Out of curiosity, I have a question about high voltage electricity sources. Hypothetically, the requirements are that the source must be no larger than a water bottle (although smaller is better), and that the source is capable of producing an arc at least 1 meter in length (longer is better). The source doesn't have to be able to output continuously and can be pulsed, although the time between pulses should be no longer than 1/2 of a second. I am aware that tesla coils can produce large sparks in small packages, but I do not know if they would be the best option for the hypothetical situation or if they are even capable of meeting these criteria. Perhaps some sort of capacitor array?


2 Answers 2


You will need 3 × 10^6 V (three megavolts) to achieve a spark in dry air. That's rather a lot.

However, people have built hand-held Tesla coils that achieve roughly what you're asking for: http://www.rmcybernetics.com/projects/DIY_Devices/plasma-gun-2.htm (and they'll even sell you the parts!) As "Guess Who" points out, it's quite a challenge to avoid insulation breakdown inside your device.

This exploits the tendency of charged sharp points to spray ions into the air, reducing the breakdown voltage considerably.

  • \$\begingroup\$ That gun is awesome +1 \$\endgroup\$
    – Andy aka
    Jun 20, 2013 at 21:24
  • \$\begingroup\$ Thanks for the input! This is why I love this website - there's always knowledgeable people willing to help and suggest really cool solutions. \$\endgroup\$ Jun 20, 2013 at 21:25

The (hypothetical) requirements for your device are insanely unrealistic. Air breakdown voltage (voltage required to create a spark of a certain length through air) varies based on a ton of things, but in general, the "standard" value (all variables aside) is about 3x10^6 V/m. That's a huge voltage. I remember hearing from a professor once (and this could be outdated or completely wrong information) that on even the best of days, it takes about 100,000 volts to create an inch of spark. To create a spark that's a meter long, with circuitry that's the size of a water bottle is, dare I say it, impossible.

  • \$\begingroup\$ Well I did say hypothetical! I certainly wouldn't say impossible though. According to your "standard" value of 3,000,000 volts, I'd say I've heard of stun guns "claim" to have voltages exceeding that voltage, although it would only last for a short time, like a lightning. I said that the source could be pulsed. My question- would it be hypothetically possible to have an array of capacitors, or super capacitors, that can discharge a voltage around 3,000,000 volts that is the size of a water bottle? Also, if so, how fast (at what rate) could said hypothetical capacitor(s) charge and discharge? \$\endgroup\$ Jun 20, 2013 at 21:22
  • \$\begingroup\$ Dielectic breakdown will be your main problem with trying to build a 3MV capacitor; it'll just leap straight across the plates, or through several centimeters of polyethylene insulation. \$\endgroup\$
    – pjc50
    Jun 20, 2013 at 21:35
  • \$\begingroup\$ Well, a mere 500kV can get you a spark way bigger than 1m: youtube.com/watch?v=PXiOQCRiSp0 \$\endgroup\$
    – Phil Frost
    Jun 20, 2013 at 21:47

Not the answer you're looking for? Browse other questions tagged or ask your own question.