1. Not finding help here? Sign up for a free 30min 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!

Can electric charge be enclosed ?

  1. Oct 16, 2004 #1
    Hi everybody

    I'm wondering if it is possible to enclose a relatively high electric charge in a non-conducting recipent (say plastic or glass -- macroscopic : centimeters) ?
    Is it possible technically ?
    if so, what is the limit amount of charge we can enclose ?
    if so, would the recipient stay uncharged externally : ie will the recipient attract opposite charges on its external surface OR will the global charge of the recipient stay different from 0 ?


    when I said "relatively high charges" I mean |q| > 10e-5
    Last edited: Oct 16, 2004
  2. jcsd
  3. Oct 18, 2004 #2
    To be much clearer:
    I meant an electrostatic charge (+ or -) that is in the center of a glass or plastic sphere: so that the overall charge of the object is not 0. I do not mean a capacitor as the overall electrostatic charge of capacitors is allways 0. Simply : an object that has (and won't lose) an overall electrostatic different from 0 (and in particular |q| > 1e-5),
    Can this be done (given current state of technology) ?
  4. Oct 19, 2004 #3
    You do not give units - do you mean 1e-5 coulomb? On a sphere 10 cm in radius the field at the surface would be 9e+6 V/m. Whether your charge configuration will be stable in the short run depends on the breakdown field of the insulator.

    Of course, things do get neutralized: corona, cosmic rays. After some time you will have a kind of Leyden jar with a compensating charge on the outside. In other words: a capacitor.

    A different limit is the mechanical strength of the material holding the charges together against their Coulomb repulsion. If a cluster or molecule gets too highly charged (by an Auger cascade for example), it will fly apart in fragments - a Coulomb explosion.

    PS: This seems off topic - what is the connection with quantum physics?
  5. Oct 19, 2004 #4
    Indeed, my question is pretty off topic, I'm sorry for that; but amongst the others, this sub-forum is the most suitable for it (I think)

    yes I meant a charge of 1e-5 coulomb,
    Assuming a sphere of 10 cm in radius made of glass, would it stand the field of 9e+6 V/m at its surface ? If not, is there any other insulator with high breakdown field that would stand it ?

    About the Leyden Jar effect, assuming that the sphere is in pseudo-vacuum (1e-6 torr inside a much bigger glass recipient), will we still have a capacitor after some time (concerning the little sphere, the external big recipient does not matter) ?

    Another silly question:
    In fact, I need some objects that will interact by great attraction or repulsion (1 to 10 Newton at a distance of 1 meter). That would be electrstatic charges or permanent magnets (neodymuim or other powerful ones). I think that force calculation and prediction for magnet is pretty complex (compared to electric charges). Besides, forces varies at 1/(r^3) for magnets.
    This explains my question.

    So here goes the silly new part:
    assuming a spherical capacitor (radius 10 cm) having in its center a charge +Q, and on the external surface another charge -Q, the global charge will be 0, just like a neutral atom.

    With all the shielding an insolation required, is there any configuration that will make the capacitor hold its charge for a very long time (1 year or longer), and more importantly, will this capacitor generate a net electric field outside the sphere (to have interactions between two capacitors).

    thank you very much for any help or remarks
    Last edited: Oct 19, 2004
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Can electric charge be enclosed ?
  1. Can you define charge? (Replies: 16)