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

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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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23 views

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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97 views

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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60 views

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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1answer
173 views

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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3answers
102 views

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 ...
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125 views

Enhancing the QED $U(1)$ gauge symmetry

QED is a gauge theory based on $U(1)$ gauge symmetry, which gives rise to photon as the gauge boson mediating the interaction. Mathematically, I think it is perfectly allowed to implement a $U(1)\...
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78 views

What is the relation between charge and polarization?

On one hand, in this "Measurement of polarisation" lab manual, polarization is surface charge density, $P=\frac{Q}{A}$, in other words, charge an polarization are essentially the same thing. On the ...
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14 views

Measure a current from a charged surface caused by charge separation

I have separated a charge in an electric field like here (http://elektroniktutor.oszkim.de/grundlagen/gr_pict/coulomb5.gif) and I put the metal out of the field. The charge density on the surface of ...
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71 views

Point charge inside a electrically neutral cavity in conductor placed eccentrically, and effect of external electric field if switched on

bear with me, but i would like a definite answer, now, starting off the external charge density on the outer surface of sphere WILL be uniform by unique solution of Laplace equation and letting the ...
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93 views

Why doesn't gravity have charges?

All other forces have some kind of charge system, electromagnetism has positive and negative, weak force has hypercharges, and strong force has colors. Why doesn't gravity have anything like these?
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97 views

How does a charge distribution evolve with time? (in classical electrodynamics)

It is often stated that, in classical electrodynamics, the electric and magnetic fields determine uni vocally the dynamics of a charge distribution distribution (how it evolves in time). I can more or ...
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84 views

Coulomb's Law and conversion of nano-columbs/coulombs

This is not a homework problem. I am working ahead for my Electricity and Magnetism course for next quarter and this is a Chapter 25 video tutor solution question pearson put out where they do a short ...
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63 views

Distribution of Electric Charge on the surface of Sphere - simple explanation? [duplicate]

Which basic physics principle could I use to formulate a simple explanation of the homogeneous distribution of electric charge on the surface of a hollow metallic sphere? P.S.: targeted audience with ...
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32 views

Extreme charge density in thin capacitor plates

Suppose we made a 1 square meter parallel plate capacitor from two sheets of graphene separated by a very strong dielectric of arbitrary thickness. Then we charge the capacitor just short of the ...
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2answers
76 views

Are charges always uniformly distributed on conductors?

As the title says. For example, if I take a fat metal wire with non-negligible thickness, and then wind it into a spiral, but such that none of the parts touch one another (there are no topological '...
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141 views

Problem related to application of Maxwell's equation for point charge moving uniformly

Maxwell's 4th equation which describes magnetic field, has two terms: $$ \oint \mathbf{B}\cdot d\mathbf{l}=\mu I+\mu \varepsilon \frac{\mathrm{d}\Phi}{\mathrm{d}t}$$ Now, I wanted to derive the ...
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38 views

Uniformly charged disk

A uniformly charged disk is an isolant or a conductor? Or could it be both of them? I only know its radius and its surface charge density, which is uniform throughout the disk.
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49 views

What is exactly the “negative” charge?

If we take a particle, a non neutral one, we know we can measure a distribution of charge on it. Now, the fact that this particle may have positive distribution of electric charge it's ok. Maybe ...
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77 views

How can charge be squared?

In many Wikipedia articles I have come across it refers to a Coulomb squared. What does this mean intuitively? i.e. http://en.wikipedia.org/wiki/Farad (this was the most recent place I came across ...
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136 views

What does “charge” actually mean? [duplicate]

I know that a charged particle is defined as a particle that experiences a force in an electric field, as explained in this post: What does a subatomic charge actually mean? However, I still don't ...
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193 views

In which experiments the charge to mass ratio of proton was determined?

Are there experiments where the charge to mass ratio for protons have been determined in the same way as in Thompson’s experiments (where he determined the charge to mass ratio of electron) but with ...
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1answer
51 views

The point of charge neutrality in the Hydrogen Atom

If we treat the Hydrogen Atom like the Bohr model then we have a proton in the center with an electron orbiting at some radius (the Bohr radius). In this picture you can imagine the electric field ...
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93 views

Other values of mass of the electron and the charge of the electron?

Are there whatever experimental data other than Millikan Oil Droplet experiments data and Stoney calculations from electrolysis low, or some experimental indications pointed on the possibility that ...
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28 views

If iI have a capacitor connected to a battery can the negative charge be sent to an insulated object

If I have a capacitor permanently connected to a battery, that is lets say setting in a plastic bowl, and then run a wire from the negative of the battery to a non grounded object, say a metal can ...
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58 views

The force applied by two charges on each other when there is another charge nearby them

QUESTION 1 Let me give two simple scene of charged particles to make you understand my question. There is a fixed positive charged particle in the center. Scenerio 1 : A fixed negative charged ...
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45 views

Where does the net charge on a hemisphere appear to act from?

