Electron and proton experiments

[unnamedxxx]

Hi folks,

 

I would like to know if there are experiments that show repulsive and/or attractive forces between electrons or protons. The structure of atom is not an example of such forces because the things there are more complicated. The interaction between two parallel electron and/or protons beams in high vacuum is such experiment, but I can not find it in the history of physics. /I googled for more than one week./ The force between current-carrying conductors is not an example because there are involved also the atoms of the conductor. Please be precise. I don't need explanations and theories, I need a real experiment.

 

Sorry for my bad english

[Daegurth]

proton-proton repulsion = Rutherford's famous gold foil/alpha particle experiment. here's a simple overview: Rutherford - Atomic Theory

 

if you prefer, electron-electron and proton-proton repulsion would both be covered by the gold leaf electroscope. it's static electricity based and demonstrates electron repulsion (when the stem/foil are negatively charged, full of extra electrons) and proton repulsion (when the stem/foil are stripped of electrons, leaving a net positive charge from atomic protons). basic overview: Gold leaf electroscope | Practical Physics

 

they both kinda involve atomic structure (the first a little more than kinda, since it changed the atomic structure paradigm), but they certainly clearly demonstrate the two repulsion types.

 

as for attraction, i can't think of one off-hand, but i'm sure there are plenty around. perhaps recombination of a hydrogen plasma?

[Qfwfq]

Coulomb scattering for intersecting beams? There are several journals which are choc full of experimental results back through the decades. If you don't have subscriptions to these journals you might need to go through some research library e. g. at a physics department.

 

Google

[CraigD]

Welcome to hypography, unnamed! :P

I would like to know if there are experiments that show repulsive and/or attractive forces between electrons or protons. ... I don't need explanations and theories, I need a real experiment.

Coulomb scattering for intersecting beams? There are several journals which are choc full of experimental results back through the decades. If you don't have subscriptions to these journals you might need to go through some research library e. g. at a physics department.

 

Google

Qfwfq’s suggestion seems best to me.

 

Since the electron beam equipment is cheap and common (every CRT has an electron gun and a detector screen), it’s tempting, if you’ve enough skill with high voltage electronics, vacuum pumps, and glassworking, to try your hand at an intersecting electron beams experiment. The physics fun part of this is calculating the expected scattering for practical beam speeds and density – without doing this, I’m not even sure there’d be enough effect to detect.

 

Props to anyone who does the calculating, and posts it here.

[unnamedxxx]

Thank you all for the answers to my question.

 

I have googled for "coulomb scattering for intersecting beams" but I haven't found any experimental data. I don't have subscriptions to such journals, so I am continuing my searches. I liked the idea to experiment with electron beams, but for now I don't have electron gun and high vacuum to test.

 

All I want is to check if the Coulomb's law is valid for elementary particles like electrons, and not a macro efect involving more than two electrons. It will be interesting to know if gravity also works on elementary particles like electrons. Maybe some of the forces are only effects on atoms and molecules.

[Qfwfq]

All I want is to check if the Coulomb's law is valid for elementary particles like electrons, and not a macro efect involving more than two electrons.

To check this in a purely empirical way would be a quite tricky task. There would be a substantial role of data analysis in any concievable method. At that point you might as well take hydrogen spectra as experimental data which fit the results of the models.

[CraigD]

All I want is to check if the Coulomb's law is valid for elementary particles like electrons, and not a macro efect involving more than two electrons.

Strictly speaking, any individual interaction involving very small (non macroscopic) particles won’t be well predicted by classical approximations such as Coulomb’s law, because, per quantum mechanics, they’re best described probabilistically. The precise momenta of a pair of electrons before and after exchanging an indeterminate number of virtual photons of magnetic interaction is not a pair of exact vectors, but a probability distribution of an infinite number of vectors.

 

However, if a large number of experiments involving pairs of interacting electrons are performed, the average of their momenta should agree with the classical approximation given by Coulomb’s law. Actually performing such experiments – using individual electrons rather than streams of large number of them – would, I think, be terribly difficult.

It will be interesting to know if gravity also works on elementary particles like electrons. Maybe some of the forces are only effects on atoms and molecules.

Measuring the effect of gravity on very small charged particles such as electrons is very, very difficult, because the relative strength of gravity is vastly smaller – about [imath]10^{-36}[/imath] times – than that of electromagnetism (see table in the overview section of the wikipedia article “fundamental interaction”). Since any practical lab is full of stray charged particles, I believe this renders directly testing the effect of gravity on electrons practically impossible.

 

An experiment to measure the effect of gravity on nearly the smallest neutral composite particles, hydrogen and antihydrogen atoms, should be in progress, or possibly complete. I discussed this last year in News from CERN: the upcoming AEGIS experiment.

[Qfwfq]

The precise momenta of a pair of electrons before and after exchanging an indeterminate number of virtual photons of magnetic interaction is not a pair of exact vectors, but a probability distribution of an infinite number of vectors.

Uhm, it isn't so much a problem of how many virtual photons. It can be related to the distribution of impact parameter via the Fourier-Bessel transform and hence seen as an eikonal and indeed the statistical analysis matches up very well with the [imath]\frac{1}{r}[imath] potential.

 

Actually performing such experiments – using individual electrons rather than streams of large number of them – would, I think, be terribly difficult.

It would be a matter of using intersecting beams of intensity such that most of the time there isn't more than one particle for each beam, in the collision zone. It would mean collecting data for a long time.

 

In the end it remains an indeirect observation, that's why I question whether it satisfies the query any more than hydrogen spectra.

[Rade]

Here is a paper that discusses electron <--> electron attractive gravitational force. Good place to look for possible experiments.

 

ScienceDirect - Physica C: Superconductivity : Gravitational force between two electrons in superconductors