Electric field, electric charge, electron and positron.

[Sha31]

Why a reference when you can see for yourself?

 

I'm asking questions' date=' stop being mysterious, be helpful, if you will. Where do I look? Are you referring to some equation? Reference because I want to learn the theory behind it and I want to know about experimental measurements that can confirm it. Can you now just answer the question without asking me any more questions, please. - What is the minimum electron velocity in low temperature superconductors?

[mp']Consecutive posts merged[/mp]

http://www.cfa.harvard.edu/itamp/slowelectrons.html#anchor636597 < many of the papers here deal with electrons with KE's of ~100eV

 

a tv will produce several keV electrons and particle colliders will provide GeV electrons.

 

this definitely indicates that they have an arbitrary speed.

 

I don't see mention of any velocities there. I want to know how to SLOW DOWN electrons, I want to read about electrons being brought to COMPLETE STOP.

 

The problem I have with TVs, accelerators and electron microscopes is that they do not actually measure any velocity, they assume they emit electrons at certain speed based on some voltage they supply to the instrument, but what is the experiment that actually measures electron VELOCITIES?

[insane_alien]

velocities aren't that useful. but kinetic energy is, so that is what is listed.

 

as it happens you get 5.93*10^6 m/sfor 100eV

 

a tv is up nearer 1.8*10^6m/s (assuming 1keV energies.)

 

with the paper swansont linked to you get 1741m/s

 

and particle accelerators and the like do emit narrow band velocities due to the way the plates and magnetic fields are arranged. electrons with significantly differing velocities get drawn off to the side or miss an appeture.

 

anyway, the velocities aren't typically useful in the energy ranges commonly dealt with. but expressing the kinetic energy of the electron in eV is. the energy is directly related to the velocity of the electrons.

[Mr Skeptic]

I'm asking questions, stop being mysterious, be helpful, if you will. Where do I look? Are you referring to some equation? Reference because I want to learn the theory behind it and I want to know about experimental measurements that can confirm it. Can you now just answer the question without asking me any more questions, please. - What is the minimum electron velocity in low temperature superconductors?

 

What makes you think I know? However, you can yourself calculate the average drift velocity of electrons in a superconductor. Simply find how many free electrons are in the superconductor (this can be found from how many electrons are free per unit of a superconductor and how many units are in a sample of superconductor (find this by the weight per unit and the weight of the sample). Multiply by the charge per electron and you get the total charge. Then for a current, you can calculate what portion of the charge is flowing through a section of the superconductor which will give you the average velocity of the electrons.

 

If you want to make a claim about the speed of electrons in a superconductor, you need some evidence not just complaining that no one is proving you wrong.

 

I don't see mention of any velocities there. I want to know how to SLOW DOWN electrons,

 

You were already told how. Did you find a mistake in my example?

 

Failure to show a flaw in my argument in post 70, or accept it, means I will no longer participate in your delusion.

[Sha31]

Physically why would you expect an "escape velocity" they are not classical orbits. It is knocked out of the bound state' date=' this takes energy. It is possible that it will be rebound later but immediately after it has been removed it is unbound.

 

http://hyperphysics.phy-astr.gsu.edu/HBASE/mod1.html#c5

[/quote']

 

According to my simulations they are in classical orbits actually, but in any case laws of electromagnetic attraction/repulsion apply. Your link actually confirms what I said. You see there are no "low velocities", low energy photons simply do not knock off any electrons, they do not transfer enough kinetic energy, i.e. VELOCITY, for electron to escape.

 

 

Not really magnetic poles, they are intrinsic spin angular momentum.

 

http://en.wikipedia.org/wiki/Spin_%28physics%29

 

There is no axis of rotation, hence intrinsic.

 

Yes, they are magnetic poles, north and south magnetic poles, whether you want to think they are caused by real spin or come built-in with each electron. But, I said I'm not talking about that spin, I'm talking about the other two axis perpendicular to the line connecting these two poles, like this:

 

 

Electron Speedometer

http://focus.aps.org/story/v17/st4

- "In a magnetic field, the spin axis of each electron rotates, or precesses, around the field, just as a tilted, spinning gyroscope or top precesses around the vertical gravitational field."

