Is back EMF equal to the induced EMF in self-induction?

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Discussion Overview

The discussion revolves around the concept of back electromotive force (EMF) in the context of self-induction, specifically questioning whether the back EMF is equal to the induced EMF when the current intensity increases gradually. The scope includes theoretical aspects of electromagnetism and the behavior of circuits under self-induction.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant asserts that in self-induction, an EMF is induced that generates a back current equal in magnitude and opposite in direction to oppose the increase in current.
  • Another participant introduces the distinction between instantaneous current and the rate of change of current, suggesting that these factors relate differently to magnetic flux and its change.
  • A participant challenges the claim about the back current being equal in magnitude, questioning the correctness of this assertion.
  • Further, a participant expresses uncertainty, stating they cannot think of any example where the back EMF is equal to the induced EMF.

Areas of Agreement / Disagreement

Participants express disagreement regarding the equality of back EMF and induced EMF, with some questioning the validity of the claim that they are equal in magnitude. The discussion remains unresolved with multiple competing views.

Contextual Notes

There are limitations in the discussion regarding the definitions of terms used, the assumptions about the conditions under which the EMF is considered, and the lack of examples to illustrate the claims made.

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In the case of self induction, when the intensity increases gradually an emf is induced which generates a back current " equal in magnitude, opposite in direction " to oppose the increase, so if that is right shouldn't the intensity in the coil Become ZERO till the intensity becomes steady?
 
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Well, there are two things going on here. There is the instantaneous current and then there is the rate of change of current. You have to think again at which one provides the magnetic flux and which one provides the change in flux.
 
ElmorshedyDr said:
an emf is induced which generates a back current " equal in magnitude, opposite in direction " to oppose the increase,
Where did you get the bolded part (equal in magnitude)? It is not correct.
 
Last edited:
DaleSpam said:
Where did you get the bolded part (equal in magnitude)? It is not correct.
So it doesn't have to be equal ?
 
I cannot think of any example where it is equal.
 

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