Faraday's vs Ampere's Laws and current density

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Discussion Overview

The discussion revolves around the relationship between Faraday's and Ampere's laws, particularly in the context of electromotive force (EMF) and current density. Participants explore the implications of these laws in both theoretical and experimental scenarios, including the effects of varying frequencies and configurations in electromagnetic induction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Experimental/applied

Main Points Raised

  • One participant suggests that Faraday's Law indicates a time-varying magnetic field induces an electromotive force, which in turn produces an electric current density in a medium, and seeks confirmation on this interpretation.
  • Another participant notes that the current produced by EMF is contingent on the presence of a circuit, emphasizing that current density is influenced by both electric field (E) and resistivity.
  • A third participant comments on the mathematical representation of the relationship between electric field and magnetic field, affirming the substitution used in the equations presented.
  • A different participant shares experimental results involving a coil and solenoid, detailing the induced EMF at various frequencies and configurations, and expresses a need for recommendations regarding their findings.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of the laws discussed, and multiple viewpoints regarding the relationship between EMF, current density, and experimental outcomes remain present.

Contextual Notes

The discussion includes assumptions about circuit conditions and resistivity that are not fully explored. The experimental results shared by one participant introduce additional variables that may affect the interpretation of the laws in practice.

Who May Find This Useful

Individuals interested in electromagnetic theory, experimental physics, and the practical applications of Faraday's and Ampere's laws may find this discussion relevant.

VictorVictor5
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Greetings all,

I know that Faraday's and Ampere's law are related by M.E., but can I say the following?

By Faraday’s Law, a time varying magnetic field induces an electromotive force, which produces an electric current density in a media.

Up until EMF, that's Faraday's, but is the rest of the sentence true? I would assume yes since J=sigma*E, or E=J/sigma to keep it in line with using Del X E = -jwB, or Del X J/sigma=-jwB.

Just trying to confirm.

Thanks!
VV5
 
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The EMF can produce a current if there is a circuit. The current will depend on EMF and resistance. The current density will depend on E and resistivity.
 
On the right side of Del X E you would have the negative of the time derivative of B. The substitution for E looks fine.
 
Thanks to both!
 
hi
i have a coil of three turns and the spacing between the turns is 5 mm. i feed the coil with a signal of 13.24 MHz. and i put a solenoid of 3 mm radius 21 cm away from the coil to induce an emf. the solenoid has 23 number of tuns, 28 mm length. the induced emf is 280 mm V (rms) which is almost 10 times more than what i calculated. when i diconnect the coil from the signal generator, the induced voltage is 128 mmV(rms). the net emf= 152 mmVrms..
when the feeding freequency increased to 13.56 MHz and the solenoids number of turns decreased to 22. induced emf =460 mmV (rms) discennected 213 mmV. net induced emf=247 mV (rms).
can any recomand me any think.
thank you
 

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