices, a handcrank generator, a light bulb,
and a switch.
Crank the generator and have someone open and close the switch.
6. MORSE CODE:
Use two Visual Electricity devices, a handcrank generator, a light bulb,
and a Morse Code key connected in series.
7. AC MOTOR:
Use two Visual Electricity devices, a handcrank generator, and a
shaded-pole AC motor.
Crank the generator back and forth very rapidly, and, if the motor's
bearings have a sufficiently low friction, the iron and copper rotor will
slowly turn in just one direction.
8. BAR-MAGNET BASED GENERATOR:
Use one Visual Electricity device, a large ceramic disk magnet, and a
1-lb spool of copper wire of 24-gauge or smaller. Connect the ends
of the wire spool to the VE device.
Place the ceramic magnet upon one end of the spool, then suddenly yank it
away.
9. HEATING OF THIN WIRE FILAMENT:
Use four Visual Electricity devices and a handcrank generator. Connect
three VEs in parallel. Connect the fourth one in series, then connect the
handcrank generator across the ends of this assembly. The three VEs act
together as the "wide" wire, and charges there can flow three-abreast.
What happens as the charges flow from the 3-abreast section and into the
"narrow" wire formed by the single VE device?
CAVEATS
Because the LED pattern advances in discrete steps, it is very easy for
students to receive the mistaken idea that electric current within a wire
is discontinuous in the same way. They might wrongly believe that
electrons "jump" along rather than flowing smoothly. Charges in a
conductor do not jump along, nor do they jump from atom to atom. The
jumping motion of the LEDs is an "artifact" of the system, and it must be
ignored. In future processor-based versions of this product, crossfading
between adjacent LEDs (based on PWM) will be employed in order to
eliminate the problem. The present version is the inexpensive non-CPU
"quick and dirty" approach.
- Bill Beaty, 6/28/95
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