Do Magnetic Fields Exist in All 3 Cases?

[goodname]

Do magnetic field is produced in all the following 3 cases?

Case 1: An isolated electron moving linearly with constant velocity in space.

Case 2: An electron moving inside a copper conductor linearly(current).

case 3: A ball( made up of many molecules, in-turn atoms, in-turn electrons but firmly hold by parent atom in its orbit-insulator) moving linearly with constant velocity in ground.

 

[sophiecentaur]

I think Yes for 1 and 2 but No for 3 because there is no net charge (?) on the ball.

 

[Drakkith]

Hrmm. I think in case number 3 the answer is maybe. There wouldn't be one from the motion of the ball as a whole, but maybe if the material was a magnetic material with its atoms and molecules aligned correctly to produce a magnetic field.

 

[sophiecentaur]

Yes but, once you start on what-ifs there's no end to it and OPs can get more and more confused when the simple answer gets buried.

 

[{~}]

Is that how the question is exactly worded? I think this is one those questions that tries to get you to discover something by thinking about it but from the way its worded I'm just not sure.

 

[goodname]

Do magnetic field is produced in all the following 3 cases?

Case 1: An isolated electron moving linearly with constant velocity in space.

Case 2: An electron moving inside a copper conductor linearly(current).

case 3: A ball( made up of many molecules, in-turn atoms, in-turn electrons but firmly hold by parent atom in its orbit-insulator) moving linearly with constant velocity in ground.

Thanks for all your replies. My Mothertongue is not English. Let me reframe the question more clearly.

Charge is the property of an electron which is unique and constant in all position and all time. That is charge of the electron is same whether it is in a ball or in a copper conductor or in a vacuum as isolated unit.

Motion of any matter represents that the position of the matter changed in space over time.
For exmaple, an electron is said to have undergone motion if the position of the electron in time T1 is ( 5,4,3) using 3 dimensional cartesian co ordinates and is (9,8,4) at another time T2.


That is the electron undergoes motion whether it is the isolated electron in free space by some mysterious unknown force or driven by electrical imbalance in copper conductor or a ball mechanically hit by a bat.

Magnetic field is generated in case 2, there is experimental evidence- electromagnets and CRT.

Case 1 and 3 have similarities, that is the electric field of the electron which is under discussion is not disturbed before, during and after the motion. The motion is not driven by electrical imbalance but by other non electrical forces.

So the questions are, Do the creation of magnetic field by the electron needs motion? and should the motion must be created by electrical forces alone? Do the motion created by mechanical and gravitational forces on electron produce magnetic field?

 

[sophiecentaur]

Haven't you ignored that equal number of positive charges on the ball - cancelling out the 'moving charge' effect?

 

[goodname]

Haven't you ignored that equal number of positive charges on the ball - cancelling out the 'moving charge' effect?

To sophiecentaur,
The effect of the charge at a point in space is indicated by its Electric field intensity at the point, which is defined as the force experienced by the unit positive charge at that point. so consider an electron at (0,0,1). The effect of the charge of the electron at any point in space is nullified or canceled if and only if another particle with equal charge but positive located at the same location. That is 1c and -1c charge located at same position in space, that is impossible because electron is a matter.

Practically the electron and positive charge located apart say electron at (0,0,1) and positive charge at (0,0,2) The Electric field intensity actually increases between the co ordinates (0,0,1) and (0,0,2) but decrease and tends to zero outside these co ordinates. The ball is neutral(though not 100 percent) in a hand of a person but net charge around the vicinity of electron is present and finite. So it is still "moving charge" when a ball hit by a bat.

 

[sophiecentaur]

OK, but the model is getting more and more complicated as we go on. Of course, any (as yet unspecified) unbalanced / net charge will change the situation entirely.

 

[Doc Al]

So the questions are, Do the creation of magnetic field by the electron needs motion?

Yes.

and should the motion must be created by electrical forces alone?

No.

Do the motion created by mechanical and gravitational forces on electron produce magnetic field?

Yes. (Though I suspect that any mechanical--contact--force will prove to be electrical.)

 

[goodname]

Yes.

No.

Yes. (Though I suspect that any mechanical--contact--force will prove to be electrical.)

An isolated electron(with net charge) moving relative to a stationary non electrical object( zero net charge) and the non electrical object(zero net charge) moving relative to stationary electron are indistinguishable under relative motion. Will the stationary electron produce magnetic field when the non electrical object is in motion?

 

[Doc Al]

An isolated electron(with net charge) moving relative to a stationary non electrical object( zero net charge) and the non electrical object(zero net charge) moving relative to stationary electron are indistinguishable under relative motion.

That's right. One could view the physics from either frame, each equally valid.

Will the stationary electron produce magnetic field when the non electrical object is in motion?

No, but electric and magnetic fields are frame-dependent concepts. What looks like an electric force in one frame, will look like a magnetic force in another.

 

[goodname]

Thanks. So charge(electron) is the one and only source of magnetic filed and it produces magnetic field only when it is motion/relative motion. How does an electron know/sense/realize itself that it is in motion/relative motion and will be able to produce magnetic filed proportional to the velocity of the motion? What is the need/objective(?) to produce magnetic field only when it is in motion? Is there any explanation/mechanism beyond this?

