What is a Charge? Exploring Positive & Negative Ions

[AudioFlux]

what is a "charge"?

hi,
what exactly is a charge? how do you define it? why is a positively charged ion at a higher potential difference than a negatively charged ion? why is work needed to be done on a positively charged ion to move it out of an electric field of another positively charged ion?

i'm very confused with electricity, and i hope i can understand it better if these doubts get cleared :)

thanks in advance

 

[mrspeedybob]

See this, I think it will shed some light on your questions.

 

[Zentrails]

hi,
what exactly is a charge? how do you define it? why is a positively charged ion at a higher potential difference than a negatively charged ion? why is work needed to be done on a positively charged ion to move it out of an electric field of another positively charged ion?

i'm very confused with electricity, and i hope i can understand it better if these doubts get cleared :)

thanks in advance

Nobody understands charge. We can only describe it, indirectly.

In fact, the entire universe is composed of energy, but nobody has the foggiest idea what regulare energy actually is, much less "dark energy" if that exists. That's why physics is great fun. You can make up the most outlandish theory you want and nobody can prove you wrong. They can only present an argument against your theory.

 

[Drakkith]

Nobody understands charge. We can only describe it, indirectly.

In fact, the entire universe is composed of energy, but nobody has the foggiest idea what regulare energy actually is, much less "dark energy" if that exists. That's why physics is great fun. You can make up the most outlandish theory you want and nobody can prove you wrong. They can only present an argument against your theory.

I think you should look up the definitions of energy and scientific theory. One cannot simply make up theories, they must have very good reasons.

 

[Drakkith]

hi,
what exactly is a charge? how do you define it? why is a positively charged ion at a higher potential difference than a negatively charged ion? why is work needed to be done on a positively charged ion to move it out of an electric field of another positively charged ion?

i'm very confused with electricity, and i hope i can understand it better if these doubts get cleared :)

thanks in advance

A charge is simply the force produced by a charged particle on other charged particles. Electromagnetic charges have a + and a -, aka postitive and negative.

A positive ion that is moved out of an electric field of another ion is having work done to it by that ion. Or more accurately both ions repel each other, performing work on each other and transforming potential energy into kinetic energy.

See here for more info: http://en.wikipedia.org/wiki/Electric_charge

 

[James A. Putnam]

Electric charge is a theoretical given. It is an unexplained starting point for theoretically explaining special effects. Theoretical explanations may or may not be correct. They are educated guesses. No one knows what electric charge is. We do know a great deal about its effects. Those effects are seen as patterns in changes of velocity. We know neither the origin of electric charge or of polarity.

James

 

[Drakkith]

Electric charge is a theoretical given. It is an unexplained starting point for theoretically explaining special effects. Theoretical explanations may or may not be correct. They are educated guesses. No one knows what electric charge is. We do know a great deal about its effects. Those effects are seen as patterns in changes of velocity. We know neither the origin of electric charge or of polarity.

James

Please, don't start this again, you will only confuse the OP and others even more. We have a definition of charge which explains what the OP is asking. I suggest you defer to that unless someone wants to talk about theoretical physics or something.

 

[JaredJames]

Electric charge is a theoretical given. It is an unexplained starting point for theoretically explaining special effects. Theoretical explanations may or may not be correct. They are educated guesses. No one knows what electric charge is. We do know a great deal about its effects. Those effects are seen as patterns in changes of velocity. We know neither the origin of electric charge or of polarity.

James

Third thread in a row, really? And you ask why they get closed down.

The terms under physics are clearly defined, especially what the OP is asking.

 

[Dickfore]

A charge is a coupling constant characterizing the interaction between matter fields with the electromagnetic field.

 

[granpa]

you can think of charge as where the electric field lines end

 

[AudioFlux]

thanks for your responses. let me elaborate my question, when we say an electron has a charge of -1.60217646 × 10-19 coulombs, what does it mean? is it like some sort of an energy or a virtual "thing"(or assumption) or is it something you can weigh?

 

[Drakkith]

thanks for your responses. let me elaborate my question, when we say an electron has a charge of -1.60217646 × 10-19 coulombs, what does it mean? is it like some sort of an energy or a virtual "thing"(or assumption) or is it something you can weigh?

The coulomb (symbol: C) is the SI derived unit of electric charge. It is defined as the charge transported by a steady current of one ampere in one second.

The problem with measuring charge, is that the closer you get to the particle the larger the force is. So instead of just saying the force is X amount at X distance, it was defined by the number of charged particles that move across a point when 1 volt is applied for 1 second.

 

[ZealScience]

Charge is just a name to describe the properties of electrostatic interactions. Just like mass, what can you say about mass?

