# 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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### Single electron pumps, superconducting energy gap

I am seeking to find out how many electrons per gate cycle are pumped at different temperatures. The Single Electron Pump is made out of Al, with a $T_c=1.2\,\mathrm{K}$. This single electron pump is ...
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### Currents and the Speed of Light

Why is it that currents don't flow at the speed of light, but rather significant ratios of the speed of light. I don't have any formal reasoning as to why they would flow at the speed of light-I just ...
1k views

### How does electricity propagate in a conductor?

On a systems level, I understand that as electrons are pushed into a wire, there is a net field and a net electron velocity. And I've read that the net electron drift is slow. But electricity ...
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### Which derivation of drift velocity is correct?

In the derivation of drift velocity I have seen two variations and want to know which one's correct. $s=ut+\frac{at^2}{2}$ Assume that the drift velocity of any electron in any conductor is : ...
393 views

### What is the mass density distribution of an electron?

I am wondering if the mass density profile $\rho(\vec{r})$ has been characterized for atomic particles such as quarks and electrons. I am currently taking an intro class in quantum mechanics, and I ...
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### What happens in electron-electron collisions?

What are the results of high energy electron electron collisions? Are other particles created?
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### Is this picture of the electron dipole moment correct?

It's the electron spinning on its axis, and a magnetic moment shoots up. The direction of the North-South is opposite what I thought it should be. Why is the vector arrow pointing from North to ...
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### Do electrons need specific energies to excite electrons

Photons need specific energy levels, equal to the difference between two energy levels to excite an electron in an atom. Is this the same case with electrons that collide with atoms?
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### Distinguish electron-like and hole-like orbits in reciprocal space, with reference to the Brillouin Zones

So I have a solid state and thermodynamic exam next week and I've been going through some of the previous exams from years gone by to prepare. I came across this question "Distinguish electron-like ...
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### is it possible to flow current in open circuit?

First , i don't know much about chemistry and physics. I'm just a graphic designer but i have this question in my mind. I'm sorry if this question is too basic and use 'generic' language. As i know ...
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### Transfer of electron energy to atoms (heating up of matter by absorption of photons)

If an electron absorbs a photon to get exited to a higher energy level, it should either come back to same state or any other lower state by emitting the required photon. How then can there be a net ...
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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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### A question on lewis model

Electron affinity of chlorine = -349 kJ per mole. And, first ionization energy of sodium = 496 kJ per mole while energy required for combining= 147 kJ per mole. Isn't it a contradiction against ...
60 views

### Neutron decay and bet on the honor of physicists [closed]

As part of a bet which arose from a discussion between a friend of mine (physicist) and me (electrical engineer) I betted against him, I could easily find a simple question that doesn't involve more ...
512 views

### Measuring the spin of a single electron

Is it possible to measure the spin of a single electron? What papers have been published on answering this question? Would the measurement require a super sensitive SQUID, Superconductive Quantum ...
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### What is the math showing that the time reversed version of an electron is a positron? (+general time reversal question)

As in Wheeler's One Electron Universe idea, how do you show that electrons and positrons are time-reversed versions of each other? Do you just apply time reversal to an electron and out pops a ...
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### Definition of electric charge and proper explanation

Is there a definition of electric charge and proper explanation of it? It is said "Electric charge is the physical property of matter that causes it to experience a force when close to other ...
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### Charge gained due to photoelectric effect [closed]

Here I think, one beam will knock out just one electron. So, I am not able to even understand what the question says. Please someone give a hint as to what the question asks... As source of the ...
187 views

### drift velocity of electrons in a superconductor

is there a formula for the effective speed of electron currents inside superconductors? The formula for normal conductors is: $$V = \frac{I}{nAq}$$ I wonder if there are any changes to this ...
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### Difference between atom and elementary particle questioned

Hydrogen ion doesn't have one electron which clearly mean that it has only one proton..So hydrogen ion is only a proton. Am I right, please make it clear. If hydrogen ion and proton are same that how ...
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### Ballistic Conduction - Difference between Bosonic and Fermionic Transport

Ballistic Conduction is the phenomenon of an ideal conduction environment for quantum particles - for electrons the Ballistic Conduction is not infinity, but is proportional to the difference between ...
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### Why do people claim electrons are accelerating

A lot of text books mention that one of the reasons that classical mechanics failed to explain atomic and subatomic processes is that electrons which accelerate should release energy in the form of ...
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### Understanding drift velocities in currents

I have a doubt about the understanding of drift velocities in a current. My problem is that the textbook speaks very loosely about this. It's like: "well, if we apply a field $E$ then the charges will ...
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### Joule heating due to the (slow) electron drift velocity?

I understand the concept of why the signal speed is higher than the electron drift velocity, but I can't understand the concept of joule heating. If electrons move slow then how do they produce a lot ...
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### Why doesn't a stationary electron lose energy by radiating electric field (as per coulomb's law)?

