Science Buddies: "Ask an Expert"

Hello everyone,

I'm really interested in an experiment listed on this site (Link: http://sciencebuddies.com/mentoring/pro ... ?from=Home). It involves creating a spark using dielectric breakdown, coil apparatus, interrupters, the works. It sounds really interesting but I'd like to take it to the next level. Does anyone know of any safe way to harness this type of power?Perhaps use it to turn on a light or power a generator?
Any ideas would be appreciated. Thanks!

I suggest you look into Tesla coils, another name for a variation on this project. They can be a lot of fun! Flourescent lamps light up in the vicinity of an operating one, sometimes even with out discharge directly to them. If you want to see a demonstration, try searching http://www.youtube.com for Tesla coil.

Thanks! I looked up tesla coils and that sounds like it would be amazing to build one but very diffucult. I'm up for the challenge but my funds and knowledge is limited on the subject (though I am continuing to research!). The most detailed instructions I found were on this link: http://bizarrelabs.com/ind2.htm . Do you know of any smaller or less convoluted model I could make? That one seems much to large for a school science fair!

Does anyone know of any safe way to harness this type of power? Perhaps use it to turn on a light or power a generator?

Both https://www.sciencebuddies.org/mentorin ... ?from=Home and http://bizarrelabs.com/ind2.htm are apparatus similar what Tesla experimented with. They involve interrupting a low voltage direct current to produce a changing electromagnetic field and transforming it into a very high voltage. The whole purpose of Tesla experimenting with this kind of apparatus was to produce a very high voltage for experimental purposes to study things like dielectric break down.

If all you want to do is power a light bulb from a 6 volt battery, a PR4 (4 cell) bulb is about as safe as you can get.

Electrical generators typically convert mechanical rotational energy into electricity (the opposite of electrical motors) so I don't follow the logic of your question.

So what are you really interested in investigating? Science isn't engineering so it doesn't always require a lot of expense.

I can think of two very similar highly engineered applications:

The closest exists in every gasoline powered automobile. Induction coils produce high voltage from an interrupted battery current to cause spark plugs to ignite an air/gasoline mixture in the cyclinders.

A lower voltage similar application is the conversion of DC voltage into AC voltage. These are called inverters and are used in Recreational Vehicles and other camping activities. The problem with experimenting with building inverters is that things you would want to try powering are typically easily damaged if the voltage or frequency or wave shape is not what they are designed for.

Most of the cost of conducting many electrical experiments is the cost of measurement equipment.

Okay,

I think what I would like to do its build the spark generator described on http://sciencebuddies.com/mentoring/pro ... ?from=Home and test the dielectric breakdown voltage of noncombustible gases. However, I've found three problems with that.

1) I can't find the dielectric breakdown voltage for any of the gases I want to test!

2) How can I seal the spark gap in a container?

3) Where in the world can I get these gases for a price within my budget?

Also, the article says...
In order to generate sufficient voltage to create a spark, the secondary coil should have orders of magnitude more turns than the primary coil. A ratio of 750–1000 is a good place to start. In order not to exceed the power rating of the current-limiting resistor, the ratio of turns (secondary:primary) should not exceed 1000:1.

Now does that mean for every 75 (or 7.5) turns I have in the primary coil I should have 100 (or 10) in the secondary? Is there a minimum number of turns?

Thanks for all your help everyone!

1) I can't find the dielectric breakdown voltage for any of the gases I want to test! 3) Where in the world can I get these gases for a price within my budget?

What gases do you want to test? Maybe we can help with where to find some preliminary information and suggest some possible sources of gases who might help out a science fair project participant.

2) How can I seal the spark gap in a container?

A lot depends on the voltage involved and what the pressure difference is. Have you had a high school chemestry lab where you bend and manipulate glass tubing? If you have, then you can probably adapt some methods and put a small diameter solid bare wire through a glass tube and heat sealing one end and then placing the glass tube through a rubber stopper. Hot glue is something else that can be tried. The goal will be to use insulating materials and spacing.

