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Charge - what is it?

  1. May 30, 2009 #1
    Charge -- what is it?

    Analogous to understanding of gravity in the days before Einstein, I know the effects of Charge and can even feel it, but have no idea what it is.

    Well, I know electrons are negativly charged and protons positively. I know the effects of charges; atoms with excess of electrons are negative ions and deficiency plus ions. I know like charges repell and counter attract. Apparently charge is a Force that can be expressed as derivation of basic equation F=ma (one would think) since, given sufficient coulombs of force, C, it can move a mass, m. I even gamble to say that there is a conservation of charge too. I guess these are well defined observations but still I am at a loss what charge is. Therefore I put you guys in charge, :tongue:, of helping me understand.

    I put together these questions and if someone answers them I think I will be closer to understanding it;
    1) What properties of electrons lends them a minus charge
    2) What properties of protons lends them plus charge.
    3) Can it be shown that neutral particles such as neutrons lack these properties.
    4) How is a charge transmitted (what is electromagnetic force made out of better question?)
    5) The strong nuclear force prevents protons from blowing appart the atom; but likewise, what is keeping the many electrons from doing same (why don't electrons throw each other out of orbit?). I know of coulomb force of attraction but I would think that it alone can not produce needed forces. One would think there would also need to be angular velocity, centripetal force, to create equilibrium, else electron would fall into nucleus. But would this imply electron is a particle or can a wave also have angular velocity?

    Those are my questions about Charge I hope it's not to many.

  2. jcsd
  3. May 30, 2009 #2
    Re: Charge -- what is it?

    First of all, charge is NOT a force. A charge can apply a force on another charge though, but that is another story.

    Charge is simply a property of some elementary particles. The electron is a particle that simply has a negative charge. The proton is a particle that has the same, but positive charge. We cannot say anything more than that, charge is simply a property of the particle, just like mass.

    So questions 1, 2 and 3 don't really make sense. Charge IS the property.

    4) You seem to mean the force between two charges. That force is electromagnetic. The photon is the force carrier of electromagnetic fields.
    'The charge' cannot be transmitted from one particle to another. However, you can 'transmit' electrons (for example) from one object to another. This is often called charge transmission, but it is really just electrons moving. The charge is still in the electrons.

    The electrons are kept in orbit by the positive charge of the nucleus. They do repel each other slightly, which becomes more important when you get more electrons. This repulsion is probably also the reason that there are no ions with, say, 10 more electrons than protons; such ions are simply not stable, the nucleus' attractive force on the electrons is simply not strong enough.

    Why electrons don't fall into the nucleus is a fairly complicated subject. Physicists have struggled with it for a long time (back in the day when electrons were still thought to circle the nuclear like planets around the sun).
    If you google this you will probably find more than you want...!
  4. May 30, 2009 #3
    Re: Charge -- what is it?

    hmm, I can't accept that a Charge is simply a property. There has to be a reason electrons are negative and protons positively charged. Just saying it's a property is like saying God created the heavens and it's blasphemy to wonder there origins.

    Can anyone tell me what charge is other than a property?
  5. May 30, 2009 #4
    Re: Charge -- what is it?

    There might be a reason, but we don't know it. In our current understanding, electric charge is a fundamental property of some particles.
  6. May 30, 2009 #5


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    Re: Charge -- what is it?

    Like Nick89 says, what is mass?

    Charge is a fundamental property. This means it cannot be derived from anything else. It just is. We accept it as a postulate of sorts for physics. The same holds true for mass.

    You can talk about subatomic particles, quarks, etc. if you like, but eventually you run into the same problem.
  7. May 30, 2009 #6


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    Homework Helper

    Re: Charge -- what is it?

    Well one could say (I think) that charge is a conserved quantity resulting from gauge invariance.
  8. May 30, 2009 #7
    Re: Charge -- what is it?

