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I apologies if my wording is bad or it is duplicate.

  • I'm new to Electrostatics. During the topic of conductors & electric field I was introduced to Electrostatic Equilibrium state in which the distribution of all electrons in a conductor is complete and they is no more movement.

  • I understand this state will influence 0 electric field inside the conductor.

  • Then the author says that using this concept we can surround ourself with a conductor and it will prevent us from all electric fields influnced to conductor from outside.

  • But let's assume an ideal world where intially there was no other charges other that 2 difrent systems, 1 insulator and 1 conductor.

  • We put the insulator inside the conductor. And after some time they will reach the point when both electric field cancels out and creates the state of Electrostatic Equilibrium.

  • Now assume we bring an another charge from outside of the conductor.

  • Conductor will influence the new charge electric field; And electrons will again redistribute themself.

  • My question is that during the second redistribution wouldn't the insulator influence the electric field as the conductor's initial equilibrium is broken.

One possible answer I think would be that being conductors have high conductivity ie. electrons move faster inside conductor, the time to re-achieve equilibrium would be so fast that the change in electric field would be negligible.

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Electrostatics problems do not consider cases where charges are moving. They are valid problems, but more complex. So you have one electrostatic problem. You add a charge and wait again for equilibrium. Then you have another electrostatic problem.

You are right that electrons redistribute themselves very quickly in a conductor. If you pushed a charge with your hand, they would stay very close to equilibrium, and you could think of it as continually in equilibrium. But when charges are pushed around by electric fields, they can move very quickly. In that case, you might not have equilibrium.

Another non equilibrium case is when you have a current flowing in a circuit. Even though charges might flow slowly, they flow continually. There is an electric field inside a wire pushing charges along.

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  • $\begingroup$ So in the sense Faraday's cage just stop getting electric field from getting out. And it is just fast enough for outside disturbance to go unnoticed. $\endgroup$
    – user380217
    Commented Nov 28, 2023 at 16:36