# Seeing both B field lines and E field lines at the same time

• B
• Rev. Cheeseman
In summary, the conversation discusses the possibility of seeing both electric and magnetic field lines at the same time by swapping nails with bar magnets. The resulting field lines would be a combination of both fields, however, it is difficult to accurately map both fields on a 2D diagram. It is also mentioned that charging and discharging bar magnets may not be effective and that magnetized materials are worse conductors.
Rev. Cheeseman
TL;DR Summary
What will we see if we make two bar magnets as the conductors inside an electric field?
After watching this clip Electric Field Lines Lab I wonder if it is possible to see both electric field lines and magnetic field lines at the same time by swapping the two nails in the video with two bar magnets, as the conductors as we understand bar magnets are metals and metals are good conductors of electricity. Here the resulting electric field lines from the same previous clip we can see the electric field lines. This image https://images.ctfassets.net/vrrt8f...99a9/Magnetic_field_of_a_Bar_magnet_art_4.svg shows magnetic field lines between two bar magnets with unlike poles pointing to each other. We see magnetic field lines with sprinkling iron filings around them. If we connect the positive and negative charge from a 9V battery to each of the bar magnets, will the electric field messes up the magnetic field lines? I'm trying to do this experiment but there is nothing available right now. I hope someone with enough materials can emulate this experiment.

If we combine both of the electric field lines picture and the magnetic field lines picture, the electric field lines and magnetic field lines run parallel to each other especially at the center or will they combine into one?

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A 2D diagram cannot map both the perpendicular E and M fields at the same time.
If you convert one, then attempt to map both at the same time, the result will be neither, but the sum of the two.

2D electrical field mapping can generate electrical analogs of magnetic fields by arranging the position of sources and equipotential boundaries.

Baluncore said:
A 2D diagram cannot map both the perpendicular E and M fields at the same time.
If you convert one, then attempt to map both at the same time, the result will be neither, but the sum of the two.

I wonder what that will looks like if it is 3D. Do you have any clue? So, in two-dimensional image, the electric field and magnetic field did run parallel if we make two bar magnets as the conductors in an electric field?

So, the resulting field lines will be a combination of electric field and magnetic field. What does that means? They become one or still separated?

Baluncore said:
2D electrical field mapping can generate electrical analogs of magnetic fields by arranging the position of sources and equipotential boundaries.

Thus, we can shape the electric field lines and magnetic field lines according to our own likings or what?

The way we try to find magnetic field lines is different from finding electric field lines like what we saw in the clip. We need iron filings or compasses to see the magnetic field lines. So, in order to see both field lines, first we need to do the first thing like in the clip and then when we swapped the nails with two bar magnets as the conductors we will need to use iron filings to see the magnetic field lines.

I think your proposed setup is two bar magnets with unalike poles facing each other separated by some distance. You then connect the magnets to the terminals of a battery, but not to one another, so you charge each one, rather than run a current through them.

I suspect charging and discharging your magnets won't do them much good, and I think magnetised materials are worse conductors than the same material unmagnetised, so actually doing this may be a bit more challenging than you think. Or it may not - I don't know the magnitude of either effect.

I would expect the resulting electric and magnetic fields to be similar. They won't be exactly the same, because the E field is roughly a dipole field while the B field is roughly the superposition of two dipole fields. But they'd be similar.

I suspect @Baluncore is imagining running a DC current through a bar magnet rather than charging two of them. That would just give you a magnetic field that's probably a bit messy to describe.
wonderingchicken said:
So, the resulting field lines will be a combination of electric field and magnetic field. What does that means? They become one or still separated?
No, it just means you have an electromagnetic field with both magnetic and electric components.

Ibix said:
I suspect @Baluncore is imagining running a DC current through a bar magnet rather than charging two of them.
That is interesting. I never thought of that.

Ibix said:
I think your proposed setup is two bar magnets with unalike poles facing each other separated by some distance. You then connect the magnets to the terminals of a battery, but not to one another, so you charge each one, rather than run a current through them.

