Light Bulb into Plasma Ball

First of all, what the heck is plasma? (I only know the blood version)

And secondly, is this safe? Can my daughter do it for a science fair project? I wish they had given more details on how they did it instead of just showing it.

http://www.educatedearth.net/video.php?id=3528

 

Log in or Sign up to hide all adverts.

Well, just guessing, but I'm pretty sure this experiment requires a high-voltage power supply, and I'm pretty sure that's what the transformer block on the right side of the bulb is. No idea what kind of current is going through this, but I'm going to guess there's a very large change of electrocution with this experiment, unless there's a safe means of doing this that I don't know about (there very well may be).

The plasma is just the molecules in the air breaking down to allow the conduction of electricity from one point to another through the air, and if you want to make good solid sparks, I accidentally discovered a great way to make very bright sparks but not arcs when I was trying to make a buzzer for a science fair as a kid. Here's the recipe...

Firstly, the buzzer mechanism I'm using works like this... Power from a battery goes through an electromagnet, then the other lead of the electromagnet is wired up to the electromagnet's own iron core. A little bell is suspended and allowed to touch this iron core, and a wire from that bell goes back to the battery. The electromagnet is such that when current flows through the system, it pushes the bell away. However, since the circuit is not complete unless the bell is touching the magnet's core, the bell falls back to the electromagnet, to be pushed away again when it hits the magnet, falls back, goes away, etc. etc., repeatedly many times per second to make a nice little ring or a buzz.

I made the electromagnet with a 6-inch long 3/4 inch-diameter solid iron rod (might be able to get someone at a hardware store to slice you a piece this size, but I used a scrap piece from a project my dad did so I'm not too sure on that) and wrapped that rod about 200 times with solid, copper, insullated household wire. Wrap in the same direction and wrap very tightly and very cleanly so that the wires are nice and snug against each other, and you can double-up the wrapping if you need to. With only two small bits of wire now poking off the electromagnet, I wrapped the windings with lots and lots of duct tape, and not the wussy stuff, but the thick, knarly stuff with fibers in it. Lots of wide electrical tape would probably work too. And there you have it, a fairly efficient electromagnet perfect for a number of science fair projects (even salvage it for future stuff if you really wanted, after all, it's a good electromagnet, right?).

Now, the batteries I used were those boxy ones that have little twists of wire for terminals. Get enough of those so that their voltage adds up to 12 volts (later on, these will go in series which means that the batteries are daisy-chained together with positive to the next negative until the positive of one battery and the negative of the other are free for use). 12 volts is fairly safe to work with, but extremely small tingling shocks are not unheard of. To do the wiring, use more of the same stuff you used for wrapping the electromagnet, and get some screw-down wire connectors from the electrical section of your local hardware store. These are good connectors for this project, give a good connection without solder, and you can take them off and on and reuse them if you need.

You'll need a good thing to mount everything together so that a.) all the parts stay at the science fair project, no kids take off with stuff, and b.) when you have things properly adjusted, you don't need to adjust things again. I made the project on a good piece of leftover particle board with a plywood piece mounted vertically on the back to serve as the poster-board. Since I was pretty young at the time, my dad fashioned most of this, but the particle board base was given a fairly large plexiglass enclosing so that kids couldn't screw stuff up (touch,touch,touch...). The enclosing would bolt onto the base, so that you can work on the board without the encosure, but when it came time to it, a kid would have to beat the thing with a crowbar to get it open without a wrench. The batteries were just duct taped really well onto the board, the electromagnet was given some wooden brackets to clamp it to the board and keep it steady. Now, for the bell, it needs to hang from something, so by now you should've already aquired a small bell (we used a jingle-bell-like bell) and you should make sure the electromagnet when powered repells the bell with respectable strength at one end. The bell needs to be part of the circuit, so at one end of the magnet, I pieced together a little arch-like thing made of alluminum coathanger wire near one end of the electromagnet. Aluminum is awesome for this because the magnet will not act on aluminum, whereas the copper thing I tried earlier would actually shake loose due to the magnet pulling or pushing on it. Teather the bell from the aluminum arch-thing with a conductive thread, another piece of household wire is fine if you allow the end at the aluminum to swing freely. Wire this arch to one terminal of the battery, wire the electromagnet core to one of its own terminals, wire the other electromagnet terminal to the other battery terminal, and you should have it! Incorporate a switch though, in fact, you should probably make the switch such that other kids can't just turn the thing on and leave it on at science fairs, you'll burn your batteries out that way.