 

 

 

 

The two refernces I provide give KE which is related to velocity through a well known equation, as the KE goes to 0 as does the velocity.

 

I already know about equations and theories, now I want to know about experimental measurements and how exactly can we bring electrons to full stop? I want to know the average electron speed in superconductors and plasma.

 

 

Mr Skeptic, for simplicity I'm ignoring quantum effects and treating the electron as a classical particle, for the sake of the OP we need to get the easier physics understood first.

 

Please, don't ignore anything. Is <1>de Broglie frequency<1> actually describing <2>linear velocity<2>, or are these two variables independent and each can contribute to total electron energy by itself?

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What makes you think I know? However' date=' you can yourself calculate the average drift velocity of electrons in a superconductor. Simply find how many free electrons are in the superconductor (this can be found from how many electrons are free per unit of a superconductor and how many units are in a sample of superconductor (find this by the weight per unit and the weight of the sample). Multiply by the charge per electron and you get the total charge. Then for a current, you can calculate what portion of the charge is flowing through a section of the superconductor which will give you the average velocity of the electrons.

 

If you want to make a claim about the speed of electrons in a superconductor, you need some evidence not just complaining that no one is proving you wrong.

[/quote']

 

You have not provided any reference where I can learn how to do it, and I do not have experimental data to plug in whatever equation you're talking about. I'm asking question, you made a claim without evidence or any reference, but at least you admit now it was just an opinion.

 

 

 

You were already told how. Did you find a mistake in my example?

 

Failure to show a flaw in my argument in post 70, or accept it, means I will no longer participate in your delusion.

 

Argument? I'm not arguing, I'm asking for EVIDENCE. You failed to answer the question. I'm asking for REFERENCE, online ARTICLES and published PAPERS describing EXPERIMENTAL MEASUREMENTS. Good bye.

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velocities aren't that useful. but kinetic energy is, so that is what is listed.

 

as it happens you get 5.93*10^6 m/sfor 100eV

 

a tv is up nearer 1.8*10^6m/s (assuming 1keV energies.)

 

with the paper swansont linked to you get 1741m/s

 

and particle accelerators and the like do emit narrow band velocities due to the way the plates and magnetic fields are arranged. electrons with significantly differing velocities get drawn off to the side or miss an appeture.

 

anyway, the velocities aren't typically useful in the energy ranges commonly dealt with. but expressing the kinetic energy of the electron in eV is. the energy is directly related to the velocity of the electrons.

 

Ok, thanks. That's what I want - numbers. Now, what I'm looking for is some experiment that measures the speed of electrons based on velocity= distance/time, instead of based on momentum.

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In case you missed the earlier post about electrons in a Penning trap' date=' though,

 

[indent']The trap and the electron's cyclotron motion are cooled to about 100 milliKelvin[/indent]

 

What is the velocity of that electron? How is that velocity measured/calculated?

Edited December 16, 2009 by Sha31
Consecutive posts merged.

[Cap'n Refsmmat]

This discussion is getting a little too uncivil for my tastes. Could we please stay civil? Heated discussion just makes this less productive.

[Sha31]

Well' date=' that seems interesting, but remember that your ideas have to account for the real world. And remember that electromagnetic fields can be blocked, and can repel as well as attract. So you need to find a way to make your thing behave like gravity.

[/quote']

 

I did not mean to say gravity force is some product of superposition of magnetic and electric forces. I agree there are three kinds of fields and three forces: electric, magnetic and gravitational. What I'm trying to say is that there is no such thing as 'mass', and that all energy is kinetics, including "mass". There is gravity field, yes, but it's magnitude does not increase with some surplus of "matter", rather it's caused by the dynamics of it, just like with photons.

