Sha31 Posted December 10, 2009 Share Posted December 10, 2009 1.) What is the difference between electric field and electric charge? 2.) What is the difference between electric field and electron/positron? 3.) What is the difference between electric charge and electron/positron? 4.) Is there an electric field which is not the field of some electron/positron? Link to comment Share on other sites More sharing options...
ajb Posted December 10, 2009 Share Posted December 10, 2009 The short answer is that electric charges act as sources for the electric field. Link to comment Share on other sites More sharing options...
Sha31 Posted December 10, 2009 Author Share Posted December 10, 2009 Ok. Electrons, whatever they are, also act as sources of electric fields, so would you agree 'negative charge' is the same thing as electron, and that 'positive charge' is the same thing as positron? Then, what is the difference between electric field and electron? And, could there be electric field which is not in the same time a part of some electron/positron (charge)? Link to comment Share on other sites More sharing options...
ajb Posted December 10, 2009 Share Posted December 10, 2009 Ok. Electrons, whatever they are, also act as sources of electric fields, so would you agree 'negative charge' is the same thing as electron, and that 'positive charge' is the same thing as positron? No. Electron and positrons have the property we call electric charge. So do quarks and the Z-boson. The charge is the reason why they interact electromagnetically. Then, what is the difference between electric field and electron? The electric field should be viewed as (part of) a medium in which electric interactions are transmitted. It is how electrons in a metal "talk to each other". I know people have thought about electrons as a kind of solition "localised lump" in the electromagnetic field in higher dimensions. But this is not the standard view point. And, could there be electric field which is not in the same time a part of some electron/positron (charge)? At the energy scales of everyday life, all the electric and magnetic fields are due to electrons. But electrons are not the only charged fundamental particle. Link to comment Share on other sites More sharing options...
Sha31 Posted December 10, 2009 Author Share Posted December 10, 2009 No. Electron and positrons have the property we call electric charge. The charge is the reason why they interact electromagnetically. So' date=' "electron" and "single negative charge" are different things? F= k* q1*q2/r^2 "q" stands for CHARGE, it represents electric FIELD, and we use it to calculate force between two ELECTRONS. The three words seem to be quite interchangeable. In fact, I can not think of any case where there is an electric charge, that does not have electric field, which is not a part of some electron. Numerical value and location for all three of these "things" seem to be in the same spot, sharing the same place with that "q". Why is this? The electric field should be viewed as (part of) a medium in which electric interactions are transmitted. It is how electrons in a metal "talk to each other". I know people have thought about electrons as a kind of solition "localised lump" in the electromagnetic field in higher dimensions. But this is not the standard view point. Aether and solitons, I like that. At the energy scales of everyday life, all the electric and magnetic fields are due to electrons. But electrons are not the only charged fundamental particle. So, the only difference between 'electric field' and 'electron' is that in the case of electron there is some "ball" in the center that has no size? Link to comment Share on other sites More sharing options...
ajb Posted December 10, 2009 Share Posted December 10, 2009 So, "electron" and "single negative charge" are different things? F= k* q1*q2/r^2 "q" stands for CHARGE, it represents electric FIELD, and we use it to calculate force between two ELECTRONS. The three words seem to be quite interchangeable. In fact, I can not think of any case where there is an electric charge, that does not have electric field, which is not a part of some electron. Numerical value and location for all three of these "things" seem to be in exactly the same spot, sharing the same place with that "q". Why is this? In the above context they look interchangeable. But you should think of the charge as a property of an electron, it is the property that allows it to couple with the electromagnetic field. The formula you give would also work for spherical charge distributions, i.e. not single electrons. Aether and solitons, I like that. I said nothing about an Aether. So, the only difference between 'electric field' and 'electron' is that in the case of electron there is some "ball" in the center that has no size? The electric field is not the same as an electron. Electrons act as point-like sources of the electric field. The electron has properties that are not shared by the electric field. A classical example would be mass. The electric field has no mass. Electrons do. Link to comment Share on other sites More sharing options...
