Tagged Questions

Negatively charged particle with spin 1/2. A component of mundane terrestrial matter, and part of all neutral atoms and molecules. It has a mass about 1/1800 that of a proton. Its antiparticle is the positron.

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Why are pernament magnets pernament?

If I get it right when iron bar is attracted by pernament magnet it becomes the magnet itself because all of its magnetic domains starts to point in the same direction. When iron bar is no longer ...
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0answers
14 views

Can we calculate L-S coupling without Dirac equation?

It is known that there exists an orbital and spin angular momentum coupling for an electron moving in the atom. And the Hamiltonian can be directly derived using Dirac equation. I want to use a ...
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0answers
22 views

Why free electron has orbital magnetic moment?

I was about to ask why don't we use electron beam instead of atoms in Stern-Gerlach experiment, then I saw this question and my question become why free electron has orbital magnetic moment...
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3answers
168 views

How is a photon measured?

If photons transmit the electromagnetic force, which is observable: the photon or the electron? Do we ever directly measure a photon, or do we only measure it's effect on electrons. For example ...
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3answers
85 views

Self-energy of electron from classical reasoning

If it takes energy to group charge together(self energy) how can it be possible for every single electrons, etc, to have exactly same amount of charge? (think of if we hold some sand in our hand, then ...
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0answers
21 views

Question on calculating the number density of free electrons in the sun's photosphere

I am writing a paper on the effect H$^-$ (a hydrogen atom with an additional electron) has on the opacity in the sun's photosphere. As such, I need to calculate its abundance. Doing so is ...
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1answer
26 views

How can nuclear decay both annihilate and create?

This'll be back to basics for many of you, but here's something I still don't get. How can nuclear decay of an unstable atom both create and annihilate positron-electron pairs? You have an unstable ...
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2answers
53 views

Charged particle singularity

Is it possible to manipulate magnetic/electric fields, similar to magnetic confinement technologies/penning traps, to compress charged particles into black holes?
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1answer
58 views

The “classical radius” of the electron [closed]

According to one theory, the mass m of the electron arises simply as a consequence of the electrostatic energy of its electric field, through Einstein's famous expression ε=mc^2, where ε is the field ...
8
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1answer
107 views

If protons and electrons had similar masses

If electrons and protons had the same mass, would they still be in a stable orbit around their barycenter, or would they eventually collide? Similarly, a positronium(or protonium) only lasts extremely ...
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2answers
47 views

Is it possible for electrons to carry more than one charge?

Sorry if this has been asked before. Could also be a really basic question (new to electrical study). I am a bit confused about the relationship between electrons and charges. So what I understand is ...
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0answers
32 views

Charge density within radius r from the nucleus

The probability of finding an electron within radius $r_b$ for Hydrogen near the center ($r_b<< a_0$) is approximately equal to zero (according to 1s orbital curve). Does this imply that the ...
19
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2answers
2k views

Why don't free electrons fall from metals if shaken?

This is a question we were asked at a physics lecture.
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4answers
75 views

Can neutrons be synthesized purely from protons and electrons?

Can neutrons be synthesized purely from protons and electrons? Note: I'm looking for reactions that do not require neutrinos or any particles besides just protons and/or electrons as reactants.
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1answer
27 views

Why in PN junctions the octet rule is dominating electrostatic repulsion?

The depletion region in PN junctions is created by charges from the N part diffusing into the P part, thus completing an octet of covalent bonds in the P part. This shift however leaves positive ions ...
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0answers
38 views

Photoelectric effect Experiment - What's the voltage bias of the set up?

What's the bias of the setup? Forward / Reverse? I'm doing a photoelectric effect experiment.The experimental setup involves a photocell, which has an emitter (cathode) Potassium and a ...
0
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1answer
18 views

Foucault currents with a simple pendulum

I have this diagram : It's a kind of pendulum; when it swings, it passes through a small aera where there is a magnetic field. Therefore, the electrons moves towards the bottom because of a Lorentz ...
0
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1answer
46 views

Question about one of the problems of the Bohr model

This is probably extremely basic physics that I don't know, but I'm still going to ask: Say in hydrogen, according to the Bohr model the electron is "really" orbiting the proton, and as a consequence ...
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1answer
140 views

Can an electron stand in place of proton like a ghost standing in place of you?

