# Tagged Questions

A fundamental property of matter which causes it to experience electromagnetic forces.

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### (boundary conditions) Interface between two lossless media

I'm wondering why there's usually no free charges nor free currents in the interface between two lossless media? no free current "I guess" is due to the insulating nature of a lossless media but why ...
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### Why doesn't an electron's charge rip the electron apart? [duplicate]

Like charges repel. What keeps an electron's charge from repelling itself? This problem would come up if an electron was divisible and its parts had fractional charge. A related question is, ...
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### Why is the mass of neutrino expressed in electronvolts?

The definition of electronvolt (eV) from wiki is In physics, the electronvolt (symbol eV; also written electron volt) is a unit of energy equal to approximately 160 zeptojoules (symbol zJ) or 1.6×...
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### Does the electromagnetic force “split” at lower than normal energies?

Since we have working models for forces "combining" or being describable via a single framework at higher energies (such as the "electroweak" force and the aim of GUTs), does electromagnetism split ...
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### if there is no electric field then any charge exists or not? [closed]

If we assume a region of space in which there is no electric field, can we say that no electric charge exists? I think that there is no electric charge particles to create electric field for this ...
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### Protons, electrons and integers [duplicate]

From this calculation (http://uk.answers.yahoo.com/question/index?qid=20080724101956AA4zed1), two protons seperated by the distance of one atom feel the electromagnetic force repelling them 1.239*10^...
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### Kaluza Klein charge

If I take a $(d+1)$ dimensional Einstein Hilbert Lagrangian $L_{d+1}=\sqrt{-\hat{g}} \hat{R}$ and perform a standard Kaluza Klein dimensional reduction by periodically identifying one direction, let's ...
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### Are charges absolute or relative?

The charge of a particle is (mostly) an intrinsic property of the particle. One of the few elementary particles that doesn't have a charge are neutrino's. Does that mean that it is still possible ...
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### How did scientists manage to measure the charge of electron so precisely?

According to the latest CODATA reports the charge of electron is known very precisely $\approx 1.6021765314 \times 10^{-19}$. My question is: How is this charge determined with such high precision? ...
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### Can polarization occur if both charges are neutral?

If I keep neutral conductive pieces of some metal close to a neutral conductive sheet, what will happen? Will any of them get polarized or nothing will happen. My guess is nothing will happen as for ...
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### Why does current density changes but not current? [closed]

let us assume that we have a conductor with a specified resistance ( case 1 ) and a normal conductor ( case 2 ) as shown in the figure , and now we apply an external electric field with a battery on ...
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### Charge on Earth [closed]

We know that the Earth is neutral. But what will happen if the Earth becomes negatively charged or positively charged somehow?
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### Why is spacetime curved by mass but not charge [duplicate]

According to general relativity theory, the deformation of spacetime is proportional to energy tensor $$T_{\mu\nu}.$$ $$R_{\mu\nu}-\frac{1}{2}g_{\mu\nu}R = 8\pi G T_{\mu\nu}.$$ Does it mean that ...
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### Will charges attract or repel?

If the universe consist of only two particles namely electron and proton, and if they are separated away by huge distance, they will still attract each other. Can we prove it without using Coulomb's ...
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### Force from a large conducting plate [closed]

How can I find the distance to a test-charge, hoovering below a conducting plate? Newtons laws applies.  According to this information, I conclude that the force is equal zero. It is not moving....
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### Electron gun; potentials around charged plates

I know that an electron gun releases electrons by thermionic emission and accelerate the electron through charged plates, and that the electrons are not gaining any energy after they leave the gap ...
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### What is the difference between charged body and conductors?

In charged bodies,charges can be uniformly distributed all over it's volume, but in conductors charges always lies on it's surface. Please tell me the difference between charged bodies and conductors?...
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### How exactly are the relative strengths of gravity and electromagnetism quantified? [duplicate]

I've often heard it said that gravity is much weaker than electromagnetism, and after looking at several questions on SE, I feel that I've got at least a qualitative handle on the concept -- gravity ...
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### Why is it true that Laplace's equation does not hold within the sphere in this case?

Find the average potential over a spherical surface of radius $R$ due to a point charge $q$ located inside. (In this case Laplace's equation does not hold within the sphere) This is a question from ...
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### Is the electric field inside a conductor always zero? [duplicate]

We just learned in physics that a field inside a conductor is zero. My question is, is this always true? For example, what about if you were inside a hollow iron sphere 10 feet from a hugely ...
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### Charge distribution in electron

In the Wikipedia article Classical electron radius in calculation of radius of electron. Charge distribution of electron described as $$\rho(r)= \frac{q}{4{\pi}Rr^2}$$for $r\leq R$. This is variable ...
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### Gauss's law giving incorrect answer

Let's consider two concentric spherical shells, one of radius $R$ and one of radius $R - \Delta R$. The outer shell is negatively charged and the inner shell positively, but both the shells have net ...
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### Distribution of surface charges in an electric circuit

I'm reading Sherwood and Chabay's brilliant textbook Matter and Interactions, in particular the section that deals with how the surface charges in an electric circuit distribute themselves to generate ...
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### If we consider the electric field to act upon charges with a force, how does it stay in line with Newton's laws?

This should be a relatively simple question. Let's say we have a constant electric field $\textbf{E}$ in a conductor. The electric current density would then be $$\textbf{j}=\rho \textbf{v}$$ where ...