Magnetic Field of an AA Battery 'Immersed' in a Conductor

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Discussion Overview

The discussion revolves around the theoretical implications of placing an AA battery in an ideal conducting medium, referred to as an 'ether.' Participants explore questions regarding current flow, the resulting magnetic field, and interactions with external magnetic fields. The scope includes conceptual and theoretical considerations rather than practical applications.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question the definition of an "ideal conducting ether," suggesting that without a clear definition, the questions posed may not make sense.
  • One participant proposes that water could serve as a "conducting ether," though it is acknowledged that it is not a very good conductor, and impurities play a role in its conductivity.
  • Another participant suggests that the thought experiment could be framed as placing the battery in a thick-walled tubular conductor, prompting further exploration of the model.
  • There is a discussion about the flow of electrons in a hypothetical saltwater pool surrounding the battery, with speculation that the flow would be symmetric and most intense near the battery.
  • Some participants reference the Biot-Savart Law to argue that there must be a magnetic field generated by the current flow, despite some claims that the magnetic field could be zero under certain symmetrical conditions.
  • There is a debate regarding the implications of Maxwell's equations, particularly Ampère's circuital law, with some participants asserting that the magnetic field must be zero if the total electric current enclosed by a magnetic loop is zero, while others challenge this by suggesting that the field is non-zero at smaller scales.

Areas of Agreement / Disagreement

Participants generally do not reach consensus on the nature of the ideal conducting ether or the implications of the magnetic field generated by the battery. Multiple competing views remain regarding the behavior of current and magnetic fields in this theoretical scenario.

Contextual Notes

Limitations include the undefined nature of the "ideal conducting ether," assumptions about symmetry in the arrangement, and unresolved mathematical interpretations of Maxwell's equations and their implications for the magnetic field.

Fibonacci Vonacci
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If an AA battery were placed in some kind of ideal conducting 'ether':

1) Would current flow, and if so, what would the flow of electrons look like?

2) How would the magnetic field look? (I imagine that if there was an electric current flowing, that the magnetic field would look a little like the magnetic field of the earth)

3) If placed near another magnetic field would the battery 'roll' towards the new source?
 
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Fibonacci Vonacci said:
some kind of ideal conducting 'ether':

what is that ??
without being able to define this mythical substance, none of the rest of your questions make any sense
 
davenn said:
what is that ??
without being able to define this mythical substance, none of the rest of your questions make any sense

I do not have enough knowledge to define such a substance, so perhaps I can ask it in a different way, starting with a first step.

As a thought experiment, is it theoretically conceivable that a substance could exist with the properties that it could surround a battery allowing current to flow through itself?
 
Water could be considered a "conducting ether" just not a very good one.
 
CWatters said:
Water could be considered a "conducting ether" just not a very good one.

Yes indeed, in water it is the impurities that conduct electricity. I'm hoping to grasp what an ideal conducting medium might act like in this model, so I suppose 'ideal' needs some clarification. To my beginner's mind this might mean that the electrons are free to move in any direction, so that resistance is uniform.

I appreciate that what I asked may be absurd, but when asking it I do not know enough to know why it is absurd.
 
Ok so I think this is like putting the battery in a thick walled tubular conductor with the paper wrapper on the battery forming a void. So perhaps see some of the digrams here...

https://www.nde-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/CircularFields.htm
 
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CWatters said:
Water could be considered a "conducting ether" just not a very good one.

Add some salt.

fig1.jpg
 

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Fibonacci Vonacci said:
1) Would current flow, and if so, what would the flow of electrons look like?

Let the battery be in the middle of a large saltwater pool. The flow will be symmetric about the axis of the battery? The flow will be most intense near the battery? Far from the battery the flow is small but not zero?

What is the differential form of Ohm's law for 3 dimensional conductors like our case above?

Thanks!
 
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Fibonacci Vonacci said:
If an AA battery were placed in some kind of ideal conducting 'ether':

1) Would current flow, and if so, what would the flow of electrons look like?

2) How would the magnetic field look? (I imagine that if there was an electric current flowing, that the magnetic field would look a little like the magnetic field of the earth)

3) If placed near another magnetic field would the battery 'roll' towards the new source?
Looks like a coaxial cable, so nothing on the outside.
 
  • #10
tech99 said:
nothing on the outside

There will be current flow at large distances from the battery unlike a coax cable. Using this fact and the Biot-Savart Law you can show there must be a magnetic field.
 
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  • #11
If the whole arrangement is perfectly symmetric the magnetic field would also have to be symmetric around the battery. But according to maxwell's equations - more specifically Ampère's circuital law - that field needs to be zero here since the total electric current enclosed by the magnetic loop is zero.
 
  • #12
DrZoidberg said:
the total electric current enclosed by the magnetic loop is zero.

Only if the loop is very large will the total current through the area of the loop be zero.
 
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  • #13
upload_2017-11-26_6-20-54.png
 

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  • #14
DrZoidberg said:
If the whole arrangement is perfectly symmetric the magnetic field would also have to be symmetric around the battery. But according to maxwell's equations - more specifically Ampère's circuital law - that field needs to be zero here since the total electric current enclosed by the magnetic loop is zero.

DrZoidberg, could you expand on this a little bit please? I'm struggling to understanding why the field needs to be zero.
 
  • #15
Look at Spinnor's drawing. The field strength approaches zero if the loop is very large. Otherwise it's non zero.
 

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