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capacitor basics

Discussion in 'Electronic Basics' started by [email protected], Oct 14, 2005.

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  1. Guest

    sir,

    I have a dout about capacitor discharge.Can a charged capacitor
    discharge by connecting its one terminal and ground without using its
    other terminal.
     
  2. Bob

    Bob Guest

    The only way to reduce the voltage of a so-called charged capacitor is by
    providing a conductive path between the two terminals of that capacitor.

    Earth, or ground is only conductive to other parts of the earth (and rather
    poorly). People sometimes refer to a common point in a circuit as "ground".
    A circuit's "common" only has a conductive path to real ground (earth) if
    it's connected to ground (earth).

    Bob
     
  3. Guest

    Sir,
    If we touch one terminal of the charged capacitor , is current flow
    through our body to the ground without any contact with other terminal.
     
  4. Robin

    Robin Guest

    Can you pull a cork out of a bottle one-handed?
    No you *have* to use the other hand to hold the bottle.

    Likewise the capacitor can only push as much current out of one
    terminal as it pulls into the other.
     
  5. Andrew Holme

    Andrew Holme Guest

    In electrostatics, you can discharge a body by providing a conductive
    path to earth (or anywhere else); but a capacitor is two charged bodies
    (plates), holding equal and opposite charges, with an electric field
    between them. If you connect a conductive path to one plate, only a
    very small percentage of the stored charge will re-distribute itself.
     
  6. Andy Baxter

    Andy Baxter Guest

    Robin said:
    yes - you put the corkscrew in, tie it to a long piece of string, and then
    whirl it round very-very-fast... ;)
     
  7. Andy Baxter

    Andy Baxter Guest

    anilmanual said:
    Sir,

    You now have a scientific hypothesis on your hands. Namely that you can
    discharge a capacitor by touching only one of its terminals to the ground.
    The thing to do with scientific hypotheses is to test them, so think of a
    way to do so and try it yourself.
     
  8. Kitchen Man

    Kitchen Man Guest

    Sir, "current flow" is a misuse of terms, and circuits are circular.
     
  9. Rich Grise

    Rich Grise Guest

    Yabbut, that doesn't work with electrons. (Or, if you're a college boy,
    raised on "conventional current", the holes. ;-P )

    Good Luck!
    Rich
     
  10. Jasen Betts

    Jasen Betts Guest

    not unless the other terminal is connected to ground (or to something that
    connected to ground etc...)

    except, some capacitors leak charge but that is a slow discharge process.

    Bye.
    Jasen
     
  11. Jasen Betts

    Jasen Betts Guest

    If nothing is touching the other terminal no current will flow through the
    one you touch.

    Bye.
    Jasen
     
  12. Guest

    Sir,
    What is situation in case of lightning .ie lot of electrons are going
    to ground...could u pls tell me the actual process of lightning ....
     
  13. In that case, you and the lightning are inside the capacitor, made up
    of the ground as one plate and the cloud as the other plate, with the
    air between being the dielectric.
     
  14. Bill Bowden

    Bill Bowden Guest

    The only way to reduce the voltage of a so-called charged capacitor is by
    There is a way to reduce the capacitor voltage without a conductive
    path. You can add more dielectric, which will increase the capacity,
    and reduce the voltage.

    -Bill
     

  15. You forgot to mention that the capacitor is over its rated voltage
    when it arcs over. ;-)
     
  16. Golly! So it is.
     
  17. Jasen Betts

    Jasen Betts Guest

    That'll increase the voltage unless the dielectric is a gas and the plates
    aren't moving apart to accomodate the extra dielectric.

    to reduce the voltage move the plates closer together.
     
  18. Tim Williams

    Tim Williams Guest

    Eh? He means increasing the effective area of the plates. Not increasing
    thickness.

    Tim
     
  19. Jamie

    Jamie Guest

    actually, i think it's the other way around but then again, i could be
    wrong :)
    i think they actually travel from the ground up and when the path
    is complete you then get an ionized stream which acts like a short
    circuit that gives you that nice little light show ect..
     
  20. Robin

    Robin Guest

    No, as originally stated, the voltage will *decrease* with "more
    dielectric".

    This is because the dielectric is "stretched" and *that* absorbs energy
    hence the voltage must drop a little because energy is conserved. See
    Feynman's Lectures on Physics volume 2 chapter 10 section 3.

    Also see chapter 9 for fascinating (non technical) description of
    lightning.

    Cheers
    Robin
     
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