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Re: [TCML] Science Fair Project
Hi Jim, Thanks so much for your time. I can tell you are a science fair expert!
And sorry for not getting back to you sooner. My mom works weekends and I needed
some help to understand everything you wrote. I had no idea everyone would
respond so quickly! You’ve given me a ton of information so I am not going to
respond point by point. Instead I’d just like to say that after multiple
readings of what you wrote, I’m thinking the spark gap is the area I’d like to
So I’m beginning to research various types in order to make some predictions of
performance. I also have not built the coil yet so I don’t have a measurement
for the standard spark gap. You have pointed out that I need to quantify my
prediction -- how much longer or how much more efficient. You mention measuring
coil output. Since spark length is hard to measure, would the distance the a
light bulb can be away from the coil and still receive power (light up)be a good
way to measure output?
I’m also hearing that “best” is not a result. “25% more powerful” is and that
the reason why is important. That is where I don’t know enough yet about spark
gaps to make a prediction.
I have read the information on safety and I’m looking at a battery powered coil.
Thanks again for all you help… Jonah
----- Original Message ----
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
Sent: Fri, November 16, 2012 5:47:57 PM
Subject: Re: [TCML] Science Fair Project
On 11/16/12 9:17 AM, plasticanvil wrote:
> I would like to experiment with a Tesla coil for a Science Fair in
> mid-January. I can’t just do a show and tell. I need a hypothesis and a
> variable, data collection and something I can prove. I'd like to measure the
> performance of the Tesla coil and change some variable to increase it. This is
> kind of the idea I’m thinking of… varying the coil rotations or length, type
> capacitor, or the gap length to produce different results.
A good quantitative experiment might be to experimentally validate John Freau's
empirical "spark length in inches = 1.7*sqrt(input pwr in watts)" formula..
Build a coil with a breakout point and go to a ground point (something like a
ring stand).. Use a variac to adjust the power. Carefully measure the AC power
going into the coil. At each power setting, adjust the coil for peak
The challenge is that for a given coil size, you don't get a lot of power range
where it works. When you get too low, it stops breaking out.
Maybe another way is to vary the loss in the primary by using a variable
resistor (salt water is easy, and will take the HV, and you can measure it with
a standard meter with the power off)
You run at constant voltage into the system, so the only thing varying is the
series resistance. You can measure current and voltage .. but to do it right,
you'd really need to use an oscilloscope (but maybe you have one available or
can borrow one).
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