Edited December 17, 2009 by Sha31

[npts2020]

Sha31; When you googled experiments/electron speed, what did the first half dozen or so sites have to say? The problem with bringing an electron to some "state of rest" is that it is a charged particle and will be attracted to everything around it and therefore want to move from any resting state. You have asked several people here for proof, sometimes even after it was provided but have shown no proof yourself for there being any cause to disbelieve the reasons given for being able to vary the speed of an electron.

[Sha31]

Sha31; When you googled experiments/electron speed' date=' what did the first half dozen or so sites have to say?

[/quote']

 

I searched much more than that and I gave you the best link I could find - "Electron Speedometer". If you are some 'googling guru', then please do find at least one link which talks about experimental measurements of electron velocities in vacuum, superconductors or plasma.

 

 

The problem with bringing an electron to some "state of rest" is that it is a charged particle and will be attracted to everything around it and therefore want to move from any resting state.

 

Not really, the environment is largely magnetically and electrically neutral. Perhaps you are talking about the difficulties of assembling uniform electromagnetic fields to capture electrons and Earnshaw's theorem?

 

 

You have asked several people here for proof, sometimes even after it was provided but have shown no proof yourself for there being any cause to disbelieve the reasons given for being able to vary the speed of an electron.

 

I'm not disbelieving anything since I have not seen anything yet. I simply want to learn about relevant experiments. My reason to question is based on the lack of evidence, that's all. I'm talking about velocities like 100-0 m/s. Are you comfortable with photons not being able to slow down?

Edited December 17, 2009 by Sha31

[swansont]

I'm not disbelieving anything since I have not seen anything yet. I simply want to learn about relevant experiments. My reason to question is based on the lack of evidence, that's all. I'm talking about velocities like 100-0 m/s. Are you comfortable with photons not being able to slow down?

 

If measuring a specific electron's speed isn't interesting to scientists, they aren't going to do an experiment. What would this experiment show, and why is that a reasonable way to use up finite lab resources? It's quite possible the specific experiment you describe has not been done.

 

Physicists have models of how things work, and these are extensively tested. A thermal collection of particles will always have slow-moving particles in it. This is well-established physics. Further, if an electron backscatters, it must accelerate and sample speeds down to zero as it changes direction, just like a ball tossed in the air will be momentarily at rest at the apex of its trajectory. This is first-semester physics.

 

Conclusion: Electrons can have arbitrarily small speeds.

 

 

———

 

I think there is a bit of frustration here, because on the one hand you are demanding evidence based on an argument from incredulity (exacerbated by apparently not knowing much physics), and yet you are proposing a model, namely there is no such thing as 'mass', and that all energy is kinetics, including "mass", and yet you have complained — multiple times — about questions being asked of you. You're asking people to be helpful, but you will not do them the courtesy of learning some of the basic material you need to know to understand the details of the discussion.

[Sha31]

Dear swansont,

 

I have 7 years of university education, physics and computer science, as well as 18 years of experience in experimental physics and manufacturing, actually working in a laboratory. I could just the same tell how you do not understand and have no idea what are you talking about, but that's lousy argument, so if you'd like to disagree with some statement, which is not my question, then just bring on the arguments and stop waving hands.

 

 

If measuring a specific electron's speed isn't interesting to scientists, they aren't going to do an experiment. What would this experiment show, and why is that a reasonable way to use up finite lab resources? It's quite possible the specific experiment you describe has not been done.

 

Physicists have models of how things work, and these are extensively tested. A thermal collection of particles will always have slow-moving particles in it. This is well-established physics. Further, if an electron backscatters, it must accelerate and sample speeds down to zero as it changes direction, just like a ball tossed in the air will be momentarily at rest at the apex of its trajectory. This is first-semester physics.

 

Conclusion: Electrons can have arbitrarily small speeds.

 

Real physicists should be very interested to know things like this, it would help them keep electrons in one location, help them take more precise measurements... and disprove QM in the same time. -- Anyhow, I'm asking very specific question: about linear velocity of FREE electrons in vacuum, superconductors and plasma. Do you know anything about this? "arbitrarily" (usually) means 'according to human decision', on purpose, at will. So, what you need to show is some experiment that can slow down electrons to around zero velocity. Do you know anything about this?

