How to apply Faraday's Law of Induction

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Discussion Overview

The discussion revolves around the application of Faraday's Law of Induction in constructing a circuit to measure ambient magnetic field strength, specifically for detecting wires or assessing field levels above a certain threshold. The scope includes practical circuit design and theoretical understanding of electromagnetic principles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks clarification on how to apply Faraday's Law to measure the induced voltage in a 1mH inductor placed in a 0.5 Gauss magnetic field from a 60Hz power line.
  • Another participant suggests using the Hall Effect for measuring ambient magnetic fields, noting its applicability to DC currents but questioning its relevance for AC fields.
  • A third participant discusses the calculation of induced voltage using the formula n * dphi/dt, expressing uncertainty about the units involved and sharing their own experimental setup with a coil to measure induced voltage.
  • This participant also raises concerns about the use of iron cores in inductors due to potential flux concentration issues.
  • Participants share resources, including a recommendation for a book on magnetic measurements that may aid in understanding the topic further.

Areas of Agreement / Disagreement

Participants express differing views on the best approach to measuring magnetic fields, with some advocating for the Hall Effect and others focusing on Faraday's Law. The discussion remains unresolved regarding the most effective method and the specifics of the calculations involved.

Contextual Notes

There are uncertainties regarding the units of measurement in the context of Faraday's Law, as well as the assumptions made about the inductor's core material and its effect on the induced voltage.

HyTronix
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Greetings,

I have read the explanation on this forum here: https://www.physicsforums.com/showthread.php?t=441637 which discusses Faraday's Law of Induction, but I'm having a hard time understanding how to extrapolate that to my problem.

My goal:

Construct a circuit that measures ambient magnetic field strength, i.e., for finding wires, or determining if the ambient field strength is above a recommended (and likely arbitrary) background level of .5 Gauss.

I have a great deal of electronics experience, but, frankly, I'm terrible with math. Construction of the circuit is quite simple (I have a working spice model at any rate) but where Faraday's Law enters the picture is this:

-Assume the "probe" I've placed in this device is a 1mH inductor
-I'm expecting this probe to produce a voltage I can measure, likely in micro or millivolts

So, can anyone give me a working example that would help me understand this? For instance, if my 1mH inductor was placed into a field of .5G strength coming from a 60Hz power line, what voltage would be induced on the probe?

Thanks,

-John
 
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Google for Hall Effect. That effect is essence for measuring ambient magnetic fields, Concept is quite simple. Although that is for DC currents, I think it should apply somehow to AC.
 
aha magnetics is not well taught IMHO. n * dphi/dt is fine but what are the units?

i used ten turns on 14 inch diameter to give 0.1 square meter coil
so the voltage induced was direct indication of omega * (d phi/dt), flux in webers/m^2 which is 10,000 gauss.. at 60 hz w is 377 so next time i might make the coil 1/3.77 square meters.

i hope i have units right...

if your 1mh inductor is air core it might work but i wouldn't trust an iron core for fear it'll concentrate flux.

you need this book
http://books.google.com/books/about/The_magnetic_measurements_handbook.html?id=byy_GwAACAAJ

it's great. i built his fluxgate magnetometer.
 
Thanks to both of you. I'll definitely grab a copy of that book.

-John
 

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