Electric Field Inside A Wire

nikolafmf

Homework Statement

Griffiths says in his "Introduction to Electrodynamics" that electric field within a conductor is 0, but isnide a wire is different from 0. Since wire is also a conductor, how can that be possible? And how to calculate electric field inside a wire? Wire has resistivity [tex]\rho[/tex], radius a and current I trough information technology.

Homework Equations

Due east= 0 inside a conductor;
Eastward = [tex]\frac{I\rho}{\pi a^2}[/tex]z (How to calculate this?)

The Attempt at a Solution

Have no idea how to showtime...

ideasrule

The wire is not a perfect usher. A perfect conductor has 0 resistivity, which implies no electric field via your 2nd equation.

nikolafmf

Thank you ideasrule for your response. Whatsoever idea how to calculate field in a wire and go my second equation?

Doc Al

Griffiths says in his "Introduction to Electrodynamics" that electric field inside a conductor is 0, but isnide a wire is different from 0. Since wire is likewise a conductor, how tin that be possible?

The electric field is zero inside a conductor just in the electrostatic case. If you have a current in a wire, then you tin can certainly accept a non-zip electric field.

nikolafmf

The electrical field is nix within a conductor only in the electrostatic case. If you have a current in a wire, and then you can certainly take a non-zilch electric field.

Yeah, it should exist expected the field to prepare electrons in motion, or...? And how does this fields comes hither in nonelectrostatic case?

nikolafmf

So, the question here arises is under what weather is electrical field inside a usher nil and when is it nonzero? And why? Griffiths but explains that when we put usher in an outer electric field, the field within is still naught, as is null without outer field. Then if there is electric current, the field is every bit in second equation. Merely he doesn't explain this.

aim1732

The basic question you go out unanswered is why does the field become aught inside an ideal conductor.It does not do that instantly.The external field sets charges in motion which,gratis to move,set upwards an electric field that exactly cancels the applied field.That takes time although that is measured on the nano scale.

In a wire the charges exercise not accumulate---necessary for setting up an electric field.The charges keep moving--drifting--to prepare upwardly a current and not a field of their ain. If you lot read good books such every bit Resnick-Halliday information technology will say that field within is zero for an ideal ISOLATED usher.

yungman

The electric field is zero within a conductor only in the electrostatic case. If y'all have a current in a wire, then you can certainly have a not-nil electric field.

i thought East is always 0 in a perfect conductor regardless of electrostatic or electrodynamic. Whatever field inside will immediately crusade electrons to move in direction to cancel the field.

I sympathize about imperfect conductor have longitudinal East/B] and skin effect and all, but not with perfect conductor.

tiny-tim

Any field inside will immediately cause electrons to move in direction to cancel the field.

they'll only cancel the field if yous don't replenish it!

as Doc Al says …

The electric field is zippo within a usher only in the electrostatic case. If y'all have a electric current in a wire, then you tin certainly have a non-zero electric field.

so yes, a field within will immediately cause electrons to movement, but if you lot continue the field going (eg by using a bombardment), then the electrons will never abolish it!

Doc Al

i thought E is e'er 0 in a perfect usher regardless of electrostatic or electrodynamic. Any field within will immediately cause electrons to motion in management to abolish the field.

Yes, you are correct for a perfect conductor. Simply I thought we were talking about ordinary imperfect conductors, such as a copper wire. In such a case you can certainly have a non-zero field within the usher to bulldoze a current (every bit you lot well know).

aim1732 gave an fantabulous answer, which I agree with. (And I apologize to the OP for forgetting about this thread and non giving a more complete answer myself.)

To nikolafmf: To get your second equation, recollect of it as beingness equivalent to Ohm'south law.

(Didn't see you sneak in there, tiny-tim. )

Electric Field Inside A Wire