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Static charge - capacitor

  1. Mar 26, 2009 #1
    Dear All
    Suppose there is a powered on circuit which consists of a capacitor.Can a static charge come and reside on the capacitor which is working in the circuit ?

  2. jcsd
  3. Mar 26, 2009 #2
    Capacitors can self charge.
    You can short a capacitor, remove the short and some time later (hours, days, weeks or maybe months) the capacitor will self charge to some voltage.

    High voltage, high power capacitors should have a wire shorting the capacitor when not in use.
  4. Mar 27, 2009 #3
    How could I build a device to release the static charge of a capacitor by flipping a switch? I Would like to use a 9V battery and a 100uf 330V camera flash capacitor. Set a SPDT to a charge mode, wait, flip switch to discharge and see spark jump across a gap. What should I make the gap out of? Thanks
  5. Mar 28, 2009 #4
    Some capacitors self charge and some don't

    My experience has been with film type capacitors.

    If you wish to check capacitors for self charge, get some old used capacitors.
    Let the capacitors sit open circuit for several days.
    Place a high impedance voltmeter across the capacitors. The voltmeter should read a voltage and the voltage should decrease as the capacitor discharges.

    If testing large high voltage capacitors, be careful, they can charge up to dangerous voltages.
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