# Tag Info

1

Take a look at the Drude model. It gives a fairly intuitive way to look at conductivity in solids. Although later proved to be slightly incorrect due to the ignorance of quantum effects, it does the job for a classical explanation. One can reason as to how heat is generated in the conducter in a classical manner from the Drude model. As the electrons move ...

2

what happened with the electrons in this process? After fission, the potential that bound the 92 electrons changes. The alpha has too much kinetic energy and cannot trap the two electrons it needs. It will pick up electrons at it comes to rest in the material or the air. The remaining, now Thorium, nucleus reorganizes and the electrons are bound in the ...

0

The electrons stay with the daughter nucleus. A good way to see this is by imagining the decay. Imagine an atom. A helium nucleus shoots out. By the definition of a nucleus, it has no electrons. Therefore, the electrons must still be on the atom.

0

Two electrons when they move experience these forces $$F_{electrostatic repulsion } = \frac{ke^2}{r^2}$$ And, $$F_{magnetic attraction} = \frac{μ_0 . e^2 v^2}{4 \pi . r^2}$$ As you can see from the formulae for attraction there must be a velocity. For the two forces to be the same the speed of the electrons must as fast as light, practically these two ...

0

you can check the discussion here. There is a certain case in which a phonon mediates attraction between two electrons. Indeed, acoustic phonons correspond to a slowly varying in-space displacement of atoms which produces a charge. This charge, in turn, results in an electric potential for the electrons. This means that the electron distorts the crystal ...

0

In certain scenarios there can be a magnetic attraction, but the electrostatic replusion will greatly overpower it.

1

No. As has been said, the raindrop is not emitting the light, it is just acting as an optical device that deflects light emitted by the sun. However, the spectral lines you would expect to see in sunlight refracted by a prism will not, repeat NOT, be seen. The mechanism that produces rainbows is very different than the mechanism that produces a spectrum ...

2

Can we have electronics with charge carriers OTHER than electrons? Yes, see what Sebastian said above. And see the physicsworld article Taming light at the nanoscale: "Look around, and you will probably see numerous electronic and optical gadgets, such as mobile phones, personal digital assistants, laptops, TVs and digital cameras. These may all do ...

4

Depending on your view, there is electronics with other charge carriers. It is commonplace to have semiconductor devices where the relevant carriers are holes! Furthermore, batteries and electrolysis relies heavily on ions as charge carriers (but hardly count as electronics). I guess genuine electronics with ions will be difficult as charge carrier mobility ...

0

You need something that can be conducted along the wire to power electronics; if you were to get protons, rather than spreading from atom to atom you'd just end up changing the element of the atom or splitting it. The closest thing that you can do other than add electrons is chemically charge it, as in replace the batteries.

1

Presumably you are referring to semiconductors. A hole physically exists in that it is the absence of an electron. Just like a hole in a piece of paper physically exists. However, if you are asking whether the hole is a particle, then no, it does not physically exist. In a semiconductor, we deal with electron hole pair (EHP) generation. When this happens, ...

2

Ok, the previous answer by Alchemist is totally reasonable, but I think we could add a bit of "what is real?" into this discussion without getting metaphysical. A hole is a perfectly well-defined mathematical concept, in the same way that an electron is a perfectly well-defined mathematical concept. The mathematical concept of an electron in the theory of ...

3

That is true indeed. A hole has no physical existence. It is just the absence of an electron that creates the illusion of a positive charge at that point. You can find it in Boylested Electronic Devices and Circuit Theory that it's a theoretical thing.

1

Electrons move quickly because they have low inertia. Their mass is so low that a small push gets them to a high speed.

0

What's tabulated by the Particle Data Group is the electron's magnetic moment anomaly, $$a = \frac{\mu_\mathrm e}{\mu_B} - 1 = \frac{g-2}{2},$$ which has a magnitude of $a\approx10^{-3}$ and is currently known to about eleven decimal places. (Note that this does not mean we know the electron's magnetic moment to fourteen decimal places: there is also ...

3

I used to make X-ray tubes for a living... and the "right" answer to this question would run the length of a book. So just a few pointers. I don't expect that you would be able to create an electron tube after this - at least not one that lasts. Note also that if you do get it to work, it will produce dangerous (X ray) radiation. And unless you understand ...

