Exploring the Electric Field of a Moving Charge

[Rev. Cheeseman]

How does an electric field of a moving charge, for example a moving electron, inside a wire looks like? Does it looks like this with distorted circular radial lines?

 

[Dale]

I would again recommend that you get some computer algebra software and program this yourself. Then you would know it is right.

That said, this is not the field of an electron in a wire. It is roughly the field of a classical charge undergoing a brief acceleration in free space.

 

[Rev. Cheeseman]

I would again recommend that you get some computer algebra software and program this yourself. Then you would know it is right.

That said, this is not the field of an electron in a wire. It is the field of a classical charge undergoing a brief acceleration in free space.

I don't know how to programmed it myself as I'm just a person who are interested in physics with very limited mathematics background.

I tried to find pictures online on how an electric field of a moving charge inside a wire looks like, but there are just too many and I'm confused. What is the real difference between the electric field and the magnetic field of a, say, radio wave? Is electric field of a radio wave just a magnetic field viewed from different perspectives?

 

[Dale]

I don't know how to programmed it myself

We can help with that too. And then at the end you will have actually learned EM and programming

What is the real difference between the electric field and the magnetic field of a, say, radio wave?

There isn’t “really” a separate magnetic and electric field. They are different components of the electromagnetic field. The “real” thing is the combined electromagnetic field.

I tried to find pictures online on how an electric field of a moving charge inside a wire looks like

Inside a wire it doesn’t make too much sense to think about the field of an individual charge. They behave collectively. Their collective field simply points along the wire proportional to the current density.

 

[Rev. Cheeseman]

Their collective field simply points along the wire proportional to the current density.

Like this?

 

[Dale]

No, that is exactly what I said doesn’t make too much sense.

That figure is for people who already understand electromagnetism and are trying to use it to learn relativity. I don’t think “Purcell Simplified” will help you.

 

[Rev. Cheeseman]

No, that is exactly what I said doesn’t make too much sense.

That figure is for people who already understand electromagnetism and are trying to use it to learn relativity. I don’t think it will help you.

Can you think of any links that show the closest representations of what electric fields of every charges, not just individually but instead as the whole, actually look like?

 

[Dale]

Can you think of any links that show the closest representations of what electric fields of every charges, not just individually but instead as the whole, actually look like?

In what situation?

 

[Rev. Cheeseman]

In what situation?

For example, in current-carrying wires.

 

[Baluncore]

How does an electric field of a moving charge, for example a moving electron, inside a wire looks like?

How would you know which was your selected electron, there are so many other free electrons, going every which way, while drifting slowly along together as a current.

 

[Rev. Cheeseman]

How would you know which was your selected electron, there are so many other free electrons, going every which way, while drifting slowly along together as a current.

Can you think of any links that show the closest representations of what electric fields of every charges, not just individually but instead as the whole, actually look like?

 

[Baluncore]

Can you think of any links that show the closest representations of what electric fields of every charges, not just individually but instead as the whole, actually look like?

The electric field of the electrons on the wire can only be seen relative to the return circuit wire, which is at a different voltage and so establishes an electric field between the two wires. You need to know the geometry of the wires.
The equal and opposite current in the two wires, will sum to generate a magnetic field.

Top right;
https://en.wikipedia.org/wiki/Electric_dipole_moment#/media/File:VFPt_dipoles_electric.svg

 

[Rev. Cheeseman]

The electric field of the electrons on the wire can only be seen relative to the return circuit wire, which is at a different voltage and so establishes an electric field between the two wires. You need to know the geometry of the wires.
The equal and opposite current in the two wires, will sum to generate a magnetic field.

Top right;
https://en.wikipedia.org/wiki/Electric_dipole_moment#/media/File:VFPt_dipoles_electric.svg

In a single wire excluding second and other wires, the electric field will look like this?

https://en.wikipedia.org/wiki/Electric_charge#/media/File:VFPt_plus_thumb.svg
https://en.wikipedia.org/wiki/Electric_charge#/media/File:VFPt_minus_thumb.svg

 

[Rev. Cheeseman]

Top right;
https://en.wikipedia.org/wiki/Electric_dipole_moment#/media/File:VFPt_dipoles_electric.svg

So, for this wire in this particular video, the electric fields coming out from this wire excluding the other wires will look like the picture in your link?

