Questions tagged [electrons]

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 does electricity need wires to flow?

If you drop a really heavy ball the ball's gravitational potential energy will turn into kinetic energy. If you place the same ball in the pool, the ball will still fall. A lot of kinetic energy will ...
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Why can't electrons absorb any energy (i.e. absorb some energy of the photons necessary and emit the residual)?

Recently I had a question in mind about the absorption of photons. Why is it that only specific energy levels can be absorbed by electrons? I mean, I get the idea that electrons in an atom have only ...
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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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Can I move the atom nucleus only?

I was wondering if it is possible to move the atom nucleus and leave behind the electrons? I can imagine that the electrons will follow the nucleus. But what if the speed of the nucleus is almost the ...
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Question on static electricity & electron transfer

Static electricity is caused by the transfer of electrons between substances right? For example, take a balloon and your hair. Both are stable and electrically neutral. So why would electrons jump ...
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Do battery electrons only move if there is a positive terminal at the end of the wire?

I'm sorry if this question may seem wrong in many cases. What would happen if we had a wire with the length of 1 kilometer that connected the two terminals of the battery? Do electrons care if the ...
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Momentum of an electron acting as a wave [closed]

Was working on a problem with electrons acting as waves in diffraction. Part of the question asked me to calculate the momentum of the electron. Since I was dealing with waves I used the following ...
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483 views

Electron degeneracy and helium flashes in stars

I have a question regarding the above mentioned. When a star have a mass of about 3-8 it does not go through the so-called helium flash phase, but instead just run along as nothing had happened, turn ...
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How do electrons actually move in a wire? [duplicate]

Do they jump from atom to atom or are they free-flowing? Where does resistance fit in? Do electrons physically HIT the atoms? If so, how do they hit atoms if the nucleus is small and far away from the ...
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How does the orbiting of electrons around nuclei START? [closed]

When electrons orbit a nucleus, their orbiting continues due to conservation of angular momentum, so I've read. But what causes an electron to orbit a nucleus in the first place? To be more precise, ...
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Are holes a fundamental particle? Are they a real thing or just a construct?

Some electronics textbooks seem to refer to holes as just a construct, while solid state physics textbooks seem to imply that holes are a very real thing. I understand that holes are vacancies (p-n ...
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Dependence of the energy of an electron on distance from the nucleus

I was going through an article given to me by my teacher which gave info about the influence of the positive nucleus on the electrons in the 's orbital', 'p orbital' and 'd orbital' respectively. Here ...
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Are free electrons truly free?

As this diagram shows, energy levels get closer together as they get higher. Is a free electron then truly free? Or is it in such a high (bound) state of energy that the transitions become nearly (but ...
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Pauli exclusion principle in an electron beam

Do electrons in an electron beam (cathode ray) follow the Pauli exclusion principle? Or in other words, does the Pauli exclusion principle apply for the beam of electrons?
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Ratio of electrons and protons in Universe

What is the relation between amount of electrons and protons in Universe? I expect that the Universe should not be charged, so the estimation is 1:1. But then, why there should be the same amount of ...
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Do electrons have a radius when they behave like a particle?

I know sometimes electrons behave like waves, but it sometimes can be seen as a particle. while it's a particle, does it have a radius? or, a volume? If it doesn't even have a volume, how can we still ...
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Can a free electron absorb a virtual photon even though it cannot absorb an ordinary photon?

Due to conservation laws a free electron,as I understand it, cannot absorb a photon. But in computing QED probabilities, diagrams are drawn showing emission and absorption of photons by an electron. ...
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Why does exchange lower energy with increasing electron density in Hartree-Fock

The Hartree-Fock equations include a term for the exchange interaction, which is usually explained as a repulsive force due to the Pauli exclusion principle. (It says so right in the description for ...
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How fast does an electron jump between orbitals?

I'm wondering what speed electrons jump from level to level. I've been told only that they emit light when doing so and need energy to be inputed in order to occupy orbitals closer to the nucleus. I ...
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What happens to an electron in a molecule once it has absorbed a photon and transitioned?

Say we have a molecule capable of absorbing a photon somewhere in the UV/Vis region of the electromagnetic spectrum. Once this electron has transitioned to a higher energy state, does it just stay ...
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How is the energy of an electron-shell related to the speed of electrons in that shell?

I am trying to gain an intuitive picture of what is referred to by "electron-shell energy". I have read that outer electron shells have higher energy than inner electron shells, and this seemed to ...
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Energy of electrons in wire

The Drude Model helped me quite a lot to visualize how current could flow in a circuit. However, there is still a point that I cannot grasp in the explanation given by some people when they talk about ...
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Will Positron Cause flow of electricity?

Recently someone told me about antimatter. Antimatter is something that is completely opposite to matter. What I would like to know is let's say this universe was made of Anti-Matter. So since the ...
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Where do free electrons come from?

Here's what I what to know... Atoms have a nucleus that's positively charged and the negative electrons flow around it. Well when you pull the negative electrons off the atom where do the new ...
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Why does the electric dipole moment of the electron tell us about its sphericity? [duplicate]

There are a bunch of experiments that claim to show that the electron is highly spherical by measuring the electron electric dipole moment. See e.g.: http://physicsworld.com/cws/article/news/2013/nov/...
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Electron Electric Field Mass?