The atomic orbital refers to the physical region where the electron can be calculated to be present, as defined by the particular mathematical form of the orbital 1. The picture below shows the $1s$ ...
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7answers
2k views

Does electron being many places at the same time violate Physics laws?

The following passage has been extracted from the book Parallel Worlds, by Michio Kaku: Because of uncertainty, the electron does not exist at any single point, but exists in all possible ...
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1answer
74 views

What makes electrons lose energy?

As far as I know from physics lessons I got at school, electrons go up to higher energy levels when they capture a photon. But, once an electron is at a given level, what makes it go down to a lower ...
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0answers
56 views

What is the difference between photoelectric effect and Compton scattering?

What is the difference between photoelectric effect and Compton scattering? These two effects explains interaction of photon with electron. Why in photoelectric effect whole energy of photon is used ...
0
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1answer
33 views

Kinetic energy of an electron in synchrotron

The question states as follows: An electron is accelerated in a LINAC (LINear Accelerator) so that it's kinetic energy is 1.00 GeV. Then it is transferred to a synchrotron where it's energy (didn't ...
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2answers
91 views

What does volume means at the quantum level?

The volume of the electron is the space bounds in which it is contained says the @CuriousOne. But how can we define the volume in such a small range. If we immerse a cuboid into a vessel full of ...
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0answers
39 views

Does an electron occupy a definite volume? [duplicate]

The proton is about 1.6–1.7 fm in diameter. Quoted from Wikipedia. That is,The proton just occupies a definite volume or a definite space. But I can't find the radius of an electron in ...
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2answers
30 views

In low voltage (3-12V) DC applications, which is safer to be exposed or touchable + or - terminal?

The - side has a surplus of $e^{-}$s and the opposite is true for the + side of the power supply. Does it not matter, or depends on your configuration / contact with Earth? Please explain!
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1answer
36 views

Drift velocity of electrons with changing area

What would happen with the drift velocity of a cylindrical resistor's diameter increases, with a given voltage between its terminals? According to the expression: \begin{align} ...
3
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2answers
82 views

If stars are ionized, where are the electrons?

As far as I know, universe is electrically neutral so, If stars are ionized, where are the electrons?
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2answers
52 views

What is the speed of an electric spark/arc in vacuum?

I am just curious about the nature of an electric spark, how fast are the electrons moving? Will these electrons slow down when the spark occurs through a dielectric? (e.g., air)
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0answers
36 views

Are the electric charges of an electron and a proton equal or approximately equal? [duplicate]

I read in Auletta's quantum mechanics (section 11.2) that the charge of the proton is, apart from the sign, approximately equal to that of the electron.. What ...
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2answers
42 views

What causes the random movement of particles inside a conductor?

I'm reading about currents in electricity right now, and it was mentioned that even if there's no electric field inside a conductor, charged particles inside are still undergoing random movement. I ...
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0answers
22 views

Doppler effect for the electrons emitted from ions moving at a particular velocity

If I have ions moving in X axis (along both directions; positive X axis and negative X axis) and if I irradiate laser along the positive X axis, electron will be ejected from the ions (if I am using a ...
2
votes
1answer
30 views

Reconciling electron subshell configurations and the Pauli exlcusion principle

I'd like to prefix this with an apology: I have no formal training in QP, and most of what I know has been obtained by reading Wikipedia. As such, it'd be really helpful if any answers took my lack of ...
2
votes
3answers
64 views

Electron flow in a wire [duplicate]

How do electrons that constitute a current flow move in a wire? Some say it's like a wheel.If you give it a push,every part of the wheel moves instantly. Is that what happens to electrons?Do they ...
16
votes
4answers
2k views

Can two electrons get ever so close as to touch each other?