Positive charges do work when they move closer is due to the electrostatic repulsion between charges. When forces move a distance in the direction work is done. Again you cannot explain why, just like why gravity is always attractive? Yes, you can use quantum mechanics (Relativity also for gravity) and string theory, but still you cannot explain quantum mechanics.

thanks for your responses. let me elaborate my question, when we say an electron has a charge of -1.60217646 × 10-19 coulombs, what does it mean? is it like some sort of an energy or a virtual "thing"(or assumption) or is it something you can weigh?

Coulomb is just a SI unit from convention, derived from Ampere defind by Ampere times second. Again and again you cannot ask why, just like asking what does it mean by I have mass of 60kg. It's just measured using the unit. If you use a banana to describe the charge of a proton, then electron just have -1banana of charge. It's just a relative measure used to compare the property of objects.

 

[granpa]

thanks for your responses. let me elaborate my question, when we say an electron has a charge of -1.60217646 × 10-19 coulombs, what does it mean? is it like some sort of an energy or a virtual "thing"(or assumption) or is it something you can weigh?

it means that that is how many electric lines of force end at that point

each line can be thought of as having a tension along its length and it repels all other lines.

all lines must end at charges.

http://www.google.com/search?q=electric lines of force
http://en.wikipedia.org/wiki/Line_of_force

 

[Zentrails]

I think you should look up the definitions of energy and scientific theory. One cannot simply make up theories, they must have very good reasons.

OK, here's what WIKI says:
https://secure.wikimedia.org/wikipedia/en/wiki/Energy

There doesn't seem to be any "scientific theory of energy."
Energy is an abstract concept that helps us conceptualize theories based on the results of scientific experiments.
Theories do one thing and one thing only: they predict future events.
It's not what you are taught in high school, but that's the truth about theories.

Nobody has the foggiest idea what energy actually is.
That's not a theory, it's an opinion.

 

[ZapperZ]

Please do not CHANGE this thread into ANOTHER ad nauseum thread on "what is energy?".

Zz.

 

[Zentrails]

Please do not CHANGE this thread into ANOTHER ad nauseum thread on "what is energy?".

Zz.

OK, sorry.

 

[Zentrails]

delete, dupe

 

[James A. Putnam]

"...A charge is simply the force produced by a charged particle on other charged particles. ..."

Electric charge is not a force. Coulomb's equation defines electric force. Electric charge appears in that equation as a part of that which is believed to produce electric force. Electric charge is not understood and that is why it is one of the indefinable properties of physics along with distance, duration, mass, and temperature.

James

 

[Drakkith]

"...A charge is simply the force produced by a charged particle on other charged particles. ..."

Electric charge is not a force. Coulomb's equation defines electric force. Electric charge appears in that equation as a part of that which is believed to produce electric force. Electric charge is not understood and that is why it is one of the indefinable properties of physics along with distance, duration, mass, and temperature.

James

No, do NOT start this again. Charge IS defined in science:
Electric charge is a physical property of matter which causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative.

That IS what it is. If you want to talk about what it is or isn't go somewhere else.

 

[James A. Putnam]

"Electric charge is a physical property of matter which causes it to experience a force when near other "

This is a description of a fundamentally 'given' property. It is not an explanation of what it is. There is no explanation. It is simply there and cannot be defined in terms of previously existing properties. We have good reason to believe in its existence because of definite, repetitive, special patterns in changes of velocity for some particles. You said it was 'the force'. It is not a force.

James

 

[Vanadium 50]

There is nothing in nature that is not described by its properties. "Charge", "dog", "evaporation", all are described by their properties. There's no difference.

 

[Dale]

It is simply there and cannot be defined in terms of previously existing properties.

It can be defined in terms of gauge symmetry per Noethers theorem.

 

[James A. Putnam]

There is nothing in nature that is not described by its properties. "Charge", "dog", "evaporation", all are described by their properties. There's no difference.

This does not disagree with or counter what I have said.

James

 

[vanesch]

I'll give you my 2 cents.

In fact, I still have a vague souvenir of having had questions like the OP, and then this got slowly brainwashed out of me, like by drinking Dyonisos' wine, but it still comes to me in my dreams

It's about the transition of a pre-scientific apprehension of things, with or without some mystical flavor to it, and the (erroneous) conception of science (as a kind of Revelation) that goes with it, and the bare bones actual science that you learn afterwards (if you decide to do so).

It might be very disappointing, but in fact, each time in science, especially in physics, when you ask what something "really is", you'll get two kind of answers:

- this is how we measure it / this is how we observe it / this is what it does
- this is the mathematical concept by which we define it in this theory

depending on whether you're experimentally or theoretically inclined.

