Who Performs Work in EMF Generation with Changing Magnetic Fields?

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Discussion Overview

The discussion revolves around the generation of electromotive force (EMF) in the context of changing magnetic fields, specifically addressing who performs work in this process and whether EMF can be generated through non-constant magnetic fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about who performs work in the generation of EMF when moving a closed loop of wire through a constant magnetic field.
  • Another participant asserts that the work is done by the person pushing or rotating the coil.
  • It is proposed that EMF can indeed be generated through a changing magnetic field without the need to rotate the coil, as the changing magnetic flux can induce EMF.
  • A later reply supports the idea that large generators or alternators operate by rotating a magnet on a shaft within fixed coils, indicating a practical application of changing magnetic fields to generate EMF.

Areas of Agreement / Disagreement

Participants generally agree that EMF can be generated through changing magnetic fields, but there is some uncertainty regarding the specifics of who performs the work in the process.

Contextual Notes

The discussion does not resolve the initial question of who is doing the work in the context of EMF generation, and assumptions regarding the definitions of work and EMF are not fully explored.

fricke
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I understand that EMF is generated by moving a closed loop of wire through a constant magnetic field. I am confused about one thing, who is actually doing work here? (of course it is not magnetic field).
 
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and one more question. Can EMF be generated through non-constant magnetic field? say, the magnetic field is changing with time.
 
Question 1: You are doing the work by pushing or rotating the coil.
Q2: Yes. If the magnetic field is changing with time, you don't have to rotate the coil. The changing magnetic flux induces an emf.
 
fricke said:
and one more question. Can EMF be generated through non-constant magnetic field? say, the magnetic field is changing with time.

yes, that's the way most large generators/alternators work. The magnet is rotated on a shaft inside the surrounding fixed coils

Dave
 

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