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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Stability of a rotating ring of multiple electrons at relativistic speeds

There was a time when physicists where concerned about electron internal structure. The rotating ring model was one of the proposals to explain how a charge density could become stable against ...
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can I move the atom core only?

I was wondering if it is possible to move the atom core and leave behind the electrons. I can imagine that the electrons will follow the core. But what if the speed of the core is almost the same as ...
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What does $\psi_j(r_i)$ mean?

I have a mean-field Hamiltonian for N electrons. The mean-field potential felt by electron $i$ at position ${\bf r}_i$ is given by $V^{(i)}_{int}({\bf r}_i)=\sum_{j\ne i}|\psi_j({\bf r}_i)|^2$ I ...
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Excess charge on an insulator and conductor

So I was recently wondering what happens to the excess charge when it is placed on an insulator or conductor e.g. rubbing two objects together. I know in the conductor the electrons are free to move ...
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Units in cgs system

How do I find the dimensions of this quantity (in $cgs$)... $$\frac{4\pi me^2}{h^2n_o^{1/3}}$$ where $m$ is the mass of electron $e$ is the magnitude of electronic charge $h$ ...
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Is Fractional quantum Hall effect proof that leptons are composite particles?

The fractional quantum Hall effect (FQHE) is a physical phenomenon in which the Hall conductance of 2D electrons shows precisely quantised plateaus at fractional values. Should this be considered ...
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Why is the anode (+) in a device that consumes power & (-) in one that provides power?

I was trying to figure out the flow of electrons in a battery connected to a circuit. Conventionally, current is from the (+) terminal to the (-) terminal of the battery. Realistically it flows the ...
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Making or Demonstrating Principle of Electron Microscope

is it possible to either demonstrate the principle or make a SEM ( electron microscope ) at home or lab as an enthusiast?? and how can i start?
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The electron jumps and lets loose photons

Where is the source of the photon. If the photon propagates from within the electrons transit does this point to some sort of field? Does the energy come from a boundary being broken in laymens ...
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Why do electron-positron pair annihilate upon contact?

I'll a appreciate a layman's explanation, if there exists one, to this question that arose when reading an popular-science level article on Einstein and the $E=MC^2$ equation. What I mean is that, ...
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Why do electron and proton have the same but opposite electric charge?

What is the explanation between equality of proton and electron charges (up to a sign)? This is connected to the gauge invariance and renormalization of charge is connected to the renormalization of ...
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Why is it that protons and electrons have exactly the same but opposite charge? [duplicate]

Possible Duplicate: Why do electron and proton have the same but opposite electric charge? Doesn't it seem very curious that one is an elementary particle and the other a subatomic particle ...
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Bohr's model of an atom doesn't seem to have overcome the drawback of Rutherford's model

We, as high school students have been taught that-because Bohr's model of an atom assigns specific orbits for electrons-that it is better than Rutherford's model. But what Rutherford failed to explain ...
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Why do electrons make a Fermi sphere?

In Sommerfeld theory for metals, after determining all of the possible levels for a single electron, one says that we build up a state for a system with $N$ electrons by filling up those levels, ...
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why is total electron energy of an electron in metal negative?

In my textbook, it says that any electron bound in metals, modelled as some potential well $U$, has negative total electron energy, as shown below in the figure. Why is the total electron energy ...
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How do electrons know that?

The current is maximum through those segments of a circuit that offer the least resistance. But how do electrons know beforehand that which path will resist their drift the least?
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A basic confusion about what is an atom

Wikipedia defines atom as The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. and defines electron as: The ...
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True or false? Particle physics [closed]

It is not possible to prove the point of origin of a photon It is not possible to prove the point of origin of a free electron It is not possible to prove that protons or neutrons exist inside a ...
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fit funtion to the Sun electron fluxes data

I'd like to fit a function to the Sun's electrons flux data (blue dots), please note that x,y axis are in the log scale. The green dots are the "best" fit from the gnuplot program. I have taken the ...
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Why do electrons around nucleus radiate light according to classical physics

As I navigate through physics stackexchange, I noticed Electron model under Maxwell's theory. Electrons radiate light when revolving around nucleus? Why is it so obvious? Note that I do not know ...
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Is there a list of all atomic electron state transitions and the corresponding radiation emitted?

Here's a quote from Wikipedia: As an example, the ground state configuration of the sodium atom is 1s22s22p63s, as deduced from the Aufbau principle (see below). The first excited state is ...
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Will an entangled idler electron induce a current in a conductor if the signal elctron's spin is measured?

I'm assuming a hypothetical setup as follows: Two labs (Alice and Bob) exist. Each has one electron of an entangled pair. At Alice, the electron travels through free space towards a magnetic field of ...
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How important are electromagnetic tidal effects in QFT? Can they be used to determine whether a particle is point-like?

I just did a back-of-the-envelope calculation, which surprised me. I calculated the difference in acceleration (due to repelling like-charges) experienced by two sides of an electron the size of the ...
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Can I get anions by touching the negative electrode of a battery?

It is said that anions are good for health. Instead of using an anion generator, can I get anions by touching the negative electrode of a battery?
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Is there a point interaction model of the electron?