Sha31 Posted December 10, 2009 Author Share Posted December 10, 2009 (edited) In the above context they look interchangeable. But you should think of the charge as a property of an electron, it is the property that allows it to couple with the electromagnetic field. The formula you give would also work for spherical charge distributions, i.e. not single electrons. I said nothing about an Aether. Ok. The electric field is not the same as an electron. Electrons act as point-like sources of the electric field. The electron has properties that are not shared by the electric field. A classical example would be mass. The electric field has no mass. Electrons do. The only example I can think of where electric fields have no mass is 'photon'. What other example is there of electric field that is actually not an electron? Also, it turns out fields do have mass: - "... and the field has such familiar properties as energy content and momentum, just as particles can have." http://en.wikipedia.org/wiki/Field_(physics) Edited December 10, 2009 by Sha31 Link to comment Share on other sites More sharing options...
swansont Posted December 10, 2009 Share Posted December 10, 2009 (edited) So, "electron" and "single negative charge" are different things? F= k* q1*q2/r^2 "q" stands for CHARGE, it represents electric FIELD, and we use it to calculate force between two ELECTRONS. The three words seem to be quite interchangeable. In fact, I can not think of any case where there is an electric charge, that does not have electric field, which is not a part of some electron. Numerical value and location for all three of these "things" seem to be in the same spot, sharing the same place with that "q". Why is this? (emphasis added) Argument from incredulity. What if you have an antiproton? Or one of a number of negatively charged mesons? The terms are not interchangeable. Merged post follows: Consecutive posts mergedThe only example I can think of where electric fields have no mass is 'photon'. What other example is there of electric field that is actually not an electron? Also, it turns out fields do have mass: (Richard P. Feynman) - "... and the field has such familiar properties as energy content and momentum, just as particles can have." http://en.wikipedia.org/wiki/Field_(physics) Energy content and momentum ≠ mass Photons have energy and momentum, but no mass Edited December 10, 2009 by swansont Consecutive posts merged. Link to comment Share on other sites More sharing options...
Sha31 Posted December 10, 2009 Author Share Posted December 10, 2009 (edited) What if you have an antiproton? Or one of a number of negatively charged mesons? Ok' date=' but how do you know antiproton does not contain electrons? What is the magnitude of electric charge of meson and antiproton? Energy content and momentum ≠ mass Photons have energy and momentum, but no mass Momentum implies mass: P= m*v. Without mass momentum is zero, right? What is the value of photon momentum? How do we know (measure) photon momentum? Edited December 10, 2009 by Sha31 Link to comment Share on other sites More sharing options...
Mr Skeptic Posted December 10, 2009 Share Posted December 10, 2009 Electrons are the only negative charge you are likely to ever encounter, protons are the only positive charge you are likely to encounter. There are other charged particles as well, but for the most part you won't notice them unless you specifically go looking for them. A photon has an induced electric and magnetic field. A photon does not act as a overall source of electric field, it is not charged. A photon has energy E=hf and momentum p=hf/c. Photons have zero rest mass (and they can't be at rest anyways), but they have "relativistic mass" which when it comes down to it is just another word for energy. Link to comment Share on other sites More sharing options...
swansont Posted December 10, 2009 Share Posted December 10, 2009 Ok, but how do you know antiproton does not contain electrons? What is the magnitude of electric charge of meson and antiproton? All freely observable particles come in units of the fundamental charge. So an antiproton and e.g. a negatively charged pi meson all have the same charge, and this is confirmed to the level that we can do such experiments. We know the antiproton does not contains electrons because physicists have been successfully doing physics for a while. For an antiproton contain an electron would violate a large number of laws of physics and contradict a whole bunch of experiments. If that sounds snarky, I apologize, but this encompasses decades of physics research and it's as if you were asking, "How do you know you haven't just gotten it all wrong?" (The answer to which is "Because it all works") Momentum implies mass: P= m*v. Without mass momentum is zero, right? What is the value of photon momentum? How do we know (measure) photon momentum? For a massless particle, p = E/c Hit an atom with a photon and it will recoil. That's the basis of laser cooling, which was the subject of the 1997 Nobel prize. Link to comment Share on other sites More sharing options...
