Difference in potential induced by a magnetostatic field? O_o

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Discussion Overview

The discussion revolves around the observed difference in electric potential between a stationary magnet and a conductor placed underneath a dielectric material. Participants explore the implications of magnetostatic fields and their interactions with dielectrics and conductors, questioning the mechanisms behind the induced potential differences.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes a potential difference of up to 0.5 volts when measuring between a stationary magnet and aluminum, but finds the potential difference drops to zero when the magnet or dielectric is removed.
  • Another participant questions whether the potential difference is a DC potential or a transient pulse and mentions the input impedance of the voltmeter as a factor in the measurements.
  • A later reply confirms that the potential difference reverses when the magnet is flipped over and that it works with different metals, such as aluminum and copper.
  • One participant speculates that the dielectric materials might influence the magnetostatic field, potentially creating a time-varying field, but expresses uncertainty about this explanation.
  • There is a suggestion to consider the effects of stray magnetic fields on analog voltmeters with D'Arsonval movements.

Areas of Agreement / Disagreement

Participants express various hypotheses regarding the nature of the potential difference and its dependence on the configuration of the materials involved. There is no consensus on the underlying mechanisms or the implications of the observations made.

Contextual Notes

The discussion includes uncertainties regarding the definitions of potential types (DC vs. transient) and the influence of dielectric materials on the magnetic field, which remain unresolved.

Vectronix
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Hi,

Why is there a difference in electric potential from a point on the surface of a stationary magnet to a point on a conductor that is placed underneath a dielectric? I placed some stationary magnets on top of glass or a piece of paper and put some aluminum under it, and touch one end of a voltmeter to the magnet and the other end of the voltmeter to the aluminum, the most I got was like 0.5 volts. When I remove the paper the potential difference is zero. If I remove the magnet, the potential difference is zero. When I have the magnet there at rest on top of the paper, which is above the aluminum, the potential difference is nonzero. When I start moving the magnet and the paper away from each other, the potential difference starts dropping quickly.

I thought that only a magnetic flux that is changing could induce a difference in potential. Anyone got an idea what's going on here?
 
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Hi Vectronix! Welcome to PF! :smile:
Vectronix said:
Hi,

Why is there a difference in electric potential from a point on the surface of a stationary magnet to a point on a conductor that is placed underneath a dielectric? I placed some stationary magnets on top of glass or a piece of paper and put some aluminum under it, and touch one end of a voltmeter to the magnet and the other end of the voltmeter to the aluminum, the most I got was like 0.5 volts. When I remove the paper the potential difference is zero. If I remove the magnet, the potential difference is zero. When I have the magnet there at rest on top of the paper, which is above the aluminum, the potential difference is nonzero. When I start moving the magnet and the paper away from each other, the potential difference starts dropping quickly.

I thought that only a magnetic flux that is changing could induce a difference in potential. Anyone got an idea what's going on here?

That's interesting … does anyone else know the answer? :smile:

(btw, does the potential difference reverse if you turn the magnet over? and does it work with other metals?)
 
Hi Vectronix-
This is a very good question, as is the suggestion by tiny-tim-
Are you talking about a dc potential, or a transient pulse (like discharging something). What is the input impedance of your voltmeter? If is something like 20 megohms. and the distributed capacitance is certainly less than a nanoFarad, then the transient would be less than RC = 0.02 seconds. You also told us that there is no dc circuit (loop), so there can be no current, or contact potential. So it is a puzzle.

By the way, do you happen to have an analog voltmeter with a D'Arsonval movement? See
http://www.engineersedge.com/instrumentation/electrical_meters_measurement/darsonval_movement.htm
Is it affected by stray magnetic fields?
Bob S
 
Hey, muchachos. :)

I'm sorry, I have been busy for a while, and I wasn't able to get to this sooner. Yes, the potential difference reverses when I flip the magnet over. It is a DC potential, not a transient pulse. The voltage started off at a certain level then it decreased some and stabilized after a short while when I did this. Yes, it works with different metals. I tried aluminum and copper.

I was thinking that maybe the dielectric that I use (paper, glass, etc.) and probably every other dielectric and its electric fields influence the magnetostatic field of the magnets I use thus becoming a time-varying field (changing magnitude and/or direction). But I am not sure why, if that is true. Any thoughts on this explanation? Anything to add to it? I will answer the other questions soon.
 
Vectronix said:
I'm sorry, I have been busy for a while, and I wasn't able to get to this sooner. Yes, the potential difference reverses when I flip the magnet over. It is a DC potential, not a transient pulse. The voltage started off at a certain level then it decreased some and stabilized after a short while when I did this. Yes, it works with different metals. I tried aluminum and copper.

I was thinking that maybe the dielectric that I use (paper, glass, etc.) and probably every other dielectric and its electric fields influence the magnetostatic field of the magnets I use thus becoming a time-varying field (changing magnitude and/or direction). But I am not sure why, if that is true. Any thoughts on this explanation? Anything to add to it? I will answer the other questions soon.
Hi Vectronix-
Did you know that analog meters with D'Arsonval movements have moving magnets inside? Keep your magnets far away from these meters.
Bob S
 

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