What is Charge?

[XM5ER]

I know a car website might not be the best place to ask this question but we have had a few geniuses post here in the past.

So, whilst helping my daughter revise for a chemistry test last night we were looking at relative charge and relative mass and atomic numbers. After accepting that orbits and shells of electrons is just a model and not what is really going on (to be fair her teacher had mentioned this also) she asked me the fundamental question "so, what is charge"?

My answer, I don't know. I know we can measure it, I know it is a property of protons and electrons and that their charge's are opposite and attract but, what is it? I appreciate that quantum physics is not readily explained in english but can anyone have a stab at this?

[Eric Mc]

Charge is a property of atoms. It is linked to the balance between the charges held by the protons and electrons in the atom.

The outer shell of an atom is composed of electrons which possess an electric charge. The nucleus contains protons which also have an electric charge. We describe the electron's charge as being "negative" and the proton's as being "positive". Normally the two charges balance out so the atom will overall have a neutral charge. However, if the number of electrons is altered (which can be done fairly easily - by rubbing, polishing, atmospheric conditions etc.), the number of electrons in the outer shell my differ. If they are in excess, then the atom becomes negatively charged and if reduced, it becomes positively charged.

I suppose all we can say is that charge is a property. It's something we observe these particles to have.

[XM5ER]

Thanks for having a stab Eric but you've not really said anything different to what I already had. I get that charge is an arbitrary value assigned to a property of subatomic particles. But what actually is it and why does it behave like it does? I think maybe that I need to tweet Lawrence Kraus.

[Eric Mc]

Does anybody know?

Sometimes, what is, just is.

[XM5ER]

That's more or less what I said to my daughter But it is an intriguing question.

[deckster]

Charge is a fundamental property of subatomic particles, and can't really be explained in terms of anything else. In a very real sense, charge just is. The universe wouldn't work at all well without it, for a start.

If it helps, https://physics.info/standard/ has a pretty good and reasonably understandable summary.

Website said:

Charge is the property of matter that gives rise to electric and magnetic phenomena (known collectively as electromagnetism). Charge is quantized, which means it can only exist in discrete amounts with restricted values — multiples and fractions of the elementary charge (e = 1.6 × 10−19 C). Particles that exist independently (the electron, muon, and tau) carry multiples of the elementary charge (−1e), while quarks carry fractions of the elementary charge (+⅔e or −⅓e). Quarks always bind together in groups whose total charge is an integral multiple of the elementary charge, which is why no one has ever directly measured a fractional charge. In addition, since opposite charges attract, electrons tend to bind to protons to form atoms that are neutral overall. We don't normally notice the electrical nature of matter because of this.

Charged particles interact by the exchange of photons — the carrier of the electromagnetic force. Whenever an electron repels another electron or an electron orbits a nucleus, a photon is responsible. Photons are massless, uncharged, and have an unlimited range. The mathematical model used to describe the interaction of charged particles through the exchange of photons is known as quantum electrodynamics (QED).

[Simpo Two]

For GCSE/A-level purposes Eric's answer is perfectly good. Just know that electrons are -ve and protons are +ve, opposites attract and nature likes to cancel them out.

[nammynake]

I am reminded of this interview with Feynman (discussing magnetism, not charge)...

https://www.youtube.com/watch?v=MO0r930Sn_8

[FredClogs]

It's just a potential difference, in electronics the unit Volts is a measure of the potential difference in energy (electrical) between one place and another. A "charge" is just that, a word to describe the potential difference in energy between two "things"

[XM5ER]

nammynake said:

I am reminded of this interview with Feynman (discussing magnetism, not charge)...

https://www.youtube.com/watch?v=MO0r930Sn_8

I love the way he rips the interviewer for asking a poor first question, can you imagine having him as a tutor.

So it comes back to part of my original question, in that charge cannot be explained readily in an English language frame of reference. These are the kind of questions that make me regret going down the engineering route when my heart was in physics. Never mind.

I think the problem of charge comes from viewing electrons and protons as discrete particles rather than wave functions. If you view them as wave functions you can begin to see how attraction and repulsion can work at a more fundamental level. The next problem becomes, what is the field on which the waves act?

[Einion Yrth]

I fear that once you enter the "what is" mode of thought madness lies soon after...
what is;

inertia
spin
gravity

and so on. We can calculate with reasonable effectiveness loads of stuff, but do we really know what they are? Is it even a meaningful question?

[CanAm]

From another thread I got pointed towards the FES Website. Flat Earthers don't believe in gravity either; apparently, things "just fall".

A bit simplistic, but maybe there's something to be said for accepting things the way they are rather than worrying about sub-atomic particles to the point where your brain hurts.
Discuss.

[James_B]

Eric Mc said:

Does anybody know?

Sometimes, what is, just is.

It’s the measure of the strength of interaction with the electromagnetic force, just one of the many quantum numbers that a particle can have, such as mass, spin etc.

So it’s hard to say what it “is” beyond this, really. We can say in great detail what it means, but you are entering into the realms of philosophy at the moment if you delve too much deeper.

[James_B]

FredClogs said:

It's just a potential difference, in electronics the unit Volts is a measure of the potential difference in energy (electrical) between one place and another. A "charge" is just that, a word to describe the potential difference in energy between two "things"

No, it’s not that at all. Potential difference refers to distance down an electric gradient.

[FredClogs]

James_B said:

FredClogs said:

It's just a potential difference, in electronics the unit Volts is a measure of the potential difference in energy (electrical) between one place and another. A "charge" is just that, a word to describe the potential difference in energy between two "things"

No, it’s not that at all. Potential difference refers to distance down an electric gradient.

The questions is "What is charge" not "How do weird maths geeks express the world around them" there's nothing to be gained by laymen talking about wave functions and line integrals, you can get through life being a perfectly productive engineer or scientist knowing that voltage is the units of stored electrical charge i.e joules per coloumb

[hairykrishna]

FredClogs said:

James_B said:

FredClogs said:

It's just a potential difference, in electronics the unit Volts is a measure of the potential difference in energy (electrical) between one place and another. A "charge" is just that, a word to describe the potential difference in energy between two "things"

No, it’s not that at all. Potential difference refers to distance down an electric gradient.

The questions is "What is charge" not "How do weird maths geeks express the world around them" there's nothing to be gained by laymen talking about wave functions and line integrals, you can get through life being a perfectly productive engineer or scientist knowing that voltage is the units of stored electrical charge i.e joules per coloumb

The point he's making is that voltage is not charge, even in a simplified understanding.

Voltage is electrical potential energy per unit charge not 'stored electrical charge'.

[James_B]

FredClogs said:

The questions is "What is charge" not "How do weird maths geeks express the world around them" there's nothing to be gained by laymen talking about wave functions and line integrals, you can get through life being a perfectly productive engineer or scientist knowing that voltage is the units of stored electrical charge i.e joules per coloumb

Yes, the question was “what is charge”, but you were not describing charge.

Charge and voltage and electric potential are different quantities.

And no, voltage is not a unit of charge. Coulombs are, so no, you really can’t be a productive scientist or engineer if you fall down on the very basics like this.

Edited by James_B on Saturday 30th September 21:59