Is there a point interaction model of the electron? Is there a point interaction model of the electron? I imagine something like $\propto(\bar \psi\psi)^2$ (edited). Is such a thing in use? Since I ...
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What happens to the absorbed light energy?

When light comes across with a solid material, some of it is reflected, some of it passes through and some of it is absorbed. I understand the reflection and passing through, but I don't understand ...
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How can one describe electron motion around hydrogen atom?

I remember from introductory Quantum Mechanics, that hydrogen atom is one of those systems that we can solve without too much ( embarrassing ) approximations. After a number of postulates, QM ...
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How to know what materials are good conductors of electricity?

I'm not asking a question like "Is the wood conductive?". No. I'm asking what properties do they have to have to be good conductors. Theoretically I mean. Thanks.
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Do Positrons Bend The Same Direction As Electrons In A Magnetic Field?

Electrons obey the right hand rule when a magnetic field bends their path. According to the right-hand rule, will positrons bend in the same direction?
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Electron Positron annihilation Feynman Diagram

I am having some trouble understanding this fenyman diagram, it seems to indicate that the electron produces the positron, as the arrow of the positron is pointing from the electron. Additionally ...
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Do “shape” and “volume” in “space” have any meaning for an electron?

The Standard Model (SM) predicts an "aspherical" electron due to its possesing a non-zero electron electric dipole moment (EEDM). An experiment by Hinds (2011) placed an upper bound on the ...
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Definition of Free Electrons and Mobile Charges?

Could someone please give me a good definition of the following electric terms? Despite what searching I have done, I have not come across a definition that I have found clear for me to understand: ...
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How would Kohn-Sham orbitals differ from 'true' elecron wavefunctions?

How would the non-interacting electron orbitals from a perfect DFT solution for a given potential shape differ from the 'true' electron wavefunctions? Or can you only really talk about the total ...
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Is the free electron wavefunction stable?

The wavefunction of a free electrons is variously described as a plane wave or a wave packet. I am fairly happy with the wave packet, as it is localised. But if we change to the electron's rest ...
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What are the specific electronic properties that make an atom ferromagnetic versus simply paramagnetic?

As I understand it, paramagnetism is similar in its short-term effect to ferromagnetism (spins of the electrons line up with the magnetic field, etc.), though apparently the effect is weaker. What is ...
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Electrons - What is Waving?

If an electron is a wave, what is waving? So many answers on the internet say "the probability that a particle will be at a particular location"... so... the electron is a physical manifestation of ...
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Thought experiment with entangled electrons

Suppose we start out by having two entangled electrons. We separate them by some distance and we put one electron inside a thin loop of wire connected to an extremely sensitive voltage measuring ...
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Oil drop experiment--How was the result so accurate?

I remember while learning about Millikan's oil drop experiment and being pretty skeptical about the setup. I know that there is a lot of controversy regarding manipulation of data, but the fact is; he ...
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Current in a simple circuit

I was going over my notes for an introductory course to electricity and magnetism and was intrigued by something I don't have an answer to. I remember my professor mentioning, to the best I can ...
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Why is the value of spin +/- 1/2?

I understand how spin is defined in analogy with orbital angular momentum. But why must electron spin have magnetic quantum numbers $m_s=\pm \frac{1}{2}$ ? Sure, it has to have two values in ...
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If an atom is fully ionized by removing all electrons, is it still an atom?

This is a question about terminology. To me, it's clear that the nucleus of an atom is still an atom. But a comment by Willie Wong at Is nature symmetric between particles and antiparticles? raises ...
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What was missing in Dirac's argument to come up with the modern interpretation of the positron?

When Dirac found his equation for the electron $(-i\gamma^\mu\partial_\mu+m)\psi=0$ he famously discovered that it had negative energy solutions. In order to solve the problem of the stability of the ...
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Are energies non-transferable in the Born-Oppenheimer approximation, and when does it apply?

Adiabatic approximation or the Born-Oppenheimer approximation is used whenever the electronic motion is too fast that the electrons effectively see static nuclei and the nuclei, in turn, see an ...
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Electron behavior changes when observed?

I saw this video of the double slit experiment by Dr. Quantum on youtube. Later in the video he says, the behavior of the electrons changes to produce double bars effect as if it knows that it is ...
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Small confusion related to leaving of electrons from atoms

Picking up a circuit board from a table, or our clothing rubbing as we walk, sit and work, are all examples of movement that can create static charge. One object, or surface, picks up additional ...
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How does thermal broadening of the Fermi Function cause electron coherence loss?

Generally, there are two ways for electrons to lose their wave-like properties in a solid material. One is by way of collisions that cause changes in the energy and momentum of the electron. The other ...
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Electrons in CRT

In a CRT, where do the ejected electrons go after they cause fluorescence on the screen, have they lost most of their energy, or do they actually go through the glass?
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Why photons transfer to electrons perpendicular momentum?

Linear antenna directed along z, photons (EM waves) propagate along x. Momentum of photons have only x component. Why electrons in antenna have z component of momentum?