I suspect charging and discharging your magnets won't do them much good, and I think magnetised materials are worse conductors than the same material unmagnetised, so actually doing this may be a bit more challenging than you think. Or it may not - I don't know the magnitude of either effect.

I would expect the resulting electric and magnetic fields to be similar. They won't be exactly the same, because the E field is roughly a dipole field while the B field is roughly the superposition of two dipole fields. But they'd be similar.

I suspect @Baluncore is imagining running a DC current through a bar magnet rather than charging two of them. That would just give you a magnetic field that's probably a bit messy to describe.

No, it just means you have an electromagnetic field with both magnetic and electric components.

So, the person in this clip Electric Field Lines Lab (click on the highlighted link on the left to watch the clip) was charging the nails rather than running a current through them? What's the result if we run a current through the bar magnets? Are the results different? What will the field lines look like?

I think magnetised materials are worse conductors than the same material unmagnetised

Maybe because unmagnetized material has no north/south pole.

The nails provided points of fixed potential, that made a current source and a sink. The current flowing in the sheet generated a potential field, that was then mapped as equipotentials. Perpendiculars were then drawn to show the direction of current flow, and so the electric field on the sheet.

Baluncore said:
The nails provided points of fixed potential, that made a current source and a sink. The current flowing in the sheet generated a potential field that was then mapped as equipotentials. Perpendiculars were then drawn to show the direction of current flow, and so the electric field on the sheet.

Therefore, the result if we use bar magnets as the conductors instead of nails will be like :
Ibix said:
I would expect the resulting electric and magnetic fields to be similar. They won't be exactly the same, because the E field is roughly a dipole field while the B field is roughly the superposition of two dipole fields. But they'd be similar.

Is that it?

wonderingchicken said:
Therefore, the result if we use bar magnets as the conductors instead of nails will be like :
That will depend on the length and the orientation of the conductive bar magnet. You could use the magnets as nails, or lie them on the surface as electrical equipotentials or field boundary conditions.

Baluncore said:
The nails provided points of fixed potential, that made a current source and a sink. The current flowing in the sheet generated a potential field, that was then mapped as equipotentials. Perpendiculars were then drawn to show the direction of current flow, and so the electric field on the sheet.
Perhaps I'm not understanding the setup, then. I thought the nails were just a (bad) capacitor, so no current flows after the initial charging. I'll look again later. It would help if @wonderingchicken described the setup and/or drew it, rather than saying "go and watch videos where they do something similar to what I want to do".

Ibix said:
Perhaps I'm not understanding the setup, then. I thought the nails were just a (bad) capacitor, so no current flows after the initial charging. I'll look again later. It would help if @wonderingchicken described the setup and/or drew it, rather than saying "go and watch videos where they do something similar to what I want to do".

The materials that person used in the video are a clear plastic container, a 9V battery, alligator clips, two nails as the conductors, a voltmeter, two graph papers with one of them is used to draw the electric field lines and some water.

First he put a graph paper underneath the plastic container. Then, he put the two nails with each nails on the farthest right and left on the plastic container by using a tape. Next, he connect the 9V battery to each of the nails with some alligator clips with the nails on the right is charge positive and the left is negatively charge. After that, he put 1 to 2 cm of water to the container and then he take a voltmeter and he connect the negative wire of the voltmeter to the negative part of the battery and he then plays around with the positive wire of the voltmeter by pointing it to various places on the plastic container to find the equipotential lines. He used the other graph paper (remember he used two graph papers in this experiment with the other one being underneath the clear plastic container) to write off the volt numbers of the charge or equipotential lines. Finally, after finishing finding the equipotential lines he then make the electric field lines.

It is just a three-minutes video. A very short video...

