I have been trying to understand why the net electric field inside a conductor is zero regardless of the exterbal electric field. But why should equilibrium ever be attained?
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2It is not necessarily zero. If there's any current, such as a current-carying wire, the E field is definitely not zero! It is only in electrostatics that the E field vanishes inside a conductor. Because if it wasn't zero, the charges would move. – untreated_paramediensis_karnik May 22 '19 at 18:28
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See the diagrams below.
The top diagram shows a conductor with no external field applied. Note that the charges are randomly distributed within the conductor. Since there is no external field there is no field within the conductor as well.
The bottom diagram shows the same conductor in the presence of an constant external field perpendicular to the length of the condutor. By convention, the direction of the electric field is the direction of the force that a positive charge would experience if placed in the field. So the free electrons inside the conductor experience a force moving them to the left side of the conductor leaving the right side of the conductor positively charged. The charges have rearranged themselves until they no longer experience a force. Bottom line, equilibrium is established within the conductor.
Now note the direction of the electric field within the conductor. It is equal and opposite to the direction of the field external to the conductor. Keep in mind that the external field passes through the conductor. So there a net field within the conductor of zero.
If the external field were parallel to the conductor and the conductor was part of a closed circuit, current would flow in the conductor.
Hope this helps.
Bob D
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perhaps,I need to know,why should charges be at equillibrium when no ext.electric field is applied at the first place?why wouldn't they move and move around the conductor and never reach equillibrium?,I know it might violate energy conservation,but how do we know that there is not any configuration or shape of conductor in which equillibrium is never reached? – Dheeraj Gujrathi Apr 25 '23 at 06:54
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@DheerajGujrathi The electrons are in constant random thermal motion, with or without the electric field present. It just that there is no collective motion in any particular direction in the absence of an electric field. – Bob D Apr 25 '23 at 11:09
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rephrasing my doubt,When we say "The charges have rearranged themselves until they no longer experience a force",what if this rearrangement takes forever?what if they try to rearrange but find no structure in an odd shaped conductor where equillibrium cannot be established?how do we know all conductors will cause equillibrium? – Dheeraj Gujrathi Apr 25 '23 at 11:55
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Are you questioning that everything tends to equilibrium or just how long it takes? Also, I don't understand what you mean by "conductors will cause equilibrium "(?) – Bob D Apr 25 '23 at 12:07
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yes,I am trying to ask,why is the equillibrium necessary?by"conductors will cause equillibrium" I mean to ask,can there be a shape of conductor where no charge distribution of electrons can lead to equillibrium of electrons? – Dheeraj Gujrathi Apr 25 '23 at 12:20
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