You'll never hear, to your great frustration, that Charge is the yellow stuff that came out of the Right Ear of the God Coulombys when he made love to the Goddess Sparkina at the beginning of the world and permeated the universe or something.

What you'll find out is that people introduced the concept of "electrical charge" to explain a phenomenon which was electrostatic repulsion and attraction. They saw that you could associate a *number* to a piece of matter and that that number could be used, together with distance, to quantify the electrostatic repulsion. What that number stood for was not said. It was just the number that could be associated to matter to explain a phenomenon: electrostatic repulsion.
An arbitrary but clearly stated "calibration" was introduced to define the scale, or the unit, of that number.
Later it was found out that there were other phenomena, and that that *same* number turned up. From that point on, "charge", or the number we originally associated with a piece of matter to explain one phenomenon, namely, electrostatic repulsion, became a concept by itself, that was a "property" of matter, and that entered into several descriptions of several phenomena.
Several theories describe, on several levels of "microscopicity" and on several levels of sophistication, matter, and several of them use a mathematical quantity, namely a number, that they define as "electrical charge". It is used in circuit theory, it is used in electrostatics (Coulomb law), it is used in classical electromagnetics (Maxwell theory), it is used in quantum field theory... and although details can sometimes differ, it is grossly always about the same "stuff" we're talking.

So charge gets a kind of individual life of its own: it is clearly "something" that is physically meaningfull, as it enters the quantitative description of several different phenomena, and it enters several theories of physics in a kind of "unity".

But at no point, we say anything about what IS charge, except for all of this together: it is a number that is associated to matter and appears in the explanation of several phenomena, and it is a theoretical concept that is "robust" against the change in theoretical description level, so it must represent something with a strong physical meaning.

And that's it.

For some physical concepts, we can go further, because our biological senses have given us a primitive apprehension of it, a concept we already possessed since our early childhood. "Space" or "distance" is such a concept. "speed" is another one. But for charge, we don't have such a "pre-intellectual" primitive understanding, so we have to "build" one with the myriad of properties and theoretical constructs which differ in detail, but all point to a common physical "reality" of the concept at hand.
And that's the best we can do, contrary to what we (I ?) thought science would be teaching me when I didn't know any of it.

To "unlearn" or to "brainwash" yourself so that you can accept that physical concepts are nothing else but a cloud of properties and some persistent concepts in "nested" theories, or at least, that you won't know more than that about it, is an important conceptual step in becoming a physicist I'd say.

 

[James A. Putnam]

"I'll give you my 2 cents."

I read this messages more than once. I see nothing wrong with it. It was good to read.

James

 

[AudioFlux]

thank you, i understand it better now :)

 

[Drakkith]

Excellent vanesch! I wish I had your skills when it comes to explaining things.

 

[Antiphon]

Iron and oxygen really are described by their properties. But clearly there's a lot of internal structure and additional physics that leads to these properties.

The question is better asked as "what if anything is known about how a charge does what it does?"

 

[Neandethal00]

Iron and oxygen really are described by their properties. But clearly there's a lot of internal structure and additional physics that leads to these properties.

The question is better asked as "what if anything is known about how a charge does what it does?"

Can we define charges as "a Property of matter"?

Neutral particles are simply thhe result of equal amount of positive and negative charges in matter, not void of charges.

Charges can not exist withoout a carrier (matter) is another indication of charge as a property of matter.

 

[Zentrails]

It's about the transition of a pre-scientific apprehension of things, with or without some mystical flavor to it, and the (erroneous) conception of science (as a kind of Revelation) that goes with it, and the bare bones actual science that you learn afterwards (if you decide to do so).

To "unlearn" or to "brainwash" yourself so that you can accept that physical concepts are nothing else but a cloud of properties and some persistent concepts in "nested" theories, or at least, that you won't know more than that about it, is an important conceptual step in becoming a physicist I'd say.

I think that is correct. The ancient Greeks were aware of charge, they had various ways of inducing it, including rubbing fur against an insulator of some source. They also used lodestones. They obviously observed static electricity and probably noticed the similarity to lightning bolts.

They accepted them as real (probably magical) things without trying much to figure out what caused them. They were probably considered strange and mysterious substances. My HS Biology teacher used to say, "Never ask why, no one knows why," but that was over 40 years ago. Since then I think we are starting to answer why.

 

[mquirce]

neandethal100. Well There are people that don.t like idea of particles of matter as the only reality in the structure of everything that exist in the universe. Like you , share the concept of charges as the ability of particle of mater to atract or repel the same kind of partner, and together with gravity( another ability of particle of mater) are in the structuire of particles
elementare (mass or massles) and in all complex particles.The fields nd the electromagnetic waves are extention of this ability in space, allways toward a center that is the particle of mater.A crackpot idea? Maybe! We are in a status that nothing is worth for trust.
Sorry about the confusion ofn olld layman.