 

[Drakkith]

Thanks. So charge(electron) is the one and only source of magnetic filed and it produces magnetic field only when it is motion/relative motion. How does an electron know/sense/realize itself that it is in motion/relative motion and will be able to produce magnetic filed proportional to the velocity of the motion? What is the need/objective(?) to produce magnetic field only when it is in motion? Is there any explanation/mechanism beyond this?

Electrons don't know anything, they are not capable of thought. It is merely a property of how everything works. A magnetic field is a consequence of relativity and electric forces, hence why depending on the frame you are in it can look like an electric field or a magnetic field.

Also, I'm not sure why you are discounting Protons from your posts. They have a positive charge and have spin and such. As they move around they will be creating magnetic fields as well. A neutral baseball is producing equal amounts of positive and negative electric forces. So I would think that it is also producing the same but opposite magnetic fields, canceling out any net effect. (I would think. I'm not 100% sure on that.)

 

[goodname]

Electrons don't know anything, they are not capable of thought. It is merely a property of how everything works. A magnetic field is a consequence of relativity and electric forces, hence why depending on the frame you are in it can look like an electric field or a magnetic field.

Also, I'm not sure why you are discounting Protons from your posts. They have a positive charge and have spin and such. As they move around they will be creating magnetic fields as well. A neutral baseball is producing equal amounts of positive and negative electric forces. So I would think that it is also producing the same but opposite magnetic fields, canceling out any net effect. (I would think. I'm not 100% sure on that.)

To Drakkith,

consider someone is carrying an electron in his one hand and a magnetic compass in another hand, both are nearer to each other and he is traveling in a truck moving at 100 mph.

If the statement "Electron in motion produce magnetic field" is true, then for the person who is traveling in the truck notes there is no motion and so no magnetic filed produced by electron and the magnetic compass in his other hand should not show any deflection.

For a person who is standing in the road and watching the arrangement, the electron is in motion and should produce magnetic field and the magnetic compass should show deflection.

Consider 2 frames of reference, anyone can be possible but not both. Any explanation?

 

[Doc Al]

consider someone is carrying an electron in his one hand and a magnetic compass in another hand, both are nearer to each other and he is traveling in a truck moving at 100 mph.

If the statement "Electron in motion produce magnetic field" is true, then for the person who is traveling in the truck notes there is no motion and so no magnetic filed produced by electron and the magnetic compass in his other hand should not show any deflection.

For a person who is standing in the road and watching the arrangement, the electron is in motion and should produce magnetic field and the magnetic compass should show deflection.

Consider 2 frames of reference, anyone can be possible but not both. Any explanation?

Things are more complex than that. While I haven't analyzed this particular example in detail, rest assured that all frames will see the same effect. Realize that in the frame in which the electron and magnetic compass are moving, there is an electric field induced in the compass needle. The net effect is that the electric force cancels out the magnetic force. All frames see the same thing: The compass needle randomly oriented about the electron, unaffected by its presence.

 

[sophiecentaur]

The "electron in motion" is in motion Relative To the observer if it is to produce (the effect of) a Magnetic Field. You surely don't believe that fields are 'Actually There', do you? They are just one way of describing what happens. Just like the rest of Science, when you get down to it.

An observer who is looking at the electron and the compass go past at the same speed will see the Compass needle not being affected (because it isn't). You can't change the value of the angle of a compass needle just by traveling relative to it.

 

[goodname]

Things are more complex than that. While I haven't analyzed this particular example in detail, rest assured that all frames will see the same effect. Realize that in the frame in which the electron and magnetic compass are moving, there is an electric field induced in the compass needle. The net effect is that the electric force cancels out the magnetic force. All frames see the same thing: The compass needle randomly oriented about the electron, unaffected by its presence.

To Doc Al;
What would happen if the magnetic compass is replaced by a iron needle. iron needle will not produce any fields whether in rest or motion. So what would it seem for the observer in truck and observer in road. Will the iron needle shows any deflection/attraction to anyone of the observers?

 

[Doc Al]

To Doc Al;
What would happen if the magnetic compass is replaced by a iron needle. iron needle will not produce any fields whether in rest or motion. So what would it seem for the observer in truck and observer in road. Will the iron needle shows any deflection/attraction to anyone of the observers?

The electric field of the electron will induce a polarization charge in the iron needle, creating an attractive force between them. Again, the two sets of observers will see the same effect.

 

[goodname]

The electric field of the electron will induce a polarization charge in the iron needle, creating an attractive force between them. Again, the two sets of observers will see the same effect.

Okay. How it could be? Both the observers cannot see the same effect? The observer in the truck should see the force due to the effect of polarization. The observer in the road should see the effect of magnetic attraction force plus the force due to the effect of polarization..Is it correct?

 

[sophiecentaur]

Why shouldn't they see the same effect? If a datalogger were on board the experiment and sent the value of the compass angle by wireless, the data couldn't possible be changed during transmission, could it? think you are looking for some sort of paradox here and there isn't one.
The (what we call) stationary observer would see the compass (or iron needle) moving and would / could detect a magnetic or electric force as it went past. He would also detect an electric / magnetic effect from the passing electron. He could do the sums with these measurements and could predict exactly how the electron is affecting the compass. He would actually see this happening to the compass.