Bob_for_short Posted December 10, 2009 Share Posted December 10, 2009 1.) What is the difference between electric field and electric charge? A pointlike charge creates an electric field that acts on other charges in a ceratin way E(r) = qr/r^3. This filed can be "felt" at many points at the same time by different other charges. Note that q can be of both signs and may belong to nuclei too. 2.) What is the difference between electric field and electron/positron? See the answer above. 3.) What is the difference between electric charge and electron/positron? They are particular cases of charges. There are many other charged particles, heavy and light. 4.) Is there an electric field which is not the field of some electron/positron? Yes. If you srtip many electrons from a body, it gets positively charged due to non-compensated amount of positive charge of all nuclei and the amount of remaining electrons. This happens all the time when wind blows and separates charges between the Earth and clouds. Sudden recombination (neutralization) of separated charges is a lightning. Link to comment Share on other sites More sharing options...
Sha31 Posted December 10, 2009 Author Share Posted December 10, 2009 (edited) Yes. If you srtip many electrons from a body' date=' it gets positively charged due to non-compensated amount of positive charge of all nuclei and the amount of remaining electrons. This happens all the time when wind blows and separates charges between the Earth and clouds. Sudden recombination (neutralization) of separated charges is a lightning.[/quote'] Ok. But electron is elementary particle. It is "elementary charge", i.e. the smallest, indivisible amount of charge that can exist, right? Therefore, positron is all that too only with positive charge, yes? Are there some quarks, or whatever particles, that have smaller amount of charge than electron? If yes, then why are they not the 'elementary charges'? If not, then how do you know your quark is not actually an electron/positron? We can make a beam of electrons, can we make a beam of quarks? Can we observe quarks, or say muons, in bubble chamber? Merged post follows: Consecutive posts merged For a massless particle' date=' p = E/c Hit an atom with a photon and it will recoil. That's the basis of laser cooling, which was the subject of the 1997 Nobel prize.[/quote'] Ok. How do we know (measure) photon has no mass? What is the value of photon momentum, for say red light? All freely observable particles come in units of the fundamental charge. So an antiproton and e.g. a negatively charged pi meson all have the same charge, and this is confirmed to the level that we can do such experiments. We know the antiproton does not contains electrons because physicists have been successfully doing physics for a while. For an antiproton contain an electron would violate a large number of laws of physics and contradict a whole bunch of experiments. If that sounds snarky, I apologize, but this encompasses decades of physics research and it's as if you were asking, "How do you know you haven't just gotten it all wrong?" (The answer to which is "Because it all works") Ok, let me rephrase. You know proton is not made from positrons, you know it is made of quarks and its positive charge comes from quark's electric field instead, i.e. magnitude of electric charge. So, basically I'm asking what is the difference between quarks and electrons/positrons? And, what is the equation that describes electric and magnetic fields of quarks? Edited December 10, 2009 by Sha31 Consecutive posts merged. Link to comment Share on other sites More sharing options...
Bob_for_short Posted December 10, 2009 Share Posted December 10, 2009 Ok. But electron is elementary particle. It is "elementary charge", i.e. the smallest, indivisible amount of charge that can exist, right? Therefore, positron is all that too only with positive charge, yes? Right. It is the smallest charge that we can separate from a matter and operate with it - accelerate in accelerators, TV tubes, electronic lamps, etc. Are there some quarks, or whatever particles, that have smaller amount of charge than electron? If yes, then why are they not the 'elementary charges'? If not, then how do you know your quark is not actually an electron/positron? Quarks were invented (not directly observed) in order to: 1) explain some scattering experiments with heavy compound nuclei, 2) squeeze the quarks into a certain group of symmetry that require at the same time fractional charge of quarks (3 quarks in proton, neutron, and two in mesons) and impossibility to observe a quark in a free state. The strong interactions are so strong that one cannot separate things in a compound system without creating new coupled quarks. It is such a model in theoretical physics. Just keep in mind that strongly interacting things sometimes cannot be separated, like phonons from a solid. They are some quasi-particles - elementary excitations of compound systems. We can make proton beams that are beams of coupled together quarks. Quarks are always bound, mesons are well observed as free. Link to comment Share on other sites More sharing options...
