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EMP generator using a spark gap

  1. Nov 7, 2004 #1


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    Hi, i live in the UK and currently studying physics at A-level. I have chosen to investigate EMP and its effect on electrical systems for a project. How would i build a generator? Am i right in saying all i would need is a fairly large capacitor and a spark gap? What sized voltage are we talking here to get a measurable EMP? Could i measure the EMP using an ocsilloscope? I would appreciate it if you could offer some insight. I have a limited knowledge of physics (bare in mind that im only 17!) so please don't be too complicated in your answers :smile:
  2. jcsd
  3. Nov 7, 2004 #2

    Yes to all your questions. Any electrical arc generates an EMP. An automobile’s ignition system generates EMP and in weak reception areas can be heard on the radio. To damage electronic components at any distance more than a few millimeters will take considerable power. You’re looking at 10’s of thousands of volts and high currents, more than I suggest you attempt.

  4. Nov 8, 2004 #3


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    i see, thanks. So would a van derr Graff generator produce EMP that could be heard on a radio?
  5. Nov 8, 2004 #4
    "EMP" is a very general term since it can be defined as any "pulse" that is produced anywhere across the electromagnetic spectrum.

    So, anything that is producing staccato pulses at any frequency could be loosely considered "EMP", although not necessarily "destructive".

    A quick search in google for "emp generator" produced this link at the top of the page:


    Looks like lots of HV stuff, so try not to fry yourself. When you begin messing around with capacitors that are charged up in the kV regions, you don't necessarily need to make full contact with the electrodes to get accidentally hit with a discharge.

    At these higher voltages there's always the possibility that you might get close enough to allow the charge to ionize the air-gap between YOU and the electrode. This means the charge can "reach out" and bite you when you might not otherwise expect it. :eek:
  6. Nov 9, 2004 #5


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    Im looking at buying a capacitor on the internet for this project. I need a 6000v capacitor and ive seen a huge variety in prices. The ones with higher farad values seem to be more expensive. Why is this, e.g. a 40kv 1pF capacitor is 6$ whereas a 10kv 0.1F capacitor is 70$!
  7. Nov 9, 2004 #6


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    0.1F is a *tremendous* amount of charge....
  8. Nov 9, 2004 #7


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    maybe it was lower, but im just wondering what the advantages are of having a higher capacitance but the same p.d. on 2 different capacitors?
  9. Nov 14, 2004 #8
    Well here is a unusal favourites link I found in my browser. Expensive but you might find it interesting if you are going for a home made job. I think the easiest way to generate a large emp involves explosives. Whatever they are all probably illegal in built up areas (or any area if the pulse is strong enough) and for very good reasons.


    Jesus: 1Mfd Capacitors :/
    Last edited: Nov 14, 2004
  10. Nov 15, 2004 #9
    A good place for information would be here:


    Many members on the 4HV forums have already designed, built and tested these types of things and can give you actual information.

    Just don’t meantion my name there...
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