I am confused of whether or not the expected electromagnetic field generated by the point-like electric charge of the electron distributed smoothly across space as a probability distribution creates ...
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Positive test charge

Protons have positive charge on them. Protons aren't mobile. So how can a positive test charge move from the negative terminal of a cell to the positive terminal and gain electric potential energy? ...
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Is an object's color/shine/texture dependent on its electrons only? If electrons are same then why are there so many different colors?

when we look at an object be it a metal or a non-metal are we looking at its electrons only, so then if all electrons are same then why do different chemicals or elements or objects have different ...
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Doubt about the working principle of a silicon solar cell

I'm studying crystalline solar cell and their working principle, but I still don't completely understand the process. First of all, I understand that we dope a pure crystalline silicon with boron and ...
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Electrons of conductors Free? [duplicate]

Are electrons of any conductor really free ? I mean are they always already moving or do they move only when electrostatic field of some sort is applied across them. I suppose if they were always ...
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Why is the drift velocity directly proportional to the electric field?

If I double the electric field, that should double the acceleration of electrons inside the conductor in the general direction of the electric field. But why does that double the drift velocity, and ...
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Can a positron decay without encountering an electron?

All the decays I read about involve electron - positron annihilation.
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Why are electron wavefunctions standing waves?

How can I convince myself that wavefunctions of electrons on molecular orbitals are indeed standing waves? Is it a consequence of the fact that electrons don't drift away from the molecule? In other ...
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1answer
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How does a high voltage produce ions

I was reading about gas discharge tubes and it said that when a high voltage is applied between the cathode and anode, electrons get pulled off the gas atoms. My question is how does this happen ...
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Why do the free electrons in N-type want to diffuse?

I'm trying to understand how a diode works and for this I've used(among other resources) the book written by Albert Malvino, Electronic Principles. Everywhere I read about this topic, it says that ...
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What happens if we give a single electron charge to a hollow metal sphere?

I found this related question: What happens to 5 electrons on a sphere? But this question describes the case when there can only be 5 electrons on that sphere at all times. The answer linked to the ...
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Free (unbound, so not bound to a nucleus) accelerated electron cannot emit/absorb a real photon?

I have read these questions: Can a free electron absorb a virtual photon even though it cannot absorb an ordinary photon? Where Michael Seifert says: It is entirely possible for a real electron ...
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Is the electron's magnetic dipole moment influenced by the measurement method?

The electric charge of an electron at rest is a constant value and is not influenced by the measurement instrument. The measurement instrument by itself can give more or less accurate result, but does ...
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Does charge of a metal charged by induction determine by which ends of the metal is grounded to?

Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand: Right diagram: When ground is touched with the ...
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1answer
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Ground state(s) of electron and dependence from temperature and gravitational potential

Reading this question What happens to an electron in a molecule once it has absorbed a photon and transitioned? it occurs the question to me is the ground state say of a hydrogen electron the only one?...
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Refractive index of plasma dependance on temperature

How does the refractive index of plasma changes with temperature? Temperature is not high enough for new ionization. Would it be like in gas p/T dependence ? http://farside.ph.utexas.edu/teaching/em/...
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Mathematical proof of an electron can't absorb a photon [duplicate]

How can we mathematically prove that a free electron can't absorb a photon totally?
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Is there something like “forced / induced electron-capture”?

I understand how electron-capture (also known as epsilon-decay) works and why it happens. As far as I know we are able to do "induced fission", i.e. in nuclear reactors. My question is: Is there a ...
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Einstein coefficients for emission/absorption and energy density

When dealing with a system of two energy levels $E_1$ and $E_2$ in laser theory, the following rate equations are written: $$\frac{d N_1}{dt} = A_{21}N_2 - B_{12} \rho ( \nu ) N_1 + B_{21} \rho ( \nu ...
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Electrons on Stern–Gerlach experiment

My questions about spin and negative charge of electrons. Stern-Gerlach experiment is very famous in order to find spin of electron. this video created by paris-sud university really well-explained on ...
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Why doesn't intensity of light affect the emission of electrons?

So electrons of specific atoms have a minimum amount of energy needed to escape the atom, called the work function, W. Now let's say that you emit a certain frequency of light, and $hf<W$. However, ...
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How does a free electron look like?

In a simple atom say hydrogen, there is an electron cloud which is spherical in shape. What about a free electron, how big or small will that cloud be? I think the term cloud here means the likelihood ...
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Spin-orbit coupling in itinerant electron systems

Itinerant electron systems are, e.g., metals. The electrons are not anymore localised at the atomic nucleus, but they behave as Bloch waves, which have a non-neglecting probability of travelling ...
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Possible inconsistency in Bohr atom model [closed]

It is well known that Bohr model is not totally right. But I recently discovered a very curious inconsistency (if I am right) which I haven't seen explained anywhere. The first postulate of Bohr ...
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The model of photon scattering, is actually about a complete absorbtion?

I was wondering about the things like Compton scattering. As I understand, it is an inelastic scattering of photon on free electron. Inelastic means, that photon changes it's angle and frequency. As ...