Maybe not yet... you need to move the arch-thing a bit to get the bell going at a good level, but with enough voltage (12-volts works), a big, blue spark will appear as the bell comes in and out of contact with the iron core. This is not only very cool, but if you get it right, the buzz can be deafening! One word of caution, the sparking itself can make things HOT. BE CAREFUL when touching the bell immediately after a long time running, it might actually burn your fingertips a bit.

But yeah, you can make the project themed to talk about how some inventor made the first electric bell, etc. etc., but that massive blue spark will be the eye-candy. Make sure you get that going good! If you're lucky, you might actually see arc-welding-like spots on the bell and iron core like I did.

 

Log in or Sign up to hide all adverts.

Usually for this sort of thing people use a very high voltage, very high frequence AC power supply. The voltages are huge, but the AC frequency is fast enough that it doesn't effect the body.

 

Log in or Sign up to hide all adverts.

so yes or no, could a 9 yr old do this? Or is it too dangerous?

 

You'd better read the science fair rules before doing this, and yes, it's definitely too dangerous for a 9 year old to duplicate that experiment. There are some places around that have a lot of experience with providing kits and materials to young scientists.

Most of your score will be for the research that you do into this project. If your nine year old girl can search the web and read in books how to make a plasma globe safely from a lightbulb, then go for it. You're going to have to prove it to someone, you know. It might work for the science fair's advisors if she builds it and you do the dangerous work in testing it and making sure it's right.

 

me do the dangerous work?? oh hell no!
My science fair project involved a slinky and a scrunched straw wrapper.

 

Yes this appears to be quite dangerous. He is using a high volatge tranformer on 60Hz power. These transformers are often used to power "neon" signs. they have many turns on the secondary and when a small current is drawn, the relatively small (compared to a normal transformer) amount of iron becomes "saturated" and then that iron is just like an air core transformer. I.e. the peak current is quite limited, but can be leathal.

This is entirely different from the "Tessla coil" which produces the same sort of effect (glow discharges in low pressure gases), but it operates at much higher frequencies, (at least FM band or higher) where the "skin effect" (nothing to due with animal or humman skin) keeps the currents from entering deeply into the body (or copper rod).

It is very irresponsible or ignorance to suggest this as a science project. Much TOO DANGEROUS, and has only "show" (no "tell").

The tell would be to speak about the Pashen curve. I.e. at atmospheric pressure, there is no glow discharge as the energy gained by the very rare free electons by "falling" thru the applied votage´s electric field is too little to free another electron. That is before electron can gain enough energy to ionize an atom, it makes a non-ionizing collsion, and loses the small amout of energy it has gained. As the pressure is reduced, it "falls" farther between collision and if the pressure is low enough, gains sufficient energy on average to produce another electron (ionize some atom) before it becomes attached to some atom. I.e. there is a very rapid multiplication of the number of free electons flowing in the field and when they hit atoms they also excite the atoms to states from which they can decay back to the ground state by giving the excitation energy to a photon they make when decaying back to the ground state.

If the pressure becomes too low the free electrons gains lots of energy but do not hit many atoms to ionize them. (Even those that do hit may not be ionized, but that gets a little more complicated to explain - has to due with fact that the "cross section" is energy dependent and is higher, in general, when the energy avaliable is approximately the energy required or "resonate.") Thus the "Pashen Curve" has a pressure at which the voltage require to product the glow discharge is least, "the pashen minium" pressure and it differs for each gas.

