# Tag Info

5

Ill answer the second part of your question about effective mass and quasiparticles, since I see that CuriousOne has answered the rest better than I could have. In a metal or semiconductor, the electron is not in the same free state it would be in a vacuum. It is bound to (although delocalised within) a lattice of positive ions. So its dispersion ...

9

Your question touches the question of ontology in particle physics. Historically we are used to be thinking of particles as tiny independent entities that behave according to some laws of motion. This stems from the atomistic theory of matter, which was developed some two thousand years ago from the starting point of what would happen if we could split ...

1

Then does all charges, no matter how much charged are they, ionize the material around them since distance can get smaller and therefore electric field gets bigger. Consequently, the electric field exerted by the charge would be higher than the electrical breakdown limit of the material around it. Let's say you magically stick a (positive) charge inside a ...

3

The neutron is not a fundamental particle. It carries no electric charge, yet it can interact with photons as its components - the quarks - carry electric charge and thus couple to photons. Macroscopically/classical, these interactions cancel out since its net charge is zero, but quantumly, there is a very big difference between objects with charged ...

2

A propagating EM wave is a field that needs no charges. Likewise, a propagating gravitational wave is a field that needs no masses. However in both cases there is no way (classically) to create the wave without a charge/mass. Considering EM, the divergence of the field is zero unless there is a charge, or put another way since field lines can only begin and ...

1

I don't know cases in which the e.m. field can be produced without charges, however I can tell you how to produce an e.m. field without electric charges. Take a neutral particle, meet it with its antiparticle, have them clash, and you'll get gamma rays. The latter are electromagnetic. Also, gamma emission from excited nuclei, has not much to do with the ...

0

The explanation for this is partly Gauss' law and partly the nature of metal. Metals have free electrons that move to try to compensate for electric fields. The free electrons near the surface on the inside of the sphere will have an uneven distribution if the point charge is off-centre. These electrons will counteract the effect of the positive charge ...

0

You could try spraying them with an ion wind from a charged needle. If you need an interior rather than surface charge then you will probably need to hit them with a beam of charged particles of enough energy to penetrate to the interior. The easiest would be to charge them negatively using an electron beam or beta emitting radio isotope. How long they would ...

3

HInt: Force on what? You need some charge to exert the force on. Otherwise you can calculate the electric field. To do that, you need to know the number of protons in $100$ g of normal matter. Since electrons don't weight anything and (at this level of approximation) there are the same number of neutrons and protons....

2

The Rydberg electron - the electron in the high n level - is highly polarizable and very weakly held. The binding energy of the electron is very small. A small electric field will distort the wavefunction of the Rydberg electron so that it spends more time on one side of the atom than the other. The result is the formation of dipole. Rydberg electrons in ...

1

In short: the laws of conservation (angular momentum, charge, mass-energy, etc.) still work during the process of creation of a black hole. So if a star had some angular momentum/charge before it collapsed, the resulting black hole will also have some (assuming the angular momentum/charge was not radiated away during the collapse). Also, the claim that ...

0

The concept of photon exchange comes from Feynman diagrams and the exchange is of a virtual photon, a four vector carrying the quantum numbers of the photon ( or whatever the off mass shell particle is) but the mass is not on the mass shell, and has a different value according to the calculation of the process under study. This is a simple description of ...

1

The frequencies are the same but they are 180 degrees out of phase with each other.

0

Since the field of each charged particle extends to infinity, the fields of two particles are "in contact" with each other (no "communication" is necessary). When the charges are not equal (+ & -), the fields "cancel" each other along the line connecting their centers. This causes the attraction of the particles. When the charges are the same (+ & + ...

0

This is just a property of matter, found in nature. It was found, that very hot matter tends to "share" electrons between all members (atoms). If you have take, for example, a hydrogen cloud and then take all electrons out of it by magic, you will see a could of protons. But it will be unstable. Protons will repulse each other until the cloud will be ...

1

I don't think that quasineutrality is "a required condition", but is a property of most plasmas. Quasineutrality is the tendency for plasmas to attain electrical neutrality. It means that if a neutral plasma (with equal numbers of electrons and ions), should generate a region with a slight electrical charge, then because (a) the electric force is huge ...

0

I don't think that quasineutrality is "a required condition", but is a property of most plasmas. Quasineutrality is the tendency for plasmas to attain electrical neutrality. It means that if a neutral plasma (with equal numbers of electrons and ions), should generate a region with a slight electrical charge, then because (a) the electric force is huge ...

0

It is common knowledge that electrons are mobile and therefore used in conductivity. Electrons move freely within the structure of an atom but protons are bound in the nucleus and therefore immobile. Conductivity will therefore occur when electrons move from one atom to another and not protons due to their immobility. We now learn particles are involved in ...

1

The original system as described in inherently unstable (or at best metastable). According to Earnshaw's Theorem, "a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges" http://en.wikipedia.org/wiki/Earnshaw's_theorem So the introduction of the slightest ...

1

Now per QED, electrical charges interactions are effected by photons. Suppose you are one of the two charges. How do you know to attract or repel the other charge? You want something that does not exist - intuitive picture of physical process within a theory which is a demonstration of how far can one go with mathematisation of experience and ignoring ...

0

The attraction of unlike charges and the repulsion of like charges is an experimental observation that has to be included in any model of electromagnetic reactions When talking of photons one is in the quantum mechanical regime. As in classical electrodynamics the sign of the charge defines the potential, attractive or repulsive, between the two charges, ...

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