darkenlighten Posted December 10, 2009 Share Posted December 10, 2009 Also an electron is made up of a quark and anti-quark: a Down quark and an Anti Up quark. The Down quark has a charge of -1/3 (e), where e is the charge of an electron (in absolute value) and the Anti Up quark has a charge of -2/3 (e), giving you -1 (e). And P = E/c and E = hc/lambda, where lambda is the wavelength of the photon of light, so plug in the values and you will get the answer. Also, F = (k * Q*Q')/r^2 r and the electric field is F = Q E, so Q' does not mean its an electron or whatever, its the value of charge of the particle you are talking about. This is usually also for point like charges. So for the case of an electron it has a certain charge (e) you plug that in for the value of Q' and Q is the "test charge" at which you are looking at the electric field. Link to comment Share on other sites More sharing options...
swansont Posted December 10, 2009 Share Posted December 10, 2009 Ok. But electron is elementary particle. It is "elementary charge", i.e. the smallest, indivisible amount of charge that can exist, right? Therefore, positron is all that too only with positive charge, yes? Are there some quarks, or whatever particles, that have smaller amount of charge than electron? If yes, then why are they not the 'elementary charges'? If not, then how do you know your quark is not actually an electron/positron? We can make a beam of electrons, can we make a beam of quarks? Can we observe quarks, or say muons, in bubble chamber? Charge is a property. An electron possesses elementary charge. It is not, itself, elementary charge. Muons and pions are trivially observed in bubble chambers. http://universe-review.ca/I15-02-bubblechamber.jpg http://www.particlephysics.ac.uk/news/picture-of-the-week/picture-archive/tracks-in-a-hydrogen-bubble-chamber.html Ok. How do we know (measure) photon has no mass? What is the value of photon momentum, for say red light? A zero mass is required by electrodynamics and relativity, and those theories work at very high levels of precision. There have been attempts to measure a mass, and they put very stringent limits on it http://silver.neep.wisc.edu/~lakes/mu.pdf http://www.aip.org/pnu/2003/split/625-2.html The momentum of a red photon is about 2.85e-19 kg-m/s Link to comment Share on other sites More sharing options...
Sha31 Posted December 11, 2009 Author Share Posted December 11, 2009 Right. It is the smallest charge that we can separate from a matter and operate with it - accelerate in accelerators, TV tubes, electronic lamps, etc. Quarks were invented (not directly observed) in order to: 1) explain some scattering experiments with heavy compound nuclei, 2) squeeze the quarks into a certain group of symmetry that require at the same time fractional charge of quarks (3 quarks in proton, neutron, and two in mesons) and impossibility to observe a quark in a free state. The strong interactions are so strong that one cannot separate things in a compound system without creating new coupled quarks. It is such a model in theoretical physics. Just keep in mind that strongly interacting things sometimes cannot be separated, like phonons from a solid. They are some quasi-particles - elementary excitations of compound systems. We can make proton beams that are beams of coupled together quarks. Quarks are always bound, mesons are well observed as free. Ok, thank you, that makes a lot of sense to me. Now, if I have a theory that all composite particles like protons and neutrons are actually made of assembles of positrons and electrons (elementary el. fields whose motion/spin causes magnetic fields), could you refute that? Link to comment Share on other sites More sharing options...
Mr Skeptic Posted December 11, 2009 Share Posted December 11, 2009 Electrons and positrons, when put together, will annihilate each other producing distinctive EM waves. How do you intend to keep them from annihilating? How will you explain the strong and weak nuclear forces with them? Link to comment Share on other sites More sharing options...