 

[vanesch]

I think that is correct. The ancient Greeks were aware of charge, they had various ways of inducing it, including rubbing fur against an insulator of some source. They also used lodestones. They obviously observed static electricity and probably noticed the similarity to lightning bolts.

They accepted them as real (probably magical) things without trying much to figure out what caused them. They were probably considered strange and mysterious substances. My HS Biology teacher used to say, "Never ask why, no one knows why," but that was over 40 years ago. Since then I think we are starting to answer why.

I'd say, that's because we're forgetting again the important lessons of physics versus theology, and indeed, sometimes I have the impression that people are going back to this "theological" status of affairs in theoretical physics (my own opinion, not worth 2 cents here ).

I still think that what we call a concept in physics of which we think/have the impression/are convinced/... that we know WHAT it is (and worse, why it is so), is nothing else but a cloud of properties, mathematical definitions in the frame of theories, and links with other concepts. If that cloud is "thick" enough, we feel that we know what it is, and that we are in a way familiar with it. But in fact we don't know really what it is and certainly not why it is so, except in the frame of this cloud of properties and links.

And there's nothing wrong with it, except that this is not usually what we think we mean by "what" and "why" in a more absolute sense.

Feynman said once that a good physicist knows something when he can describe it at least in 7 different ways. I think there's a lot of truth in that statement (I'm playing on the safe side with Feynman here ).

I suppose he meant, that if someone asks a good physicist "what is charge ?" that the good physicist can think of several ways of answering that question (and then getting into arguments with people who think there's one unique, absolute answer to that question and gets in a row over at least 6 of his 7 answers). I suppose that what Feynman was saying was, that a good physicist has a "cloud of properties and links" in his mental construct of what he understands charge to be, and that he can explore that at will:

- it is a property of matter
- it is something that repells other charges
- it is a quantum number of elementary particles
- it is a source of the electrical field
- the thing that, when it flows, gives you electrical current
- a conserved number
- a generator of an abelian gauge field
...

and then you can enter a theological discussion of which of these things is "really" what charge is. In fact, these are all part of that conceptual cloud, with its theoretical definitions in the frame of certain theories, and with links to other concepts, and if that cloud is sufficiently "rich" we feel comfortable with knowing what we're talking about when we use the concept of charge.

In a certain context, certain elements of that cloud are of course more relevant than others, and a good physicist knows what is relevant to a certain context and what is not going to help her.

Of course, the answer to the "why" question is somewhat similar. Why does this piece of matter attract that piece ? - well, because there is electrical charge on it !
Why does a proton attract an electron ? - because they are charged ?
Why is an electron charged ? - Because it fills in a place in the standard model where there is a coupling to the electromagnetic potential...

But all these answers really simply follow links between conceptual clouds, they are not a real, theological answer to the why question: Why did this happen ? Because your favorite god wanted it to be so.

When people in science try to answer fundamental "why" and "what" questions, I think they are falling back on the pre-scientific, mystical way of looking at the world. You can of course gain "deeper understanding", by having a new, underlying, more general theoretical framework that helps you moreover to establish more links between previously unconnected concepts (also called "unification" ), but it only shifts the "why" and "what" questions to a deeper level.

In the mean time, we're happy as scientists, because we've enriched our "conceptual clouds" of known things, and added a few new ones (and maybe realized that a few others became "superfluous" except maybe on a practical level - such as in continuum mechanics).

 

[valeriy2222]

You can watch a lecture on youtube. In there is a simple and good description about fields and charges.

walter lewin
Lec 1 | MIT 8.02 Electricity and Magnetism, Spring 2002

 

[Zentrails]

I'd say, that's because we're forgetting again the important lessons of physics versus theology, and indeed, sometimes I have the impression that people are going back to this "theological" status of affairs in theoretical physics (my own opinion, not worth 2 cents here ).

I agree with that. Religion answered those questions for years. "The earthquake happened because we've displeased <insert favorite diety here/>" A world were bad things happened suddenly, without warning, and for no apparent reason would be a very scary world to live in.

We don't want to go there with science. My HS biology teacher was rarely wrong, so he is probably still right to say, "Don't ask why."

I also tend towards Buddhism (my wife is Korean and a Buddhist of sorts) a little but find people who claim that Quantum Mechanics proves Buddhist principles somehow to be really annoying. Mixing religion and science is a good way to start a fist fight. LOL