Also, the article says...
In order to generate sufficient voltage to create a spark, the secondary coil should have orders of magnitude more turns than the primary coil. A ratio of 750–1000 is a good place to start. In order not to exceed the power rating of the current-limiting resistor, the ratio of turns (secondary:primary) should not exceed 1000:1.

Now does that mean for every 75 (or 7.5) turns I have in the primary coil I should have 100 (or 10) in the secondary? Is there a minimum number of turns?

A ratio of between 750:1 and 1000:1 is a good place to start. This means for every single turn on the primary, you need 750 to 1000 on the secondary! Have fun winding! You need enough primary turns to make a good enough electro magnet to pull the normally closed relay contact open. To minimize the number of secondary turns you need, you want to keep the number of primary turns small.

BEWARE: There are still be a few minor issues with the parts list and proceedures that have not been corrected yet.

Using the bare (uninsulated) 12 AWG copper wire in the material list for the primary is wrong. When it is wound on a metal bolt, it WILL short circuit the coil making for a poor electro magnet and a poor electro magnetic field for a transformer. Type TWHN solid 12 AWG copper wire or similar should be called for if this is to be used for the primary winding.

The relay contacts are shown incorrectly. The normally closed contacts should be oriented away from the bolt head so that when current flows, the primary and bolt act like an electro magnet and open the contact. The normally closed contacts should be wired as shown, it is just the mechanical orientation that is wrong.

The description of the building of the apparatus should indicate that the Neef vibrator should be constructed and tested and be in good working order BEFORE winding the secondary! This should be done to allow working with the circuit without the high voltage danger!

Hi Alexis,

Please consult: http://www.blazelabs.com/e-exp12.asp It may help in determining the dielectric breakdown voltages of various gases. Note: the PDF file at the bottom of the page, which would have made everything really useful, is missing. So, you may need to use the chart.

What gases do you want to test? Maybe we can help with where to find some preliminary information and suggest some possible sources of gases who might help out a science fair project participant.

I'm thinking about writing to some professors at Marquette University which is where both of my parents went to college. My father had a master's in chemistry(sadly, he is deceased) and my mom a master's in computer engineering. My mom has alot of connection and knows many of the people my father worked with. Marquette's is really close to where I live so transportation won't be an issue if one of them will agree to be my mentor.

Have you had a high school chemestry lab where you bend and manipulate glass tubing?

Unfortunately, no. I'm a freshman and am actually taking Accelerated Biology.

A ratio of between 750:1 and 1000:1 is a good place to start. This means for every single turn on the primary, you need 750 to 1000 on the secondary! Have fun winding!

Oh great...I was hoping it didn't mean what I thought it meant! So this is going to be layers of wire right? So I need insulation between each layer.

Also, thanks for the warning about the errors in procedures.

See if your biology teacher is willing to teach you some glass tubing safety and construction techniques or introduce you to a chemistry teacher who will.

If not, then you can probably find an eye dropper with the correct outside diameter to fit in the hole of a rubber stopper. Hopefully your mother remembers enough chem lab safety guidelines and can supervise. You definitely need adult supervision! Be sure and wear protective clothing and safety glasses, take the rubber bulb off the eye dropper, lubricate the outside of the glass with glycerin and holding the side of the eyedropper in several layers of a towel with your fingers, insert it with a twist or rotation into and through the rubber stopper (again held by the side with fingers). CAUTION: DO NOT push on the end of the eye dripper and keep your palm and wrist and other body parts well clear of both ends and the direction of travel should something let loose or break. The towel is meant to protect your fingers should the glass break! Insert a bare wire through the eye dropper and seal the inside of the eye dropper with hot glue.

Dry glass has a very high dielectric constant which makes it ideal for insulating a high voltage electrode through other materials. Ceramics with glass glazing are used commercially on spark plugs and feed through capacitors for similar reasons.