Sha31 Posted December 11, 2009 Author Share Posted December 11, 2009 (edited) Also an electron is made up of a quark and anti-quark: a Down quark and an Anti Up quark. The Down quark has a charge of -1/3 (e), where e is the charge of an electron (in absolute value) and the Anti Up quark has a charge of -2/3 (e), giving you -1 (e). If you can not observe these quarks separately, and their charge sums up to one electron, then how do you know that is actually not electron? But, electron is elementary particle, it is not made of anything, or so it would seem: http://en.wikipedia.org/wiki/Elementary_particle And P = E/c and E = hc/lambda, where lambda is the wavelength of the photon of light, so plug in the values and you will get the answer. Also, F = (k * Q*Q')/r^2 r and the electric field is F = Q E, so Q' does not mean its an electron or whatever, its the value of charge of the particle you are talking about. This is usually also for point like charges. So for the case of an electron it has a certain charge (e) you plug that in for the value of Q' and Q is the "test charge" at which you are looking at the electric field. What I'm trying to say is that electric field is no different thing from electron. Whenever you have some electron you can only know it's there indirectly by probing this electric field. You never actually observe and measure this "ball" we call 'electron' and is supposed to be in the center of this electric field. For all it matters we can take away what has NO SIZE and then we are still left with our field and its charge, we can call it 'electron', give it momentum (mass) and nothing has changed with experiments or equations. Unless, of course, there exist even smaller elementary amount of el. charge. Merged post follows: Consecutive posts mergedElectrons and positrons, when put together, will annihilate each other producing distinctive EM waves. How do you intend to keep them from annihilating? How will you explain the strong and weak nuclear forces with them? They do not really annihilate, they form photons (EM waves/radiation). This is confirmed by inverse process, "Pair production", which does the opposite - it splits this electric dipole (photon) into two monopole electric fields, positron and electron. http://en.wikipedia.org/wiki/Pair_production http://en.wikipedia.org/wiki/Pair_annihilation Superposition of positive and negative electric fields, neutralizing each other, would sure explain how can photons be made of electric fields and still have zero net charge, right? Electron and positron are trying to stick together, but due to their magnetic fields, instead of orbiting, they end up spiraling each other in some linear direction describing double helix, and there it is your transverse EM wave. http://en.wikipedia.org/wiki/Electromagnetic_radiation It's interesting Wikipedia even marks the graph with "+q" and "-q". I'm not aware of any effects of strong and weak nuclear forces with photons and EM waves. Merged post follows: Consecutive posts mergedCharge is a property. An electron possesses elementary charge. It is not, itself, elementary charge. Ok. Yes, I agree. I want to suggest that electric field is elementary entity and that electron, as elementary concept, is just an illustrative representation of this field, it's kind of the same thing. I say, fields can exist on itself (given the medium), like solitons, whirlpools and tornadoes that do not have some particle in the center of the field, but the whole dynamics of it acts as an entity itself. Muons and pions are trivially observed in bubble chambers. http://universe-review.ca/I15-02-bubblechamber.jpg http://www.particlephysics.ac.uk/news/picture-of-the-week/picture-archive/tracks-in-a-hydrogen-bubble-chamber.html Cool. Now, how do you know muon is not electron? According to that table above the only difference is in mass, but would not electrons with high enough frequency (energy) be indistinguishable from muon? In other words, what is the difference between mass given in electron volts and electron energy/frequency or kinetic/wave energy? How do you differentiate what is mass, what is energy and what is plain velocity? A zero mass is required by electrodynamics and relativity, and those theories work at very high levels of precision. There have been attempts to measure a mass, and they put very stringent limits on it http://silver.neep.wisc.edu/~lakes/mu.pdf http://www.aip.org/pnu/2003/split/625-2.html The momentum of a red photon is about 2.85e-19 kg-m/s According to p= m*v, mass of that photon is about: m= 2.85e-19 / c How much is (2.85e-19/c)kg in electron volts? Edited December 11, 2009 by Sha31 Consecutive posts merged. Link to comment Share on other sites More sharing options...
swansont Posted December 11, 2009 Share Posted December 11, 2009 Now, how do you know muon is not electron? According to that table above the only difference is in mass, but would not electrons with high enough frequency (energy) be indistinguishable from muon? In other words, what is the difference between mass given in electron volts and electron energy/frequency or kinetic/wave energy? How do you differentiate what is mass, what is energy and what is plain velocity? At low energy, energy scales with the square of the speed, i.e. KE = 1/2 mv^2, so speed and energy effects don't scale the same way. According to p= m*v, mass of that photon is about: m= 2.85e-19 / c How much is (2.85e-19/c)kg in electron volts? A red photon will have around 2 eV of energy (1240 nm will give you 1 eV), so the experimental limits exclude this by many frazillion standard deviations. Merged post follows: Consecutive posts mergedIf you can not observe these quarks separately, and their charge sums up to one electron, then how do you know that is actually not electron? But, electron is elementary particle, it is not made of anything, or so it would seem: Protons and neutrons are Baryons and behave/interact a certain way outside of electromagnetic interactions. Electrons are leptons, and behave differently. Link to comment Share on other sites More sharing options...
