Do electric fields in a conductor go to zero in all instances?

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Discussion Overview

The discussion centers around the behavior of electric fields within conductors, particularly whether the electric field can ever be non-zero and the conditions under which it is canceled. Participants explore theoretical, experimental, and mathematical perspectives on this topic, including implications for real-world materials and superconductors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asserts that in the absence of external forces, the electric field inside a conductor should go to zero due to the movement of charges canceling any existing field.
  • Another participant claims that a charge distribution that cancels the electric field always exists and is unique, referencing theorems related to boundary value problems for Poisson's equation.
  • A different viewpoint suggests that if charges were in constant motion, they would radiate energy, leading to a need for constant velocities, which may not be feasible in real materials.
  • One participant raises the possibility of an extremely strong electric field that could exceed the available charge distribution to cancel it, speculating on potential ionization or breakdown of the material.
  • Another participant points out that while the electric field in a perfect conductor at equilibrium is zero, real conductors are not perfect, and some field may always be present unless in perfect equilibrium.
  • A later reply questions the notion of constant motion in materials, bringing superconductors into the discussion as examples of systems that can maintain circulating currents without energy loss.

Areas of Agreement / Disagreement

Participants express differing views on the existence and uniqueness of charge distributions that can cancel electric fields, as well as the implications of constant motion of charges in conductors. The discussion remains unresolved regarding the conditions under which electric fields may not go to zero in all instances.

Contextual Notes

Participants note limitations related to the definitions of perfect conductors and the assumptions underlying the behavior of charges in real materials, including the need for perfect equilibrium and the effects of strong electric fields.

BucketOfFish
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In the absence of external forces, the electric field inside a conductor is supposed to go to zero. This is because if any field were to exist, then the charges in the conductor would experience force and continue moving until they canceled the field.

However, is it true that for any system a certain charge distribution always exists which can successfully cancel all electric field? Could it not be the case that no such configuration exists, forcing the surface charges to remain in constant motion?

Are you aware of any experimental, physical, or mathematical explanation as to why field should always be cancelled?
 
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As far as I understand, such a charge distribution (a) always exists; and (b) is unique. This is a boundary value problem for Poisson's equation and existence and uniqueness of solutions (given completely specified boundary conditions) is a theorem.
 
If the charges in constant motion accelerated, they would radiate away energy, causing their motion to eventually dampen down. Therefore, particles in perpetual constant motion would need to have constant velocities, which is impossible in a real, finite, material.

In principle, you could have an electric field that was so strong, there simply weren't enough charges available to fully cancel it out. This would be a stationary equilibrium. In practice, I'd imagine you'd have some sort of ionization or breakdown in the material, although that's just a shot in the dark.
 
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Thanks for the answers! Leveret, you say that it's not physical to have particles in constant motion in a material, but from what I know about superconductors, they can hold constantly circulating currents for very long periods of time without any energy input. Do you know what is happening in that instance?
 
More accurately: The electric field in a perfect conductor at equilibrium is zero. There are no perfect conductors in real life, so the field always pokes in a bit. But this is an excellent approximation for many conductors. Also, you have to have perfect equilibrium to give all the excess charge time to migrate to the surface.

"However, is it true that for any system a certain charge distribution always exists which can successfully cancel all electric field?" That's the definition of a perfect conductor. If it couldn't provide the free charge to cancel the fields it would not be a conductor.
 

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