 

[Baluncore]

... the electric fields coming out from this wire excluding the other wires ...

The electric field is radial, falling towards zero volts at an infinite distance, but that is impossible with a current carrying circuit because there must be a return conductor for current to flow. Notice the magnetic field is orthogonal to the electric field.

 

[Rev. Cheeseman]

The electric field is radial, falling towards zero volts at an infinite distance, but that is impossible with a current carrying circuit because there must be a return conductor for current to flow.

Therefore, the electric field for that current carrying wire will be like this.

Notice the magnetic field is orthogonal to the electric field.

Is there a way to make the electric fields and magnetic fields to be non-perpendicular, for example parallel? Looks like someone can make how the electric and magnetic fields propagate depending on how someone designed the source. I saw some articles about cavity resonators generating parallel electric and magnetic fields few days ago so I think that's possible. I'll try to find the article later.

 

[Baluncore]

I saw some articles about cavity resonators generating parallel electric and magnetic fields few days ago so I think that's possible.

Yes, but it is not useful, and it attenuates rapidly to make EM waves propagating as orthogonal E and M fields.

The cross product of E and M is the Poynting vector, the direction of energy flow, which is orthogonal to E and M, so is into or out of the paper, parallel to the current.

 

[Rev. Cheeseman]

Yes, but it is not useful, and it attenuates rapidly to make EM waves propagating as orthogonal E and M fields.

The cross product of E and M is the Poynting vector, the direction of energy flow, which is orthogonal to E and M, so is into or out of the paper, parallel to the current.

I guessed you've read the article, may I ask what is the title of the article? I forgot the title.

 

[vanhees71]

No, that is exactly what I said doesn’t make too much sense.

That figure is for people who already understand electromagnetism and are trying to use it to learn relativity. I don’t think “Purcell Simplified” will help you.

I don't think Purcell will help you at all, because the wire is treated not correctly there. The correct treatment is here:

https://itp.uni-frankfurt.de/~hees/pf-faq/relativistic-dc.pdf

 

[Baluncore]

I guessed you've read the article, may I ask what is the title of the article?

What article? What media? What about?

 

[Rev. Cheeseman]

What article? What media? What about?

The article in which you said "Yes, but it is not useful, and it attenuates rapidly to make EM waves propagating as orthogonal E and M fields."

 

[Baluncore]

The article in which you said "Yes, but it is not useful, and it attenuates rapidly to make EM waves propagating as orthogonal E and M fields."

I do not recall such an article.

 

[Rev. Cheeseman]

I do not recall such an article.

So, how do you arrive at the conclusion?

 

[Baluncore]

So, how do you arrive at the conclusion?

Which conclusion exactly?
I have been working in the world of EM and instrumentation for more than 40 years. I guess I might have picked a few things up along the way.

 

[Rev. Cheeseman]

Which conclusion exactly?

Here, "Yes, but it is not useful, and it attenuates rapidly to make EM waves propagating as orthogonal E and M
fields."

I have been working in the world of EM and instrumentation for more than 40 years. I guess I might have picked a few things up along the way.

Ok?

 

[Dale]

For example, in current-carrying wires.

Yes, I have a very good reference for that. But first, why are you looking for these diagrams? Do you just want pretty pictures to decorate your wall, or are you hoping to accomplish something?

 

[Rev. Cheeseman]

But first, why are you looking for these diagrams? Do you just want pretty pictures to decorate your wall, or are you hoping to accomplish something?

As decorations to show the varieties of forms of electric/magnetic fields.

 

[Rev. Cheeseman]

Which conclusion exactly?
I have been working in the world of EM and instrumentation for more than 40 years. I guess I might have picked a few things up along the way.

Are those electric/magnetic field combinations orthogonal? I think it depends on how someone look or think about them.

https://en.wikipedia.org/wiki/Class.../media/File:Lorentz_boost_electric_charge.svg

 

[Dale]

As decorations to show the varieties of forms of electric/magnetic fields.

Then it doesn’t really matter. Search the internet for the pictures you like the best. We are here for educational purposes, not decorating purposes.

Thread temporarily closed for mentor discussion

 

[berkeman]

After a Mentor discussion, this thread will remain closed.