Edited December 17, 2009 by Sha31

[Cap'n Refsmmat]

http://en.wikipedia.org/wiki/Penning_trap

[swansont]

Dear swansont,

 

I have 7 years of university education, physics and computer science, as well as 18 years of experience in experimental physics and manufacturing, actually working in a laboratory. I could just the same tell how you do not understand and have no idea what are you talking about, but that's lousy argument, so if you'd like to disagree with some statement, which is not my question, then just bring on the arguments and stop waving hands.

 

I have a very hard time reconciling this with (and this is not an exhaustive observation) your seeming inability to distinguish between a charge and its field, your requests for others to do simple equation manipulations, unfamiliarity with relativity and more basic physics concepts, inability to carry units through an equation and do unit substitution.

 

Something does not add up here.

 

 

Real physicists should be very interested to know things like this, it would help them keep electrons in one location, help them take more precise measurements... and disprove QM in the same time. -- Anyhow, I'm asking very specific question: about linear velocity of FREE electrons in vacuum, superconductors and plasma. Do you know anything about this? "arbitrarily" (usually) means 'according to human decision', on purpose, at will. So, what you need to show is some experiment that can slow down electrons to around zero velocity. Do you know anything about this?

 

 

I've mentioned thermal velocity distributions a number of times. Do you know anything about this? If you have the resumé (or vita) that you claim, you should be well aware that electrons can have small speeds.

 

I can think of a number of reasons why a physicist would not be interested in spending his or her research dollars on an experiment like this, whose goal is disproving quantum mechanics. The overwhelming weight of evidence that QM is correct is one, and that a fool's-errand failed experiment is not a good way to attract further research funding is another.

[Klaynos]

According to my simulations they are in classical orbits actually, but in any case laws of electromagnetic attraction/repulsion apply.

 

OK, I think we need to pause for a moment here. How do you get around the fact you have accelerating (and thus emitting) charges, they would be loosing energy at a phenomenal rate!

 

There is a staggering amount of evidence for electron orbitals, NOT orbits.

 

Your link actually confirms what I said. You see there are no "low velocities", low energy photons simply do not knock off any electrons,

 

There is a threshold, if you have the physics background you claim you should be well aware of the photoelectric effect.

 

they do not transfer enough kinetic energy, i.e. VELOCITY, for electron to escape.

 

The energy of an escaped electron is the absorbed energy - the binding energy, the left over energy goes into KE, if there is none there is no velocity.

 

Yes, they are magnetic poles, north and south magnetic poles, whether you want to think they are caused by real spin or come built-in with each electron.

 

I'm afraid you are just wrong here, it is well known and demonstrated by many experiments that electron spin is intrinsic.

 

But, I said I'm not talking about that spin, I'm talking about the other two axis perpendicular to the line connecting these two poles, like this:

 

 

Electron Speedometer

http://focus.aps.org/story/v17/st4

- "In a magnetic field, the spin axis of each electron rotates, or precesses, around the field, just as a tilted, spinning gyroscope or top precesses around the vertical gravitational field."

 

 

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000096000003037601000001&idtype=cvips&gifs=yes

 

Is a better science reference. You might like to note that their drift velocity goes through 0.

 

I already know about equations and theories, now I want to know about experimental measurements and how exactly can we bring electrons to full stop? I want to know the average electron speed in superconductors and plasma.

 

They you know that if you reverse an accelerating field you get an acceleration in the other direction meaning you can trivially slow down and reverse electron beams.

[mooeypoo]

Seeing as this isn't mainstream science, and deals with a speculative matter, the thread is moved to speculation forum.

[Sha31]

http://en.wikipedia.org/wiki/Penning_trap

 

What is electron velocity?

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I've mentioned thermal velocity distributions a number of times. Do you know anything about this?

 

Yes' date=' I know. What I don't know are electron velocities in those distributions and how it was measured. Do you know anything about that?

 

 

If you have the resumé (or vita) that you claim, you should be well aware that electrons can have small speeds.

 

Can we bring electrons to full stop?

