# What actually is charge?

1. May 13, 2005

### icvotria

What actually is charge? Hmm, I'm trying to think of a way to elaborate the question to make myself sound a bit more intelligent but I can't so I'll have to just live with ignorant and curious :grumpy:

2. May 13, 2005

### JamesU

3. May 13, 2005

### dextercioby

For a 13-yr old,i guess there's nothing more to say than:"along with rest/invariant mass and spin,one of the fundamental properties of matter".

Daniel.

4. May 13, 2005

### quasar987

:rofl:

So yes, charge seems to be amongst the most fundamental properties of matter. And by that it is meant that we can't deny its existence*, yet there is no explanation for it in terms of other concepts. It's fundamental.

*Take 3 objects, A, B and C. If A & B repulse each other and A & C attract each other, then invariably, we observe that B & C attract each other. From there, you can derive the notions of 'positively charged' and 'negatively charged'.

5. May 15, 2005

### dextercioby

For the record,there is a reasonable explanation for the existence of charge.Electric charge,that is.Within the SM of particles and interactions,of course.I dunno how particle electric charge emerges from string vibrations,i have a hunch there is a way...

Daniel.

6. May 16, 2005

### roger

Isn't she 23 ?

In the standard model, why is the electron referred to as a point charge ? Doesn't the electric field lines converge to give an infinite energy density ?

When we take the vector product of velocity and flux density,(of charge) why is the magnetic intensity equal to this ?

7. May 16, 2005

### dextercioby

Of course,i meant "Yo,mamma!".He's 13.

There's no problem with that.There's no such thing as "field lines" at quantum level.Incidentally,the energy of the electron field vacuum is taken to be zero in the theory of the Dirac field and in QED,the electron self-energy diagrams are renormalized.

As for the second,could u ascribe an equation to it ?

Daniel.

8. May 16, 2005

### roger

What did you mean theres no such thing as field lines at quantum level ?

H=vector product v *d(flux density vector)

Also, why do we assign epsilon0 permittivity to vacuum, ? what is there to resist flow of charge ?

And how does the electric potential exist in the vacuum ? it can be measured..

Roger

9. May 16, 2005

### ~()

hmmmm,
a charge quantised by QM illustrates an assembly of photons...

Is the charge around a electron a constant cloud, does it emit from the electron itself, does there need to be a picture for energy conservation ?

How do particles - the fields of EM actually work? How and why is charge able to attract - to repel, does this mean a special case for gravity since it can only attract ?

All interesting queries...

10. May 17, 2005

### roger

thankyou

11. May 17, 2005

### marlon

in most general terms, charge is a measure of how strong two charged particles interact with each other via the Electromagetic forces, like the Coulombforce for electrical charges.

So charge not only says that a particle will interact via EM-forces, it also gives an idea of how strong this interaction will be

regards
marlon

12. May 17, 2005

### quasar987

Socrates is probably cursing in his grave right now.

13. May 18, 2005

### icvotria

That's what I meant to say

14. May 19, 2005

### Haelfix

Charge is an interesting topic. I recall there being papers in the 60s (Wheeler I think) where he tried to relate charge to geometric configurations of defects (little 'effective' blackhole configurations). I think there were problems with the model, does anyone know the details?

Magnetic charge (both Dirac, Polyakov and T'Hooft monopoles) of course is completely determined by the geometry within gauge fields. They are pure topological solutions (related to the first chern class), and incidentally if observed, would imply electric charge quantization (a really cool, simple result with the so called Dirac string accessible to undergrads).

In the literature you sometimes come across various different types of electric charge. The localized, non gauge invariant quantized versions. Nonlocal, gauge invariant unquantized versions, and nonlocal, gauge invariant quantized ones.

15. May 19, 2005

### marlon

I see your point . You are indeed correct

marlon

16. May 19, 2005

### marlon

Quite right. For the Dirac string thing and quantization of both magnetic and electric charge, check out the zip-file in post nr 20 of https://www.physicsforums.com/showthread.php?t=43685&page=2&pp=15

regards
marlon

17. May 23, 2005

### cefarix

In the Standard Model the how and why of charge aren't defined...it's just an intrinsic property like spin and mass, without any cause to it. My theory does give the cause of charge, spin, and mass, but that's beyond the scope of this post of course :)

18. May 23, 2005

### cefarix

1 eV = 1.6 x 10^-19 Joules

This is the energy imparted to a charge of 1.6 x 10^-19 Coulombs by an electric field as it moves from a point that has an electric potential of 1 Volts to an point which has an electric potential of 0 Volts.

The natural unit of electric charge is 1.6 x 10^-19 Coulombs. This is the magnitude of the charge on the proton and the electron.

19. May 23, 2005

### Tom Mattson

Staff Emeritus
I've pruned the little sideshow out of this thread. Everyone at PF should keep in mind that when someone asks a question that it is safe to assume that that person is looking for a cogent, correct answer from a qualified person. If that does not apply to you then you should resist the urge to post your answer to the question.