A DEMONSTRATION OF 'CHARGE CLUSTER' PHENOMENA
Date: Wed, 6 Dec 2000 11:15:57 -0700
From: Hal Fox
To: 
Subject: Something for School
Dear William Beaty,
Ken Shoulders, in one of his papers, describes the following. It is a
very instructive experiment and may lead some students to become one of
the early charge-cluster engineers.
Use standard aluminum foil. Coat it with a mixture of finest
silicon carbide powder (used as a grinding powder for polishing)
mixed with enough epoxy to make it stick.
There is nothing exotic about mixing the epoxy and silicon
carbide granules. We used black friction tape applied to the
aluminum foil and then squeegee the paste onto the layer between
the two tapes. You can try different thicknesses. We determined
that about 0.006 inches was about optimum.
Connect a high voltage d.c. connection to the foil and the other
to a needle. You will need to have a high-voltage source, such
as from a TV power supply (from any old TV). Try the aluminum
for both positive and negative connections. Slowly bring the
needle closer to the aluminum (black coating toward the needle).
According to textbooks, it requires about 10,000 volts per
centimeter to establish a spark or an arc. Have students
determine at what distance and at what voltage arcs or sparks
appear in this experiment.
You will note that you can create a visible (especially in the
dark) flow of ions (probably caused by electrons bombarding air
molecules) between the needle and the aluminum before the spark
zaps. In addition, you will find the following:
1. Sparks are produced at much lower voltages than the textbooks
predict.
2. The spark will entirely vaporize the silicon carbide (which
has a very high vaporization temperature). Have students look up
the melting and vaporization temperatures.
3. There will be a hole in the aluminum.
4. You may observe (when aluminum is anode) that the spark goes
past the aluminum and turns around and goes back to the aluminum
electrode.
Why does this arrangement produce sparks/arcs at lower voltages.
I suggest that it is because most of the voltage drop is across
the non-conducting silicon carbide layer. This is a method of
creating a charge cluster.
ABOUT MEASURING
Ken works much with single shots. He charges a small capacitor
to a given high voltage (maybe several hundred volts). It is
easy to measure the voltage on the capacitor before a "shot" and
after the shot and compute the energy used. Similarly, the
output is captured in a capacitor. It is easy to compute the
power output supplied to the capacitor. Shoulders has shown that
it is relatively easy to get ten times as much electrical energy
out as input electrical energy. The trick is to provide an input
pulse that is very short to make the charge cluster and to make
the output pulse as wide as possible. This is not simple because
one needs to produce clusters using nanosecond, high-voltage
pulses.
Have Fun!
REFERENCE
http://amasci.com/weird/evexp.html
Created and maintained by
Bill Beaty. Mail me at:
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