Isn't it a paradox ?

[Eldad Eshel]

There is something I can't seem to understand. On one hand light is an electromagnetic wave, as in made up of electric and magnetic fields moving through space. On the second hand it is said to create the electric field, by quantum electrodynamics. Don't these 2 heavily contradict each other ?

[swansont]

"It is said" by whom?

[Eldad Eshel]

"It is said" by whom?

That is what I understood about quantum electrodynamics. If I am wrong then what does it really say ?

[studiot]

There is something I can't seem to understand. On one hand light is an electromagnetic wave, as in made up of electric and magnetic fields moving through space. On the second hand it is said to create the electric field, by quantum electrodynamics. Don't these 2 heavily contradict each other ?

 

 

So what?

 

So the theory of fluids regards hydraulic fluid as incompressible when you are designing a braking system, but compressible when you are measuring the displacemment of the piston to micrometres.

 

So if you are designing an antenna to pick up radio Denver then your EM wave theory is more than adequate, but if you want to discuss Bremstralung then perhaps QED is the better option.

 

It's horses for courses mate.

[ajb]

On one hand light is an electromagnetic wave, as in made up of electric and magnetic fields moving through space.

Yes, this is the classical description based on Maxwell's equations.

 

 

On the second hand it is said to create the electric field, by quantum electrodynamics.

The electromagnetic field, and so photons, are not electrically charged. They do not act as sources of the electromagnetic field. So I think you have misread or misunderstood something.

 

 

 

Maybe you are confused about the two descriptions of light, one as a wave (classical) and one as a particle (quantum)?

[Eldad Eshel]

So how does the electric force work according to QED ? Isn't it photons or virtual photons pushing or pulling other particles ?

Edited February 23, 2016 by Eldad Eshel

[Mordred]

No how QED handles fields is based upon the gauge boson (exchange particle for electromagnetic force).

 

This is the photon, but the photon itself has no charge itself it merely exchanges the charge from one charged particle to another.

 

An electromagnetic field is comprised of a virtual (off shell ) photon at every point in space, first you set a baseline value for that field (zero or non zero). Then introduce your influence (charged particles).

 

The photon being the mediator boson transfers the charge from one particle to the other on that field.

 

But in itself the photon causes no direct influence upon the field ( other than its role as the mediator boson)

[Sensei]

So how does the electric force work according to QED ? Isn't it photons or virtual photons pushing or pulling other particles ?

In the case of electrons flowing through wire, you have difference in voltage (electric potential difference) between one region and other region of wire/electrode.

Take breadboard, plug two-three resistors, their ends connect together, in series, connect battery to their ends.

Start measuring voltages. Between end points, where battery is connected you have U.

And between resistors, U₁, U₂ and U₃.

U₁+U₂+U₃=U

Sum of voltage drop on resistors, is equal to total voltage on battery electrodes.

Voltage drop also tells you how much energy is lost/dissipated on the element. P₁=I*U₁ P₂=I*U₂ P₃=I*U₃

Power multiplied by time is energy E=P*t

Current multiplied by time is charge Q=I*t

so overall is

E₁=Q*U₁

E₂=Q*U₂

E₃=Q*U₃

E=E₁+E₂+E₃

Q divided by e = 1.602176565*10^-19 C, is quantity of electrons, flowing through our circuit.

Electrons while passing through wire and resistors lose part of their kinetic energy, and decelerate.

This additional energy appears as heat, and sometimes as photons when electron passed through metal placed in f.e. vacuum (or close to it low pressure inert gas), like it happens in light bulb.

Thus electronics elements that have to dissipate a lot of energy have heat sink, pinwheel, refrigerator.

 

If you rub material on medium such as metal, and get rid of electrons, and move them further, like it's done in electrostatic machines, these electrons can gather on electrodes.

The further they're from opposite charge electrode, the more you can gather them, the higher voltage difference will be created.

After gathering enough electrons (abundance of electrons, negatively charged), and making "holes" on opposite end (absence of electrons, positively charged).

Positive electrode is starting "stealing" electrons from medium, between them.

It's visible as coronal discharge, such little thunderbolt.

It goes through (normally non-conductive) medium, atom by atom, and finally there is electric arc between them, and discharge of electrodes.

Unless there is easier route, such as conductor, electric/electronic circuit etc.

 

 

This is the photon, but the photon itself has no charge itself it merely exchanges the charge from one charged particle to another.

[...]

The photon being the mediator boson transfers the charge from one particle to the other on that field.

You mixed something. Neutral particle exchange charge? It exchange energy.

Absorbed photon increase temperature, internal energy, in atoms that absorbed them.

Charge of particles that emitted photon, and absorbed photon, remain the same.

Edited February 24, 2016 by Sensei

[Mordred]

Good catch I did miss that aspect, long work day and just flew home. Should have just used the term mediates charge but doesn't carry charge itself.

Edited February 24, 2016 by Mordred

[Eldad Eshel]

Has there been any success in connecting the electromagnetic forces to the bending of spacetime ?

[Mordred]

All forms of energy can in effect attribute to spacetime curvature via the stress energy/momentum tensor.

[ajb]

Has there been any success in connecting the electromagnetic forces to the bending of spacetime ?

Einstein–Maxwell–Dirac equations...

[Eldad Eshel]

according to general relativity bending of spacetime causes attraction, can it cause repelling as well ?

[ajb]

according to general relativity bending of spacetime causes attraction, can it cause repelling as well ?

In some exotic situations yes. For example in the presence of exotic matter one can have repulsive gravity.

Edited February 25, 2016 by ajb

[Eldad Eshel]

Can the electromagnetic forces be described by spacetime bending ?

[swansont]

Can the electromagnetic forces be described by spacetime bending ?

 

 

A problem with that, as I understand it, is that it works for gravity because gravitational charge (i.e. mass) and inertial mass are identical. So mass can tell space how to curve, and space can tell mass how to move, as they say. But for EM, you have electrical charge, which is not equivalent to mass.

[Eldad Eshel]

Maybe electric charge also contorts spacetime, but in differents ways than mass alone, and at stronger rates, as to give the results of electromagnetism. Creating not just attraction but also repelling.

[DrP]

Is that what the Philadelphia experiment was supposed to be all about?

[swansont]

Maybe electric charge also contorts spacetime, but in differents ways than mass alone, and at stronger rates, as to give the results of electromagnetism. Creating not just attraction but also repelling.

 

 

But how do you get F=ma to work? An electron and a positron will not behave the same in the presence of a given charge distribution.

[ajb]

Can the electromagnetic forces be described by spacetime bending ?

Not space-time bending, but we have a similar understanding by using U(1) principle bundles, their connections and curvature. Without any details, the same sort of mathematics comes up in general relativity as classical electromagnetism: differential geometry.

 

Maybe electric charge also contorts spacetime, but in differents ways than mass alone, and at stronger rates, as to give the results of electromagnetism. Creating not just attraction but also repelling.

This I think would break the equivalence principal, as swansont states in one form.