My friend and I were studying for our EM test when we started to think about what happens to the electric field near an infinite line of charge. $$E = \frac{\lambda}{2\pi\rho\epsilon_{0}}$$ As you ...
2
votes
1answer
36 views

Thermal emission cathode electron velocity distribution

I can't find any experimental data (or theoretical expression) on what is the velocity (or energy) distribution of thermal emission cathode electrons emmited from the cathode at approximately 2000 K ...
1
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0answers
32 views

Momentum of electron problem [duplicate]

Recently, my friend bemused me with a question related to the momentum of an electron. The confusing logic is stated below: Since an electron is a particle and according to classical physics, we know ...
1
vote
1answer
36 views

How does velocity relate to energy difference in Compton scattering?

I'm having trouble understanding what my professor is getting at asking in this question. I just visited her office and her explanation minutely helped. I'm hoping to get a bit more clarity on what is ...
8
votes
2answers
1k views

How does an electron move around in an orbital? Is it “wave-like” or random?

When an electron is moving around in it's orbital, is it actually moving around like a wave, like this video shows? (By wave-like, I mean, the "electron" in this video is showing it following a ...
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0answers
13 views

Difference between free electron and the electron in potential well [duplicate]

Is there any difference between free electrons and the electrons in potential well? Is there any energy difference between those two?
7
votes
2answers
125 views

Stable muon density inside a white dwarf star?

It occurs to me (though I'm hardly the first) that the decay $$ \mu^- \to e^- + \bar \nu_e + \nu_\mu $$ should be forbidden in electron-degenerate matter, since there must be an empty state available ...
4
votes
1answer
64 views

Only transverse photons are gauge-invariant (Peskin page 298)

Seven lines down from the top of page 298 of P & S, it says "Single particle states containing one electron, one positron, or one transversely polarized photon are gauge-invariant, while states ...
2
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4answers
205 views

How did photons and electrons arise out of the quark-gluon plasma?

I am just beginning to learn about the ideas of the early universe, so this is probably a beginner question. I understand that protons and neutrons (which are baryons, which are hadrons) are made out ...
2
votes
3answers
252 views

Why can't electrons fall into the nucleus?

I read a book on pop sci book on quantum mechanics and the author said that electrons do not fall into the nucleus due to quantum mechanics- which principles suggest this (I think it was Heisenberg's ...
0
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2answers
57 views

How hot particles can get [duplicate]

One way in which an object is affected by temperature rise is that the wavelength of the radiation it emits is gets smaller and smaller. Another way of looking at it is that as an object gets hotter, ...
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0answers
31 views

Recombination time for ionized atoms in a low pressure gas?

I am looking into some new physics and had the following question come up: You have a neutral gas of let's say, CO atoms at 1 nanoTorr. An electron(s) comes passing through the gas ionizing only 1% ...
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2answers
62 views

Is the electron magnetic moment responsible for the Lorentz force?

My question about the sum of the electrons' magnetic moments in a wire(What is the sum of the electrons' magnetic moments in a wire?) had an answer which disappeared later. The answer was - if I ...
1
vote
1answer
53 views

What is the sum of the electrons' magnetic moments in a wire?

The electron has a magnetic moment. This magnetic moment will be influenced in a electric field; the magnetic moments will be more or less aligned. During the movement of an electron in a wire under ...
4
votes
1answer
125 views

Electron Charge is 150%?

Is there a theory for why the charge of an electron is precisely 50% larger (magnitude) than a quark's? I have usually thought of this the other way around: the charge of a quark being 2/3 (or -2/3) ...
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2answers
273 views

What is the spin of an electron along the x-axis?

I know that an electron or any other particle for that matter, has a measured spin which is either up or down. This spin is along the z-axis. But what if we do not measure it along the z-axis and do ...