 

In this case, Orleander doesn't know enough about what is involved and he needs to in order to help a nine year old girl do this. She could possibly do this if she were adequately supervised by someone who was knowledgeable.

An alternative is to buy one at Radio Shack and do the research to explain how it works. I was thinking that even a plasma globe might be available somewhere in the form of a fairly safe kit.

Most likely the video shows a safe version. We can't tell because we don't know what the transformer is hooked up to.

 

Billy, one very minor correction. Telsa coils (and commercially available plasma balls) typically operate at 50-100kHz. The skin effect sets in at frequencies much lower than most people realize, something like 20-30kHz. Ultrasonic frequency more or less.
Otherwise, I couldn't agree more. Using a neon sign transformer is extremely dangerous. Besides, building a suitable high frequency power supply (powered by a few AA bateries perhaps) isn't all that difficult. Now that might be a science project. I would bet that there are plans on the net if someone wanted to do some searching. I seem to recall seeing complete plasma ball kits in some electronics hobby catalogues.

 

We don't actually know what the neon sign transformer was powered by. It might have used a battery-powered inverter supply. I've built stuff like that before.

 

yeah, kits are for cheaters. Dang, it sure did look cool.

Thanks All!!!

 

Thanks. I was both not sure of the frequency required to keep the current out of your nerves etc and also wanted to keep it as simple as possible. I knew "radio frequency" would not be adequate, so said "FM" to be simple and knew that was high enough. (I had a first class commercial radio license* and worked several summers for radio WCHS in Charleston W Va as summer vacation relief while still in high school. I got a bad RF burn once (down to the bone) - not a drop of blood as it self carterized. WCHS was (is?) 50KW directional radiator with three antennas to produce non-intefering notches in the transmitted field. We had to go to the "dog houses" at the base of each antenna and measure antenna current (and relative phase) and tell partner at the transmitter feeding them the results. One finger got too close to strap carrying about 25KWs. It took a few weeks to heal.
------------------------------
*I may have been the youngest to hold one. My doctor father had the chief engineer as a patient. I was already a "ham" and he told me he would pay me full adults pays at least for 12 weeks if I got legally qualified as he would other wise need to hire a fifth man full time.

 

When you're talking 10's of kw, you can get burned badly skin effect or no. Ouch! For low power, you're pretty safe physiologically above 30kHz or so. As the frequency rises, the conduction skin thins. In electronics, this starts to be a major problem ~100mHz, (FM and lower TV band). Particularly in tuned LC tanks, and you see a lot of gold and silver plating to combat it.

IIRC, most of Tesla's work was targeted at around 100kHz, but that had a lot to do with "earth resonance" as he called it. He beleived there was a narrow band in that neighborhood that would allow better coupling between his coil, the ground and the sky(the ionisphere more or less). Better performance for power transmition or so he thought. A genius at experimental tinkering, not so good at theory. He never really beleived in EM waves, thought of radio as direct conduction along the sky with the ground as a return path.

 

Interesting. I did not know Tessla was ignorant of Maxwell etc. find it hard to believe, but am not an expert on Tessla.

The frequency range in which the Earth and ionosphere does act as a wave guide is well known. You can hear (with reciever,of course) lighting strikes that occurr ANYWHERE in the world. They are called "whistlers" and with timed mutiple detections, locate them, tell things about the then existing global factors that control the speed of propagation etc. I forget the frequency of the "whistler band" and as usual, am too lazy to search for it.

 

Not so much ignorant of Maxwell and Hertz, he just thought they were wrong, or at least tranverse waves weren't the primary phenomenon operating in his experiments. Probably on some level he realized that if you were stuck with an inverse square falloff, then his power transmission ideas were doomed to fail.
Fascinating character Tesla. Invented a surprising number of things vital now in everyday life. (induction motors and ac current off the top of my head) And yet he never quite seemed to be able to fully grasp the theoretical side of things, which led him to wildly extrapolate ideas based on limited experiments.

 

The video makes it look very dangerous, but the end result is the same type of thing you can buy in a novelty store for under $100.