1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electric charge on conductors , capacitors

  1. Nov 14, 2013 #1
    Hi I'm wondering why does the charge resides on the plates on a capacitor when it's charged but not on say two closely placed wires or circuit traces etc, well I do understand that charges stay on capacitor plates because the opposite charges tend to attract and with a distance between them they stay as close as possible for as long as possible.

    So the question is more like , given the same amount of voltage does the charge accumulation depends on the conductor geometry or spacing between them ?
    Say I have a parallel plate capacitor and two wires with the surface area the same as that of the plates , and the gap between each of the wires just as big as that of the plates will they ahve the same capacitance or no?



    P.S. although I think it's impossible but would it be possible to make a capacitor which looses it's charge right after the source or the supply is taken away , well it wouldn't be a capacitor anymore but still , say I needed a device with which I can use + charge to attract some negative charge on the other plate but let it go just as when I disconnect the positive charge ?
    As upon disconnecting a capacitor it would discharge slowly.
     
  2. jcsd
  3. Nov 14, 2013 #2

    davenn

    User Avatar
    Science Advisor
    Gold Member

    the 2 "parallel wires of a circuit will have a charge on the for as long as there's a voltage applied
    Remove the voltage and the charge will dissipate out into the attached circuitry

    yes of course it is possible ... you just make a capacitor that has a very leaky dielectric between the plates so that current (charge) flows between the plates and balances out.
    This of course would be a VERY poor capacitor

    Dave
     
  4. Nov 14, 2013 #3
    Two wires laying next to each other will have a small but non-vanishing capacitance that indeed depends on the exact geometry of the wires such as their sizes and distances. That means that small but non-vanishing charges might indeed build up in those wires. For most purposes these charges can be considered negligible (but not always). Excellent question.
     
  5. Nov 14, 2013 #4
    @davenn , well yes a poor capacitor would do , but the problem is I need a good isolation between the plate so no current (in theory) runs between them but so that when I switch the negative potential off of one of the plates the + doesn't linger on the other as it would normally do.
    The purpose is so that I could switch a negative potential on the legs of two capacitors in series so that i could get charges to run back and forth between them.
    The thing is with a normal capacitor I can't do that just because the cap needs to be discharged or drained to ground for it to reverse polarity.

    @dauto , why would that be an excellent question , just asking ? :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Electric charge on conductors , capacitors
  1. Electrical conductors! (Replies: 2)

  2. Capacitor charging (Replies: 7)

  3. Charging a capacitor (Replies: 19)

Loading...