    What is mass? I would define it as the measure of the aggregation of atomic particles that react to and effect gravitational fields. I have the ingredients for mass, atoms, but troublesomely the converse for charge.

    Well, hopefully, CERN will yield answers as they unravel internals of atom with their localized version of big bang.

    It feels like a step backwards to say Charge is due to God, I mean fundamentals, because frankly, if you can't explain the fundamentals you have no chance of ever creating a theory of everying or understanding the "Big Picture"; the big picture is created by them!. Maybe this is reason science is currently at an impasse with atom and why standard model is broken.
  9. May 30, 2009 #8
    Re: Charge -- what is it?

    So why can't you accept the same for charge? You could define charge as the measure of how particles react to and effect electromagnetic fields. Exactly the same thing!
    Just like there are massless particles (photon) there are also charge-less particles (neutron). The similarities only break down due to the fact that mass comes only in positive quantities, whereas charge does not.

    Nobody said anything about God.

    You don't seem to like the idea of something being a fundamental property. If you don't want to believe in anything being fundamental, then how can anything exist at all?? Surely something must be fundamental? Whether or not it is charge, we cannot say for sure at the moment. In our current understanding however, charge is fundamental, and as far as we can measure, experiments agree with that idea.

    As soon as someone comes along and shows an experiment that shows that charge is not fundamental, we will know that we were wrong. That day however has not come yet.
  10. May 30, 2009 #9
    Re: Charge -- what is it?

    Charge is always associated with mass. Classically, charge is equal to the divergence of an electric field. Charge is measured in discrete units. Classically, charge conservation can be attributed to the properties of electromagnetic fields and spacetime.
  11. May 30, 2009 #10
  12. May 30, 2009 #11
    Re: Charge -- what is it?

    Why can't you just say it's a quantity of electrostatic force (either + or -).

    This might be a 'deeper', more meaningful definition.
    Last edited: May 30, 2009
  13. May 30, 2009 #12
    Re: Charge -- what is it?

    Well, for mass and gravity, the late Professor Albert Einstein wrote E=mc^2 and explained the concept of spacetime warping. Where as for Charge I guess one has "that's the way it is so don't worry about it". There is certainly no sameness there.

    It's not that I don't like the idea but simply put "I want to understand it". Maybe it's against the scientific paradigm, but in my opinion even fundamentals, namely charge, should be subject to the same scientific conjecture and scrutiny as the greater whole.

    Maybe charge is result of a particles spin. Perhaps some particles can warp/unwarp some higher dimension of space resulting in what we perceive as attraction/repulsion (+-charge), similar to way mass creates gravity in 4D spacetime.

    Ultimately, I know there is a mechanism behind "charge" and even though it's a so called basic property, there is no reason it is beyond comprehension.
    Last edited: May 30, 2009
  14. May 30, 2009 #13
    Re: Charge -- what is it?

    To the OP

    I sounds like you have your thesis topic
  15. May 30, 2009 #14
    Re: Charge -- what is it?

    Thanks, this kind of clears things up for me. Well, attraction and repulsion is result of exchange of bosons particle. And this exchange produces energy and momentum which I assume is force that does repulsing and attracting. It appears that my question "What is charge" is deeply embedded in quantum mechanics and does meaning and not just taken as fundamental.
    Last edited: May 30, 2009
  16. May 30, 2009 #15
    Re: Charge -- what is it?

    Charge is a fundamental attribute associated with matter & energy. An electron has a charge of -1. A proton has +1, & a neutron has 0.

    But a proton is made up of 2 up quarks & 1 down quark. A neutron is 1 up quark & 2 down quarks. An up quark has a charge of +2/3. A down quark has a charge of -1/3.

    Does this help?

  17. May 30, 2009 #16
    Re: Charge -- what is it?

    no, that doesn't. I'm reading up on bosons, leptons, fermions and such. I think I will get understanding from it. Then, I will post summary and maybe demonstrate how I can use what I learned with equations. should be fun!
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