Sha31 Posted December 12, 2009 Author Share Posted December 12, 2009 A red photon will have around 2 eV of energy (1240 nm will give you 1 eV)' date=' so the experimental limits exclude this by many frazillion standard deviations. [/quote'] Thank you, I would have no idea how to even start converting that. Let me just note how that mass (energy) is right in the correct range of what would couple of electric fields have, like electron and positron. Now, we can have different energy photons, and IF we interpret mass in electron volts we could just as same say these oscillating electromagnetic fields (photons) actually increase in mass. But, we do know that in this case it is not mass that is increasing, we know it is the frequency/amplitude. In other words, it is the increase in some 'perpendicular velocity' or oscillation that brings in this extra energy - kinetic energy - momentum. Anyway, this logic, if correct, I want to apply to single electrons and see if we can indeed distinguish between electron kinetic energy (vibrations, oscillations, spin) and electron mass. At low energy' date=' energy scales with the square of the speed, i.e. KE = 1/2 mv^2, so speed and energy effects don't scale the same way. [/quote'] Ok. Can we have two electron beams with two different energies without changing the number of electrons emitted? In other words, can two electrons traveling a straight line, and having the same velocity, can they still have different energies due to some vibration, spin or something? Link to comment Share on other sites More sharing options...
Mr Skeptic Posted December 12, 2009 Share Posted December 12, 2009 Thank you, I would have no idea how to even start converting that. Well, the "for dummies" approach is to just put it into Google Calculator. Also works as the "for lazybums" approach. Link to comment Share on other sites More sharing options...
Sha31 Posted December 12, 2009 Author Share Posted December 12, 2009 Well, the "for dummies" approach is to just put it into Google Calculator. Also works as the "for lazybums" approach. That is not sufficient then. Can you explain how do you equate kg and eV? How come mass is expressed via some property of electric charge? What gravity field has to do with electric field and its kinetic energy, what is the relation? Link to comment Share on other sites More sharing options...
Mr Skeptic Posted December 12, 2009 Share Posted December 12, 2009 Hm, the thing is that all of these are units of energy. An electron-volt is the amount of energy an electron gains falling through 1 volt, and is particularly useful for particle accelerators, a Joule is what we use to measure the energy of normal sized objects, and mass is related to energy via Einstein's equation. Any of them can be used to measure energy, and people go with whichever is most convenient. Link to comment Share on other sites More sharing options...
Sha31 Posted December 12, 2009 Author Share Posted December 12, 2009 (edited) Hm, the thing is that all of these are units of energy. An electron-volt is the amount of energy an electron gains falling through 1 volt, and is particularly useful for particle accelerators, a Joule is what we use to measure the energy of normal sized objects, and mass is related to energy via Einstein's equation. Any of them can be used to measure energy, and people go with whichever is most convenient. Ok, but there is a problem. The definition is circular. Electron volt, the amount of energy an electron gains falling through 1 volt will depend on electron mass, hence this definition is unsuitable to be defining "mass" as it requires 'mass' to already be defined. Similar thing you can see with this equation for 'massless particles': p= E/c but... E= m*c*c ...so, again: p = m*c -> p = m*v Without mass energy is zero, without mass momentum is zero. Thus, if photons have energy and momentum they must have mass. Unfortunately, from all this it is still kind of unclear if 'mass' is a real property, do gravity fields really exist, or perhaps gravity force is just some side-effect due to motion of charges, effect of superposition of electric and magnetic fields and their kinematics/dynamics, their kinetic energy. But, anyhow, the real question is this: - can electrons traveling a straight line with the same velocity still have different energies due to some vibration, spin or something? Edited December 12, 2009 by Sha31 Link to comment Share on other sites More sharing options...
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