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Electromagnetic Field

by DB
Tags: electromagnetic, field
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marlon
#19
Jan24-05, 04:34 PM
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Quote Quote by dextercioby
Marlon,i ain't gonna quote you on each reply...It's not magntostatics and neither electrostaics involved when discussing the "bond" between the electric field & the magnetic field...
Your mistake was insterting the 2 long words in the paragraph they should have never been in the first place.Plus the rather dubious:

What is basic electrstatics and magnetostatics...??

Daniel.

P.S.Damn,i quoted u again...
Sighs,...please, stop starting discussions based upon personal views...

marlon

ps : basic means elementary
dextercioby
#20
Jan24-05, 04:40 PM
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Is that a rather elegant way to end discussions in which u're wrong...??

Daniel.

P.S.Maybe i'll teach QM one day and i'll surely as hell won't use the word "orbital" as a substantive...
marlon
#21
Jan24-05, 04:50 PM
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Quote Quote by dextercioby
Is that a rather elegant way to end discussions in which u're wrong...??

Daniel.

P.S.Maybe i'll teach QM one day and i'll surely as hell won't use the word "orbital" as a substantive...

For the last time, i politely ask you what was my mistake ???

ps : you already know what orbital means ???

marlon
dextercioby
#22
Jan24-05, 04:59 PM
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Well,Marlon,no mean to offend,but you've had almost an hour to figure out that the your remark with "basic electrostatics and megnetostatics" was totally inappropriate in the context your previous phrase had created...

Daniel.
pervect
#23
Jan24-05, 11:28 PM
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If you put a charge up a parallel plate capacitor to a voltage V, the charge on each plate will be q = C*V, and the electric field will be V/d, where d is the distance between the plates. The direction of the field will be normal to the plates.

The magnetic field inside a charged capacitor will be zero.

If you place a magnet near a charged capacitor, the arrangement of charge on the capacitor will not be disturbed. The Lorentz force law shows that a magnetic field will affect only moving charges. The charges on the capacitor plates will be nonmoving when the capacitor is in equilibrium.

[add for clarity]
You may get some small disturbance of the electric field if the magnet is conductive, but this can be minimized. There's no intrinsic reason that the presence of a static magnetic field will affect a static electric field.

The presence of the electric field will not disturb the magnet either.

In short, there are six independent quantities, Ex, Ey, Ez, Bx, By, Bz that describe the electromagnetic field at any point in space. Each of them can be set independently of the other. If you set Ex and Bx to be nonzero, and the other four components to be zero, you have set up a situation where the electric and magnetic fields are not perpendicular.
dextercioby
#24
Jan25-05, 01:50 AM
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Okay,and to put it a form so that Marlon could finally understand what u were talking about..."That is basic electrostatics and magnetostatics"... The field equations are decoupled.U can do whatever u want with the fields,since they are independent of each other...

Daniel.
Gza
#25
Feb21-05, 06:31 PM
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i guess dexter wins that round!
krab
#26
Feb21-05, 09:29 PM
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Quote Quote by DB
Why is it that as a particle propagates through an electromagnetic field, the electric and magnetic forces are perpendicular to eachother?
Electric and magnetic forces need not be perpendicular at all. For example, magnetic and electric fields can be perpendicular to each other in such a way that the electric and magnetic forces are parallel. One can make them in opposite directions so that they cancel. Such a device is called a spin rotator, or Wien filter. It is in common use; I've designed some myself.
siddharth
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Feb22-05, 12:29 AM
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Quote Quote by pervect
If you place a magnet near a charged capacitor, the arrangement of charge on the capacitor will not be disturbed. The Lorentz force law shows that a magnetic field will affect only moving charges. The charges on the capacitor plates will be nonmoving when the capacitor is in equilibrium.
Now, if i place the magnet near the capicitor and then move with a constant velocity v, then the charges on the capicator will have a velocity relative to me. Therefore they should experience a force and are expected to accelerate and rearrange.
But there will also be Electric field in the new frame. My question is whether the existing electric field due to the charges in the capactior will change so as to produce no net force, or whether there will be an electric field due to the magnet also in the new frame.
pervect
#28
Feb25-05, 01:58 AM
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Quote Quote by siddharth
Now, if i place the magnet near the capicitor and then move with a constant velocity v, then the charges on the capicator will have a velocity relative to me. Therefore they should experience a force and are expected to accelerate and rearrange.
But there will also be Electric field in the new frame. My question is whether the existing electric field due to the charges in the capactior will change so as to produce no net force, or whether there will be an electric field due to the magnet also in the new frame.
I'm not quite sure who is moving in your example.

Assuming we have a magnet moving relative to a capacitor:

In the magnet frame, the charges experience the Lorentz force because they are moving through a magnetic field, and there is no electric field.

In the capacitor frame, the charges experience an electrostatic force due to the fact that a moving magnetic field transforms to an electric field.

However, because the charges are stationary in the capacitor frame, the Lorentz force due to the magnetic field is zero - force = v cross B, and v=0, so the force due to the magnetic field is zero.

So both observers agree that there is a force, one however attributes the force as being due to a magnetic field, and the other oberver interprets the force as being due to an electric field.


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