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Baluncore said:
That will depend on the length and the orientation of the conductive bar magnet. You could use the magnets as nails, or lie them on the surface as electrical equipotentials or field boundary conditions.
What's the result if we run a current through the bar magnets? Are the results different? What will the magnetic field lines look like?

wonderingchicken said:
What's the result if we run a current through the bar magnets?
A bar magnet is long in one dimension. How do you position the bar magnets?
Do you stand them on their ends, or lie them flat, pointing in which way?

Baluncore said:
A bar magnet is long in one dimension. How do you position the bar magnets?
Do you stand them on their ends, or lie them flat, pointing in which way?
Lets start by standing the bar magnets up vertically instead of laying them horizontally in the container.

I think it will look something like this...

if the poles that pointing to each other are similar.

and this...

if the poles are dissimilar.

Combine these magnetic field lines with a 3D electric field lines like the image below...

will result to field lines that consisted of intersecting and non-intersecting field lines.

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Baluncore said:
A 2D diagram cannot map both the perpendicular E and M fields at the same time.
If you convert one, then attempt to map both at the same time, the result will be neither, but the sum of the two.
That bolded statement, do you mean if we combined a 2d picture of magnetic field lines and 2d picture of electric field lines we'll never see the perpendicular E and M fields at the same time? What's the context here?

wonderingchicken said:
Lets start by standing the bar magnets up vertically instead of laying them horizontally in the container.
So the field lines go immediately down, then rise up through the paper before descending to the pole above. The electric field in the conductive paper remains in the plane, but is distorted to spiral in on the pole, by the slight magnetic deflection of the current, by the Lorentz force. The hand of the spiral will be determined by the polarity of the magnet, and the polarity of the electric potential.

wonderingchicken said:
That bolded statement, do you mean if we combined a 2d picture of magnetic field lines and 2d picture of electric field lines we'll never see the perpendicular E and M fields at the same time? What's the context here?
You are attempting to display in 2D, what is a combination of two 3D vector fields, which is impossible without loss of information.
You can refine the context by asking a better defined question.

Baluncore said:
So the field lines go immediately down, then rise up through the paper before descending to the pole above. The electric field in the conductive paper remains in the plane, but is distorted to spiral in on the pole, by the slight magnetic deflection of the current, by the Lorentz force. The hand of the spiral will be determined by the polarity of the magnet, and the polarity of the electric potential.

I don't have the right app for me right now to try to draw what you're describing, but are you saying the resulting line will be similar to what I said which is "field lines that consisted of intersecting and non-intersecting field lines"?

Baluncore said:
So the field lines go immediately down, then rise up through the paper before descending to the pole above. The electric field in the conductive paper remains in the plane, but is distorted to spiral in on the pole, by the slight magnetic deflection of the current, by the Lorentz force. The hand of the spiral will be determined by the polarity of the magnet, and the polarity of the electric potential.

So, magnetic field can somehow influence the electric field lines and vice versa?

wonderingchicken said:
... , but are you saying the resulting line will be similar to what I said which is "field lines that consisted of intersecting and non-intersecting field lines"?
How can field lines intersect other field lines of the same field?
What different fields are you considering.

wonderingchicken said:
So, magnetic field can somehow influence the electric field lines and vice versa?
https://en.wikipedia.org/wiki/Magnetohydrodynamics

Baluncore said:
How can field lines intersect other field lines of the same field?
What different fields are you considering.

So the directions of both E and B/H field lines are exactly the same? Is that what you're saying?

Baluncore said:

Thank you.

Baluncore said:
How can field lines intersect other field lines of the same field?
What different fields are you considering.

What I mean is what will the field lines (including the electric field lines that we saw earlier in the video) look like if we use two erect bar magnets as the conductors instead of the nails like in the video? Did they (both the electric field lines and magnetic field lines) look like this...

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Baluncore said:
How can field lines intersect other field lines of the same field?
What different fields are you considering.

I thought the resulting field lines will look like this...

The black line is the electric field lines that is also the same electric field lines that we saw in the video. Sorry for the terrible drawing of electric field lines.

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