 

[goodname]

Why shouldn't they see the same effect? If a datalogger were on board the experiment and sent the value of the compass angle by wireless, the data couldn't possible be changed during transmission, could it? think you are looking for some sort of paradox here and there isn't one.
The (what we call) stationary observer would see the compass (or iron needle) moving and would / could detect a magnetic or electric force as it went past. He would also detect an electric / magnetic effect from the passing electron. He could do the sums with these measurements and could predict exactly how the electron is affecting the compass. He would actually see this happening to the compass.

I am not looking for any paradox. What I am thinking is, the statement "moving electrons produce magnetic field" is not completely true.

May be "Magnetic fields are produced by electron(and proton or other particles whatever that has property of charge) one and only when they are set in motion by disturbing their electric field.

All other types of motion facilitated by mechanical forces, gravitational forces,( or anything which do not disturb the electric field around the electron) cannot produce magnetic filed as in the case of person carrying electron in hand while traveling in a truck.

If the above statement is incorrect, Is there any experimental evidences available for production of magnetic field by electrons in motion which is not created by electrical field disturbance?

There are many experimental evidences for electron motion by electric field like current in a copper wire which can attract iron fillings by its magnetic force and cathode ray tube,etc...

 

[sophiecentaur]

I don't see why an electron which is moving due to one cause should be different from an electron moving by any other cause. Electrons in a CRT behave the same as electrons in a wire and in a Hall Effect device. In all three cases, a magnetic field will interact with them so, by inference, they can be regarded as producing their own magnetic field. BUT, as we know, the Field is only a thing in our heads, which explains a phenomenon. I could ask you how you would get an electron moving, separated from any neutralising positive charges, with anything other than an electric field? A nearby mass would attract particles with both signs of charge alike.

 

[goodname]

..many good explanations...anyway it seems to be a 'heavily' abstract topic. "Fields are thing in our mind" but it exists, it does not have mass, shape, energy but influence of charged particles...

 

[sophiecentaur]

Fields do not "exist" except in as far as they explain an effect. A field is a model that describes how the force on an object varies in space.
For instance, when two charges are brought together, we can explain the effect by saying that one charge has a field around it and the other charge is affected by that field. We say one has a field but the other is just a charge. Which one do we choose? It doesn't matter because we only introduce the idea of a field as a trick to work out the force. We don't need to 'believe' it's really there.

 

[Antiphon]

Actually much of this thread has it wrong.

Electrons produce no magnetic fields (except the moment due to spin). Magnetic fields are the result of time-changing electric fields, and there does not even need to be a charge nearby as in the case of a planewave.

Edit: Most of the posters in the thread know this; I mean much of the confusion surrounding the original question is due to thinking that electric and magnetic fields are separate from one another as DocAl pointed out.

Charges really only create electric fields. Magnetic charges, those would create magnetic fields if there were such objects.

 

[sophiecentaur]

You are saying that a beam of electrons in a CRT have No associated magnetic field when the current in the wire to the Cathode Has a field? That is hard to accept/

 

[goodname]

You are saying that a beam of electrons in a CRT have No associated magnetic field when the current in the wire to the Cathode Has a field? That is hard to accept/

I think no one in this thread said that "beam of electrons in a CRT have No associated magnetic field". Electron beam in the CRT is deflected by magnetic coils systems. So magnetic field is definitely associated there.

 

[goodname]

Actually much of this thread has it wrong.

Electrons produce no magnetic fields (except the moment due to spin). Magnetic fields are the result of time-changing electric fields, and there does not even need to be a charge nearby as in the case of a planewave.

Edit: Most of the posters in the thread know this; I mean much of the confusion surrounding the original question is due to thinking that electric and magnetic fields are separate from one another as DocAl pointed out.

Charges really only create electric fields. Magnetic charges, those would create magnetic fields if there were such objects.

Of-course Magnetic fields are the result of time-changing electric fields but Electric Field could not be a separate thing from electron. It is a massless component of electron(or other charge carriers).
Plane waves have magnetic field component at a point at a time because there is disturbance of electric field( in-turn the position of source electron) at a different place and at a different time.

And why this disturbance travel at a particular velocity 3*10^8 m/s?

 

[Antiphon]

You are saying that a beam of electrons in a CRT have No associated magnetic field when the current in the wire to the Cathode Has a field? That is hard to accept/

No, clearly they do. But what's really happening is the electrons create an electric field. We then see it as a combination of electric and magnetic fields because they are not in our reference frame.

 

[Crazymechanic]

in the CRT the magnetic deflection which is used to guide the electron beam is only useful because the electrons are in motion so here we go again , charged particles moving create magnetic fields which can interact with the charged particles that are moving into the wire of the deflection coil and hence the outcome.

even though the more fundamental would be the electric field if we want to get down to the " chicken or egg" debate.
As logically it follows that electric field + motion or increase decrease in field strength = magnetic field.