At What Speed Does a Magnet's Flux Field Travel?

[pinestone]

At what speed does a magnet's flux field travel

 

[Tide]

If it's traveling then it is electromagnetic meaning that it travels at c.

 

[pinestone]

How can it be "electro" ? It's just magnetic. Isn't magnetism a force, and not a wave? A wave occurs within a period of time. There is no reference frame for flux. A magnetic field is a continuous loop- A bi-directional and inter-dependent pair of forces.

"Question everything"...Albert Einstein

 

[ZapperZ]

How can it be "electro" ? It's just magnetic. Isn't magnetism a force, and not a wave? A wave occurs within a period of time. There is no reference frame for flux. A magnetic field is a continuous loop- A bi-directional and inter-dependent pair of forces.

Check the Maxwell equation. I can easily describe a magnetic field as a varying E-field. Furthermore, the speed of propagation of a magnetic field is no different than the speed of propagation of E field. Both of these are tied together at birth!

Zz.

 

[pinestone]

Well the flux capacitor requires a speed of 88 mph...wait a second, I think I misunderstood the question...

It has been suggested that magnetic lines of force (flux) travel (if, indeed they do) at the speed of light. This seems to be the current theory, anyway. And, what capacitor could slow light down to 88 mph?

 

[Cyrus]

So, if I am to understand this correctly, a person asked in a previous post about time delay in the measurement of an E field of a star moving away from an observer. In that case, an E field would be distinct at every instant in time. So let's say at time $$t_0 + \Delta t$$, the charged star has moved an incremental displacement away, $$v \Delta t$$. So the new E field being created at this instant would be based on the new $$\frac{1}{r^2}$$ relationship, $$\frac{1}{(r+v \Delta t)^2}$$. Assuming the E field is steady and constant at time $$t_0$$, it would take $$\frac{r +v \Delta t}{c}$$ seconds before the new value of the E field from time $$t_0 + \Delta t$$ reaches the observer. So I would see the E field associated at time $$t_0 + \Delta t$$, at a later time, $$t_0 + \Delta t + \frac{r + \Delta t}{c}$$? Is that correct? Probably not..

 

[pinestone]

Check the Maxwell equation. I can easily describe a magnetic field as a varying E-field. Furthermore, the speed of propagation of a magnetic field is no different than the speed of propagation of E field. Both of these are tied together at birth!

Zz.

Yes, and Maxwell's equation provides us with zero. So these "electro" magnetic lines of flux are somehow being propagated by electron motion from what source of EMF ?

 

[ZapperZ]

Yes, and Maxwell's equation provides us with zero. So these "electro" magnetic lines of flux are somehow being propagated by electron motion from what source of EMF ?

Er... come again? Maxwell equations provides us with zero? I don't understand what you mean here. And it is being propagated by electron motion? Can you please show me where you get this? Maybe I can understand it better looking at the equation being described here.

Look, when you have a magnetostatic condition, there is no "speed" of propagation. Nothing is changing, so you have no way of measuring the speed of anything of the field. The word "flux" should not be confused with the pedestrian usage of the word. A "flux" in this context is simply

$$\int{B.dA}$$

Zz.

 

[dextercioby]

In this context FLUX$\neq$ FLOW...

Daniel.

 

[AlphaNumeric]

And, what capacitor could slow light down to 88 mph?

If you missed the joke, he/she was referring to the films 'Back to the Future' where the time machine has a flux capacitor and the car has to reach 88mph before it would be able to travel in time.

 

[pinestone]

If you missed the joke, he/she was referring to the films 'Back to the Future' where the time machine has a flux capacitor and the car has to reach 88mph before it would be able to travel in time.

Yea, I got the joke. What is so funny about the word "flux"? This is a classical physics forum, isn't it? A flux capacitor belongs in QED, and not here. And just for reference, there really is a flux capacitor- try Google.

 

[pinestone]

...Look, when you have a magnetostatic condition, there is no "speed" of propagation. Nothing is changing, so you have no way of measuring the speed of anything of the field. The word "flux" should not be confused with the pedestrian usage of the word. A "flux" in this context is simply

$$\int{B.dA}$$

Zz.

You say that the "electro" magnetic lines of force (aka "flux") have no measurable motion. No speed. No movement. And, they are at rest. If so, which kind of "electron" has no motion?

 

[ZapperZ]

You say that the "electro" magnetic lines of force (aka "flux") have no measurable motion. No speed. No movement. And, they are at rest. If so, which kind of "electron" has no motion?

Is there a reason why you keep invoking electron motion? Why would "electron" be a part of this? Please show me a formulation of magnetic flux that explicitly involves "electron motion".

You are asking me to explain something that only you have seen or understood. I'm sure you realize what an impossible task this is. If you could cite a clear reference where you understood or read these things, it will be me a lot easier, since obviously, we are getting nowhere fast on this.

Start by defining a magnetic flux.

Zz.