 

No, I'm not aware. I'm not even aware of any experimental measurements of electron speed. I'm interested in numbers, in technology used to slow down electrons or measure velocities. Are you aware? Can you provide some reference to some actual numbers?

 

 

The trap and the electron's cyclotron motion are cooled to about 100 milliKelvin

 

What is the velocity of that electron?

How is that velocity measured/calculated?

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OK' date=' I think we need to pause for a moment here. How do you get around the fact you have accelerating (and thus emitting) charges, they would be loosing energy at a phenomenal rate!

 

There is a staggering amount of evidence for electron orbitals, NOT orbits.

[/quote']

 

No problem, we can pause, after you provide some evidence for the original question:

 

You can have an electron from 0m/s to infinitely close to (but not at) the speed of light in a vacuum.

 

Can you provide some evidence for that?

 

 

 

There is a threshold' date=' if you have the physics background you claim you should be well aware of the photoelectric effect.

[/quote']

 

Threshold, yes, which is what I predicted.

 

Klaynos: -"When you remove an electron from an orbital shell, if the work energy is say 3Energy units, and you give it 3.5Energy units the electron will have .5Energy units of KE, but if you give it 3Energy units the electron will become removed from the atom and have 0Energy units of KE, meaning it cannot be moving."

 

So, do we now agree you were wrong when you said this or can you support that claim with some evidence?

 

 

 

I'm afraid you are just wrong here, it is well known and demonstrated by many experiments that electron spin is intrinsic.

 

Wh..?? Wrong about what?

Do you mean to say that article is wrong?

 

 

1.) Every electron has dipole moment - two magnetic fields, yes/no?

 

2.) Can this axis (line passing through N/S poles) change orientation, yes/no?

Edited December 17, 2009 by Sha31
Consecutive posts merged.

[swansont]

Yes, I know. What I don't know are electron velocities in those distributions and how it was measured. Do you know anything about that?

 

If you are aware of the distributions, how can you not be aware that they are number vs speed, so you can determine the fraction of particles in a velocity range?

 

 

Can we bring electrons to full stop?

 

Within the limits of the Heisenberg Uncertainty principle, yes.

 

 

Threshold, yes, which is what I predicted.

 

Klaynos: -"When you remove an electron from an orbital shell, if the work energy is say 3Energy units, and you give it 3.5Energy units the electron will have .5Energy units of KE, but if you give it 3Energy units the electron will become removed from the atom and have 0Energy units of KE, meaning it cannot be moving."

 

So, do we now agree you were wrong when you said this or can you support that claim with some evidence?

 

Klaynos was not wrong. If you think he is, you need to go back over what he wrote.

 

If you add the ionization energy to an atom, and no more, the electron will have no energy left over.

 

———

 

Can you provide some evidence for that?

 

You have been provided evidence, some of which is in the form of a well-established theory.

 

If a rock is one day seen at the top of a hill, and the next day found at the bottom, how did it get there? We say it was due to gravity, even though nobody witnessed it. because we have a well-established theory. Similarly, the physics behind motion and thermodynamics is well-established. To the extent that classical physics can be applied to the problem, a collection of electrons in thermal equilibrium will have some at low speeds and that electrons being deflected or scattered will have their speeds become small.

 

You have also been pointed toward trapping and cooling techniques that demonstrate that we can manipulate individual electrons.

 

Why are you refusing to accept this as evidence?

[Sha31]

Ok, thank you for your input.

I like the bit about stone on a hill.

 

 

 

Can someone provide links to articles or papers describing velocities of FREE electrons in vacuum, superconductors or plasma?

 

Can someone provide links to articles or papers describing how exactly can we 'slow down' free electrons, what technology is used, and what is the MINIMUM velocity achieved?

[moth]

maybe you could check out CRT technology.

here's a link to a reference with lots of equations from a wikipedia article on CRT

http://wps.aw.com/wps/media/objects/877/898586/topics/topic07.pdf

 

i'm not too good with the math but i think the deflection fields would need to be much stronger if the electrons only travel at c.