magnets

[richardings]

what is the energy of a photon coming out of a standard everyday bar magnet?

what end of the electromagnetic spectrum will it be in?

[swansont]

The photons involved in the interaction are virtual. You only "detect" them if the interaction is occurring.

[lesolee]

what is the energy of a photon coming out of a standard everyday bar magnet?

what end of the electromagnetic spectrum will it be in?

 

If a (permanent) bar magnet were continuously emitting photons it would be an energy source and would "run down" (be depleted) over time.

Of course radioactive materials like glow-in-the-dark paint mixtures do run down eventually but that is a different mechanism.

 

It would be an interesting question to ask what the frequency or wavelength of the virtual photons mentioned by swansont are. That is somewhat above my level.

At my level there is simply a magnetic field storing the energy statically, not dynamically. I imagine the "virtual photons" are not able to be observed and have been postulated to exist to suit a theory.

[Enthalpy]

The frequency is zero, and the virtual photons are the field, whose force you feel when holding two magnets.

[lesolee]

The frequency is zero, and the virtual photons are the field, whose force you feel when holding two magnets.

 

Given E=h.f

a zero frequency photon should have no energy

This is clearly a difficult area.

[Enthalpy]

E=h*F is for a photon of positive energy and real wave number.

 

Nothing difficult. It's just that once you've said "virtual photon" you've made an analogy with other particles, but it brings little more.

[lesolee]

E=h*F is for a photon of positive energy and real wave number.

 

Nothing difficult. It's just that once you've said "virtual photon" you've made an analogy with other particles, but it brings little more.

 

There is a fuller explanation here ...

 

http://van.physics.i...ting.php?id=414

[richardings]

i assume if you can detect the photons, they are real.

 

so am I right in thinking the magnet will radiate 'virtual' photons until the photons need to interact with something, in which case the magnet will emit 'real photons'? or will the 'virtual' photons turn into 'real' ones? i guess the 'virtual' ones wont turn into 'real' ones as this may provide faster than light information travel.

 

given nothing interacting with a magnet, will it never lose its magnetism? i thought it would as energy has been put into the magnet to align the particles to make them magnetic in the first place, and over time these will revert back to random alignments and thus the field will diminish, sort of like radioactive decay.

 

 

if a magnet is in a universe with nothing in it (nothing for the magnet to interact with) will the magnet sustain its magnetism forever? constantly emitting 'virtual' photons?

 

am i right in saying that light involves 'real' photons and the electromagnetic force involves 'virtual' photons?

 

when are 'real' and 'virtual' photons used?

 

of course i kow this is related to quantum theory so will probably be a strange and hard to describe answer.

 

thanks

[lesolee]

given nothing interacting with a magnet, will it never lose its magnetism? i thought it would as energy has been put into the magnet to align the particles to make them magnetic in the first place, and over time these will revert back to random alignments and thus the field will diminish, sort of like radioactive decay.

 

Old designs of magnets certainly did lose their magnetic properties over time. There was (and still is) something called a "keeper" to maintain the strength of the magnet. You don't "use up" the magnet by letting the magnetic flux increase, in fact the opposite is the case.

 

http://www.coolmagnetman.com/magtypes.htm

 

As for all the vitual photon interactions, that's all way beyond a humble electronics designer.

[Anders Hoveland]

No, actually a permanent magnet does give off real photons. They are extremely long wavelength, and it is dependant on the movement of the magnet. If you moved a bar magnet yesterday, and plan to move it back to its original position tomorrow, it is currently in the process of emitting real photons, at least theoretically. Normally these photons will almost entirely be "virtual", it is only when there is an actual interaction with the magnetic field that they will become "real".

 

It may be difficult to conceptualise, but these photons are fundamentally no different than any other photons.