 

[pinestone]

Is there a reason why you keep invoking electron motion? Why would "electron" be a part of this? Please show me a formulation of magnetic flux that explicitly involves "electron motion".

You are asking me to explain something that only you have seen or understood. I'm sure you realize what an impossible task this is. If you could cite a clear reference where you understood or read these things, it will be me a lot easier, since obviously, we are getting nowhere fast on this.

Start by defining a magnetic flux.

Zz.

Yes, OK- I'll reply to you soon...:shy:

 

[skywolf]

you don't detect a wave until the entire wave has passed your sensor right? in that case, wouldn't you detect the speed of flux to be slightly lower than c?

 

[ZapperZ]

you don't detect a wave until the entire wave has passed your sensor right? in that case, wouldn't you detect the speed of flux to be slightly lower than c?

So you see the sun during night time then?

Zz.

 

[Tide]

you don't detect a wave until the entire wave has passed your sensor right? in that case, wouldn't you detect the speed of flux to be slightly lower than c?

Not exactly. By your argument you would also have to take into account the same lag required for the "entire" wave to have been emitted.

 

[pinestone]

...Is there a reason why you keep invoking electron motion?...
Zz.

As I understand it, a magnetic field is an entity produced by moving electric charges which exerts force on other moving charges. These electric charges are a characteristic of subatomic particles. One of these particles being an electron. Did I miss something here?

 

[ZapperZ]

As I understand it, a magnetic field is an entity produced by moving electric charges which exerts force on other moving charges. These electric charges are a characteristic of subatomic particles. One of these particles being an electron. Did I miss something here?

Yeah, but the moving charges that produces the magnetic field does NOT travel with the field! It is the source, but you were asking about the magnetic flux. I asked you to look at the definition of a magnetic flux. You will see that the source doesn't "flow" into the area that is being measured for the flux.

Besides, moving charges is CURRENT, not a magnetic flux.

So tell me what exactly do you want?

Zz.

 

[pinestone]

... definition of a magnetic flux. You will see that the source doesn't "flow" into the area that is being measured for the flux.

Besides, moving charges is CURRENT, not a magnetic flux.

So tell me what exactly do you want?

Zz.

For a measured quantity of magnetism, is it moving? And if it is, at what speed?

 

[ZapperZ]

For a measured quantity of magnetism, is it moving? And if it is, at what speed?

By definition, a magnetostatic condition does not have any "moving" magnetic field intensity.

So now it is YOUR turn to tell me something. What is a "magnetic flux"? Keep in mind that this phrase has a SPECIFIC definition in physics, and you're in a physics forum.

Zz.

 

[pinestone]

...What is a "magnetic flux"? ...Zz.[/QUOTE To quote from Maxwell: "In the case of fluxes, we have to take the integral, over a surface, of the flux through every element of the surface. The result of this operation is called the surface integral of the flux. It represents the quantity which passes through the surface."

 

[ZapperZ]

"The strength and the extent of a magnetic field". Right?

Nope.

I have already defined it. The magnetic flux is defined as

$$\Phi = \int{\vec{B} \cdot d\vec{A}}$$

This means that it is the sum over a surface of the perpendicular component of the B field across that surface. The B field could be a constant in time, meaning nothing is "flowing" under a magnetostatic condition.

This definition is similar to the electric flux. If you have done Gauss's Law, it is the same thing. Again, nothing is "moving" here if you have a static condition.

Zz.

 

[pinestone]

Nope.

I have already defined it. The magnetic flux is defined as

$$\Phi = \int{\vec{B} \cdot d\vec{A}}$$

This means that it is the sum over a surface of the perpendicular component of the B field across that surface. The B field could be a constant in time, meaning nothing is "flowing" under a magnetostatic condition.

This definition is similar to the electric flux. If you have done Gauss's Law, it is the same thing. Again, nothing is "moving" here if you have a static condition.

Zz.

Sorry about the late edit, but I'm on a very slow dialup connection in the middle of the woods. Thank you for the excellent explanation. However, what started all this was Maxwell, and his "...It represents the quantity which passes through the surface." I wondered, if it is passing through, then at what speed is it doing so?

 

[ZapperZ]

Sorry about the late edit, but I'm on a very slow dialup connection in the middle of the woods. Thank you for the excellent explanation. However, what started all this was Maxwell, and his "...It represents the quantity which passes through the surface." I wondered, if it is passing through, then at what speed is it doing so?

This is simply a representation of magnetic fields as LINES. There is nothing moving here in a static situation.

Draw several parallel lines. Now draw a line perpendicular and across to those lines, somewhere in the middle of the parallel lines. What you have is a bunch of parallel lines crossing or passing through that line. But you can't say those parallel lines are "moving" across at some speed, can you?

That's the same thing with flux in this case. It is simply a SUM of all the magnetic fields that crosses a particular area. Nothing needs to move.

Zz.

 

[pinestone]

Yes, I see. Thank you.