If an electron in a universe constantly generates an electric field why does it not get annihilated ? I am confused because I read that an accelerating charge radiates and loses energy. So, why won't ...
280 views

### Why can free lithium atoms not take part in an Auger process?

Shouldn't it be possible for an incoming photon to excite one of the 1s electrons to a 2p state (or one of even higher energy) and then for the excited electron to drop back to 1s and kick out the 2s ...
153 views

### Why the K shell only contains 2 electrons?

It is written in my quantum physics book that the K shell contains only 2 electrons due to the Pauli principle. I know that if $n = 1, l = 0, m = 0$, then the Hilbert space associated to the spin is ...
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### Is speed of electrons in atoms a constant during explosions? [closed]

E.g. in exploding nuclear bomb or some other big explosions. I mean if the speed of electrons as waves/particles is a constant or changes according to other "forces" involved?
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### Is it reasonable to interpret the Lamb shift as vacuum induced Stark shifts?

This is a pretty hand-wavy question about interpretation of the Lamb shift. I understand that one can calculate the Lamb shift diagrammatically to get an accurate result, but there exist ...
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### Regarding the free electrons on the conductor

In a metal, why don’t the free electrons fall to the bottom of the metal due to gravity? Also, charges in a conductor are supposed to reside on the surface so why don’t the free electrons all go to ...
3k views

### How fast do electrons travel in an atomic orbital?

I am wondering how fast electrons travel inside of atomic electron orbitals. Surely there is a range of speeds? Is there a minimum speed? I am not asking about electron movement through a conductor.
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### If photons can be absorbed by electrons, wouldn't that mean light has a charge? [duplicate]

I am a biochemistry and molecular biology major. If photons can be absorbed by electrons, wouldn't that mean light has a charge? Electrons only attract positive charges. Isn't it?
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### The Deflecting System in a Hot Cathode Ray Tube

In an HCR-Tube, the deflecting system used to deviate the electron beam is made of positively charged plates. How is this justified? If, due to some malfunction, the electron beam deflects from its ...
31 views

### Planes of graphite crystal on diffraction experiments

When doing electron diffraction on graphite (a popular experiment for students at universities) always diffraction at these two planes with distances $d_1$ and $d_2$ are observed: But a plane ...
3k views

### Does 'electricity' have mass? Is 'electricity' tangible?

Background: I'm in a legal academic discussion about the status of electronic 'goods' and whether they qualify as 'goods' in the same way a chair and a pen do. In this context (and specifically at the ...
25 views

### Electron Spin Resonance and Free electrons

When performing an experiment to observe electron spin resonance, we use DPPH molecules as they contain an unpaired electron on one of the N atoms. My question is, why cant free electrons be used in ...
50 views

### B-field and Magnetic forces, speed of a particle

Let's say I have a particle moving perpendicular to a uniform magnetic field of magnitude $x \ T$, and it moves in circle with a fixed radius. How do I find the speed of this electron? Initially I ...
106 views

### How electrons act under rotating magnetic field?

I study Power Engineering in University. Today I asked my lecturer to explain me exactly how atom's electrons act under spinning rotor's magnetic field, that generated dynamic electricity. But he even ...
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### An electron has an initial velocity in B and E field [closed]

An electron has an initial velocity of (14.5j + 18.5k) km/s and a constant acceleration of (1.60×1012 m/s2)i in a region in which uniform electric and magnetic fields are present. If B =(400μT)i, find ...
164 views

### Do protons exchange photons with electrons?

I'm sorry for this question but, I just don't get it. According to the electromagnetic field theory, electrons repel each other by exchanging photons. How do protons attract electrons, by photon ...
112 views

### Couldn't we measure electrons with good enough technology? [duplicate]

I am a bit confused about the Heisenberg's Uncertainty Principle - just read about it in How to Teach Physics to Your Dog, by Chad Orzel. He states that the reason electrons can't be measured is ...
422 views

### How low can an electron go?

Title says it all - recently I encountered a strange homework exercise on de Broglie dual theory with an electron wavelength of few millimeters - which implies the velocity lower than 1 m/s. I ...
339 views

### Electron model under Maxwell's theory

I was not able to recall my memories, so: What is the formula that states the frequency of electrons revolving around nucleus is equal to the frequency of light (or photon) emitted (or radiated)? (I ...
116 views

### Path of an electron through an electric circuit

When a potential difference is applied across a conductor, and if an electron moves from the negative terminal of the battery and reaches the positive terminal, then I want to know if the electron ...
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### Microscopic fields inside a conductor

In a neutral conductor if we assume electrons as point charges, the electric field in the space between them cannot be identically zero. This microscopic field may be very weak. What if we were very ...
148 views

### When drift velocity equals thermal velocity?

In some papers, I can see the drift velocity of electrons equaling thermal velocity. Can anyone tell me when both almost equal each other?
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### Can electrons move through vacuum?

I studied that electronics is the branch of physics which deals with the practical applications of moving electrons through vacuum, semi-conductors and gasses. Can electrons move through vacuum?
1k views

### In electromagnetic radiation, how do electrons actually “move”?

I've always pictured EM radiation as a wave, in common drawings of radiation you would see it as a wave beam and that had clouded my understanding recently. Illustration on the simplest level: ...