1

The situation is entirely different from the double slit experiment! In the double slit experiment, one electron propagates through the slits, its parts interfere, thus we have a density matrix like (this prepares a pure state $\lvert\psi\rangle = \frac{1}{\sqrt{2}} (\lvert 1 \rangle + \lvert 2 \rangle)$): $$\rho = \frac 1 2 \begin{pmatrix} 1 & 1 \\ 1 ... 1 What's the effect of a resistor? It's a component that dissipates energy end thus lowers the voltage. So what is voltage? It's the strength of the field that moves the electrons, while current represents the number of electrons flowing through the wire. Free electrons can be stopped all together or slowed all together, but it's not possible to select only ... 1 Angular momentum is a conserved quantity (in a closed system) and this is true also for the angular momentum that is carried by the electromagnetic (EM) field. This conservation is a manifestation of rotational symmetry and the azimuthal part of the EM field emitted must be single valued. In other words, when rotating the EM field in the azimuthal (\phi) ... 3 The water droplets that create a rainbow are not emitting the light that you see in a rainbow; if they were, you would see a glowing cloud of consistent color, not a rainbow. The rainbow is formed by sunlight refracting and reflecting through water droplets in the air; the water refracts through the "front" of the drop, reflects off the "back," and refracts ... 1 The answer to As an electron drops from a higher energy level to a lower energy level, can it be modeled as a the continuous movement of a charged body, therefore causing a magnetic field to be generated around it? is "Yes, but only trivially." That is, you could probably work backwards from the far-field radiation to some imagined moving source ... 5 An atomic species defined by its number of protons (usually denoted Z) and its number of neutrons (usually denoted N) is called a nuclide. For atomic species the number of electrons is the same as the number of protons (i.e. Z). You are right to assume that the nuclide of a single nuclide solid will typically determine its melting point and hardness ... 2 It's not even that simple, as different crystal structures of a given molecule can have different melting points, e.g. Ice-V . I don't remember enough solid-state physics to state whether any elements form different crystal structures with different melting points, but certainly, for example, the hardness of carbon depends on whether it's diamond or ... 3 Atoms and molecules that have high boiling points and melting points have strong intermolecular bonds that resist form change. Therefore, to make a material win these properties, in general your you want long chained molecules. 0 It depends on the probability of interaction. This probability is computed using Fermi's golden rule, and it involves the strength of the interaction and the number of allowed final states. Weaker interactions means higher probabilities of going through the atom. Some examples: Neutrinos only feel the weak interaction, so their probability of going ... 1 Any sufficiently fast particle can go through the atom since the repulsing force is finite and you can prepare a projectile with a high enough energy. 0 Most sub-atomic particles can. In the Rutherford gold foil experiment, alpha particles (helium nuclei) often went through atoms. Beta particles (high speed electrons) can go through paper. There are more than a billion neutrinos going through you every single day. 2 You say the lamp is plugged into a AC outlet, but then talk of a "wall switch". Apparently you mean that this switch controls the power to the outlet, and that a switch on the lamp is kept on, or that the lamp has no switch. If so, you should clarify this as a switched AC outlet, since most aren't. In the case of a switched AC outlet, the switch will be ... 1 The electrons are in random motion within the cord even when it is plugged and not switched on. The motion of the electrons in this is case is random i.e., there is no preferred direction of motion of electrons or vector sum of all the thermal velocities is zero. Each electron within this conductor acts like a point source of electric filed and these micro ... 2 Depending on the location of the switch, the answer will change. A properly wired lamp would have no signal on the live (phase) wire, and therefore there would be no field. However, if you interrupt the neutral wire (or the switch is in the lamp, not the wall) then you will have a varying AC field because the voltage on the wire changes (and thus a small ... 1 HyperLuminal asked: "Does that mean that electrons are infinitely stable?" Think about Dirac's model of an electron, which includes left and right handed contributions. Now add the (Nobel-worthy) Brout-Englert-Higgs idea, that the left-handed bit interacts with a condensate of weak hypercharge, while the right-handed bit does not. This suggests a ... 0 Current is conducted due to loosely held electrons present in a metallic lattice. (refer metallic bond on wiki). Note the electrons are loosely held to the neucleus and they are not free to fly away. When a potential difference is applied across a metallic conductor these electrons move from low potential to high potential giving rise to an electric current ... 1$$ \newcommand{\ket}[1]{| #1 \rangle}  I'll try to answer the last two. with an arbitrary superposition, the probability density for the electron could be anything - can we actually find the coefficients of the superposition an electron actually is in? I'm a little confused about what you mean here. If we are given $\ket{\psi}$ as a combination of, ...

2

Regarding your first two points: The symmetry axis of an orbital is free for a free atom. If it's bound to some other atom through one of these one-dimensionally elongated orbitals, the orientation of one orbital is fixed. If you take e.g. carbon, silicon or germanium, you have one s orbital and three p orbitals, which are oriented perpendicular to each ...

34

The statement is true for decays, where lifetimes can be measured. It is not true for interactions though. A suicidal electron meeting a positron has a good probability to disappear, together with the positron, into two gamma rays, at low energies. Electron-positron annihilation It is intriguing that this is not true for neutrinos. If an electron ...

12

This is not exactly true. It is believed that net charge is conserved, but there is a weak process called electron capture, where an electron is captured by a nucleus, (usually from an inner "orbital" so there is a spectroscopic signature), a neutrino is emitted and a proton changes to a neutron. So therefore your textbook is wrong!

182

Imagine you are an electron. You have decided you have lived long enough, and wish to decay. What are your options, here? Gell-Mann said that in particle physics, "whatever is not forbidden is mandatory," so if we can identify something you can decay to, you should do that. We'll go to your own rest frame--any decay you can do has to occur in all reference ...

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