# Can magnet fields deflect displacement currents?

## Main Question or Discussion Point

Can magnet fields deflect displacement currents?

Could displacement currents be made to propagate in spirals like those in a cyclotron?

Do they travel close to the speed of light?

Can they be focused into beams?

Can they transmit electrical energy at a distance?

Are they subject to the same friction as electrons?

Can they be used to charge capacitors from outside a circuit?

Are there any significant applications of displacement current at present? If not, then why is that?

Related Classical Physics News on Phys.org
The displacement current has units of current but there is no physical charge present.

Magnetic fields do not exert forces on one another or magnetics would be a nonlinear phenomenon.

In short, magnetic fields exert forces on moving charges, not on other magnetic fields.

Magnetic fields do not exert forces on one another or magnetics would be a nonlinear phenomenon.

In short, magnetic fields exert forces on moving charges, not on other magnetic fields.
really.......

Magnetic fields do not exert forces on one another or magnetics would be a nonlinear phenomenon.
Are you saying that the concept of nonlinear magnetic phenomenon is outside of science? Just in what sense do you mean by "nonlinear phenomenon"?

In short, magnetic fields exert forces on moving charges, not on other magnetic fields.
Are you saying that magnetic fields can only interact with an electric field if the divergence of the electric field is non-zero?

Are you suggesting that there is type of changing electric field that the magnetic field cannot interact with?

Why say this when whether or not something is purely electric, purely magnetic, or somewhere in between depends on the reference frame of the observer?

Last edited:
Meir Achuz
Homework Helper
Gold Member
"Can magnet fields deflect displacement currents?"
Yes. If a magnetic field passed between the plates of a charging capacitor.
the EM momentum given by DXB would change. This would be balanced by a torque on the capacitor. The torque would be the same as for a current I=dD/dt.
(I have left out extraneous factors.)

"Can magnet fields deflect displacement currents?"
Yes. If a magnetic field passed between the plates of a charging capacitor.
the EM momentum given by DXB would change. This would be balanced by a torque on the capacitor. The torque would be the same as for a current I=dD/dt.
(I have left out extraneous factors.)
Clem, this is not correct. The displacement currents do create magnetic fields. But they cannot be deflected by magnetic fields because they are not moving charges.

If they could then you could deflect a beam of light with a magnet. But you can't.

Clem, this is not correct. The displacement currents do create magnetic fields. But they cannot be deflected by magnetic fields because they are not moving charges.

If they could then you could deflect a beam of light with a magnet. But you can't.
But light doesn't have a net displacement current. I mean, it alternates between positive and negative, does it not? So that's not something that would be easy to observe, right?

But guess what, it turns out there are several effects out there where light can interact with magnetic fields. See:

http://en.wikipedia.org/wiki/Magneto-optic_effect

Can a strong magnetic field warp light?
so i know that gravity and a magnetic field is different but i was wondering if maybe a strong magnetic field can create gravity.
the question is can you align magnets in such a way that it would cause their to be a strong point of which the magnetic pull is stronger due to the alignment. kind of like magnifying the strength into a center point? also can you use such a device to pull on light rays?
or can you make a strong enough electromagnet to serve the same purpose (pull on light)?
if either is possible then could you not use such a device to pull or warp light around an object to make it invisible to the eye?

haha yea i know it's a pretty large question
Yes,

magnetic fields have several effects upon electromagnetic waves (such as light).

Here are a few:
Zeeman effect
Magneto Optical Kerr effect

The one you are probably most interested in is:

In principle you may be able to use magnetic fields to deflect light around an object, but in practice the fields would be huge. Too large to be practical.

Here is a summary of some of the effects:
http://en.wikipedia.org/wiki/Magneto-optic_effect
Morningfox said:
Basically, no. A magnetic field doesn't create gravity, and can't warp light.

But ... there is an exception for very strong magnetic fields, which can do a *very* tiny bit of warping.

Maxwell's equations are linear and there is therefore no interaction between magnetic fields. The magnetic field of the dipole magnet satisfies the Maxwell equations. The electromagnetic waves from your laser is another solution. Add them up and the sum of the two solutions is another solution.

So, this suggests that there shouldn't be a deflection. This is not 100% true. The most important effect that does lead to a deflection is the fact that the magnet induces changes in the air that the laser light moves through. Even though the full problem is linear, if you pretend that the medium isn't there, then it is effectively nonlinear.

But even in a perfect vacuum there are Quantum Electrodynamics (QED) effects due to virtual electron positron pairs. The magnet effectively changes the QED vacuum and then the laser light that moves through it will be deflected. When light enters a region with a magnetic field, then it behaves as if there is an index of refraction. This effect is largest if the light enters the region orthogonal to the magnetic field. The two polarizations states of the light with the magnetic component parallel or orthogonal to the external field have different indices of refraction. That causes the so-called vacuum birefringence effect.
Source(s):
http://arxiv.org/abs/hep-ph/9806417