The
Visible Pinball Machine
This exhibit is housed entirely in clear acrylic. It is fully
functional down to it's Coin Mechanism, so you have to put a
token in to make it work. The playfeild is translucent, as in
the bottom board holding all the relays and score motor. This
is lit from beneath the bottom board with a switch-able lamp
so the viewer can run it off in order to see the arcing of the
switches. The display is best experienced with two or more people,
one playing the machine and the others watching the innards
come to life. It is like having X-Ray vision as you are able
to see every part of a working pinball machine. |
Series/Parallel
Circuits
This exhibit consists of a power supply, two volt meters, one
large ampere meter and four smaller ampere meters which are
connected to individual light bulbs. The four light bulbs and
their accompanying ampere meters are on rotating blocks, which
make it possible to connect them to prominent bus bars in either
serial or parallel fashion. Regardless of this type of connection,
18 watts are consumed to power the lamps. The various meters
relay the voltage and amperage measurements very clearly with
any configuration. |
Zero
to Sixty
This exhibit allows for the exploration of low voltage DC and
AC currents, which one can observe the effects of the currents
on lamps, meters, a speaker and an oscilloscope. Three sources
of current are available: a DC battery, a step-down transformer,
and a variable 0 to 60 cycle source. Zero to Sixty makes it
very easy to explain and show the difference between alternating
and direct current. |
Glow
Discharge
This exhibit demonstrates electrical effects in a low pressure
gas. The visitor can vary the voltage and air pressure in a
large cylindrical tube. If gas is leaked into the tube up to
atmospheric (or almost atmospheric) pressure, all glowing ceases.
As the vacuum pump reduces the pressure in the tube, it begins
to glow pinkish-orange. As the pressure further decreases, the
glow breaks up into light and dark spaces (Crooke’s dark
spaces). After this phenomenon, the orange glow disappears completely
leaving behind a blue violet glow which slowly gets dimmer until
the tube is once again dark, except this time at a low pressure.
A magnet hangs from the exhibit which allows the visitor to
demonstrate that moving charges can be deflected by a magnetic
field. Meters are provided, which give an indication of the
current flowing in the tube, as well as the gas pressure. |
Hertz
Resonator
This exhibit is a dumbbell-shaped transmitting antenna connected
to a spark generator. At the center of the dumbbell is a small
gap, which the spark generated by the high-voltage circuitry
jumps across. The oscillator sends out a polarized electromagnetic
wave in the radio spectrum. A simple dipole antenna made of
an aluminum rod is attached to a piece of structural plastic.
The four-foot-long receiving antenna has a neon lamp at its
center which picks up the radio waves emitted by the oscillator.
The neon lamp lights, but only when the antenna is held horizontally
in line with the transmitted signal. When the receiving antenna
is held vertically, the lamp remains dark. This exhibit clearly
shows that a radio frequency signal can be transmitted and received. |
Motor
Effect
This exhibit demonstrates the forces on a current carrying wire
when placed in a magnetic field. A large wire carrying hundreds
of amperes is placed inside a large gap-magnet. The wire flies
up with considerable force which the visitor can feel by pushing
on the wire. |
Transformer
This exhibit demonstrates the workings of a transformer, showing
that the electrical current actually undergoes two transformations.
The first is from electric current to a magnetic field, and
the second is from a magnetic field to an electric current.
The exhibit also shows that only alternating current can be
transformed, and not direct current, since the secondary coil
only responds to a changing magnetic field. The visitor can
change the magnetic field by either changing the current in
the primary coil with a lever that controls the DC power supply,
or by leaving the current on and sliding the secondary coil
into and out of the primary coil’s magnetic field. We
also hang a regular bar magnet on the exhibit which the visitor
can move into and out of the secondary coil. |
Floating
in Copper
This exhibit is an elegant expression of a relatively simple
phenomenon. Taking advantage of the slowing effects of eddy
currents, visitors can make a central magnet literally float
in space between two large pieces of copper. Notice that the
closer the magnet is to the copper, the slower it moves. As
the visitor draws the lower magnet up with the upper magnet,
the motion induces eddy currents that serve to slow the lower
magnets motion. This effectively sets up a feedback system slow
enough for visitors to keep the magnet suspended in mid-air. |
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