Please explain - total electic field Ec + En within the coils must be zero

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Discussion Overview

The discussion revolves around the concept of electric fields within coils of inductors, specifically addressing the assertion that the total electric field (Ec + En) must be zero in the context of applying Kirchhoff's rule. Participants explore the implications of this assertion and the definitions of the electric fields involved.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions why the sum of the conservative electric field (Ec) and the non-conservative electric field (En) within the coils should equal zero, seeking clarification on this assertion.
  • Another participant suggests that understanding the behavior of electric fields in conductors can be aided by reviewing Walter Lewin's lecture on induced electromotive force (emf), implying that it provides relevant insights.
  • A participant defines Ec as the conservative electric field based on Coulomb's law and En as the non-conservative electric field induced by changing magnetic flux.
  • There is a mention of the voltage drop across an inductor and the apparent contradiction between this voltage and the integral of the electric field along the coil wire, leading to a discussion on the small electric field within a good conductor.
  • One participant emphasizes the importance of Lewin's lectures in reconciling the relationship between L dI/dt and the integral of the electric field outside the coil.

Areas of Agreement / Disagreement

Participants express differing levels of understanding regarding the definitions and implications of Ec and En. There is no consensus on the reasoning behind the assertion that their sum must be zero, and the discussion remains unresolved.

Contextual Notes

Some participants note the need for further clarification on the definitions of Ec and En, as well as the conditions under which the electric fields are considered. The discussion highlights the complexity of analyzing electric fields in inductors and the assumptions involved in applying Kirchhoff's rule.

bksree
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Please explain -- total electic field Ec + En within the coils must be zero

Hi
This is from the text University Physics.
In pg. 1035, chap 10, in order to justify the use of Kirchoff's rule to analyze circuits containing inductors it is written :
Let's assume we are dealing with an inductor whose coils have negligible resistance. Then a negligibly small electric field is required to make charge move through the coils, so the total electic field Ec + En within the coils must be zero, even though neither field is individually zero.

The doubt is : Why should En + Ec be zero ?


TIA
sree
 
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I don't know what En and Ec mean, but I strongly recommend reading Walter Lewin's lecture on induced fem. He addresses the question why the electric field inside a good conductor should be very small.
 


Ec - conservative electric field (Couloumb's law)
En - non conservative electric field (induced field due to change in flux)
 


The voltage drop across an inductor, L dI/dt can be large. However, if you try to equal this figure to the integral of the electric along the coil wire you find a small number because, for any finite current, the field inside a good conductor must be very small.
How do you reconcile both points of view?
Walter Lewin shows how L dI/dt equals the integral of the electric field outside the coil.
I strongly suggest that you watch Lewin's lectures; they're free.
 

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