I was wondering if, like centre of mass, there is anything called "centre of charge".
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40 views

Average distance between electrons on a parallel plate capacitor

I came across this question in an old exam paper and I am interested in the way it was marked. The 'correct' answer doesn't seem to be as correct as it could be. Calculate the average distance ...
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46 views

A 100 000 km wire in contact with a positively charged sphere

A long copper wire (see the picture), placed somewhere in the outer-space, having the length $L=100000 km$ and the cross section $S=1 cm^2$, comes in contact at one of its ends ($x = 0$) with a $+Q$ ...
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48 views

Capacitance question

A capacitors capacitance, C is equal to Q/V right? If Q was somehow cut in half, would the potential difference also be cut in half, since V is directly proportional to Q? And if so, Its C would be ...
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29 views

Dipole moment of a displaced charge distribution [duplicate]

This one is part b) of the problem I asked a day ago. Special thanks to MarkMitchison and sbp on the first part. I finally got it. (How can I prove that the dipole moment is zero?). Alright, back to ...
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144 views

Can the surface charge density be negative somewhere on the inner surface of a spherical conductor shell?

A positive charge $q$ is located off-centre inside a conducting spherical shell. We know that the total charge on the inner surface of the shell is $-q$. Is the surface charge density negative over ...
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16 views

Find Electric Field at certain radii for a sphere

If radius of non-conducting sphere is R=4cm, find Electric field at r1=3 cm (for inner Gaussian surface) and r2=6cm(for outer Gaussian surface) Volume charge density is given as: ρ = c r^2 where c ...
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24 views

Explanation to the flow of charge

I came across a really cool Cymatics video: There is one part in the video which is unclear to me. Please refer to the snapshot below taken at 05:15. I see the equipment being close to a Van de ...
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119 views

Radially symmetric charge distribution (dipole moment) [closed]

a) There's a radially symmetric charge density $\rho(r)$ centered around the origin. Determine the dipolemoment of that charge density. b) Let $\rho(r)$ be an arbitrary charge density now. Under ...
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100 views

Charges on capacitor after full charge by battery

When the charging is finished what will be the charge on an ideal parallel plate capacitor ? To be specific what are the charges on different faces of the 2 plates ? All the books say, after 100% ...
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45 views

Dipole Moment (spherical/arbitrary charge density) [duplicate]

I'm new here. I got to this website while searching for links to fill my gaps on some topics. I have found some amazing posts for many different topics. Just amazing. Anyway, I'm currently dealing ...
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57 views

Do virtual photons give particle charges?

I think the electric field is due to the exchange of virtual photons constantly emitted by the point charged particle such as an electron, does this apply to proton which is consisted of quarks? does ...
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1answer
54 views

Could someone simply explain how a railgun works?

Could someone simply explain how a railgun works? What could possibly accelerate an object that fast in such a short distance? I've heard it has to do with current between two rails, but I simply do ...
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1answer
116 views

How strong a magnetic field would be needed to deflect cosmic rays?

How strong a magnetic field would be needed to deflect cosmic rays? For example, lets imagine we wanted to protect the occupants of the International Space Station from cosmic rays. I assume we would ...
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1answer
136 views

Does a Tesla coil work in space?

If I took a Tesla coil into space, and then turned it on near, but not touching metal objects- would charge jump to the metal objects? It's my understanding I wouldn't see a flash, since the lightning ...
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1answer
49 views

Time derivative of Noether charge

I understand that the Noether charge can be written as $$ Q= \int d^3 x J^0$$ and the time derivative of the Noether charge is zero $$ \dot Q=0 $$ but how would you explicitly calculate it?
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79 views

Is antimatter attracted to matter by its opposite electric charge?

As it is said by many physicists that antimatter is just opposite of matter; it has opposite charge of matter, then is there is any possibility that antimatter is attracted to matter? For example - ...
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53 views

What is the “practical purpose” of Gaussian surfaces?

Without having the concept of a Gaussian surface, we know that charges induce fields in proportion to quantity. Now to take a common example, when describing flux through a (physical) surface it is ...
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87 views

Is this charge density function, from a problem in Griffiths' book, a physically valid density?

This is from the book on electrodynamics by Griffiths: A sphere of radius $R$, centered at the origin, carries charge density $$\rho(r,\theta)= k(R/r^2)(R-2r)\sin(\theta)$$ where $k$ is ...
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65 views

Validity of law of charge conservation

Charging by induction and earthing gives an object a net charge but why does the law of charge conservation still hold in this case?
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390 views

Derivation of capacitive reactance

Let $Q(t)$ be the charge stored in a capacitor $C$ in $t$ time for alternating current. Now, $$\displaystyle Q(t)=Q(0)+\int_{0}^{t}I(t)dt\\=Q(0)+\int_{0}^{t}I_oe^{j\omega t}dt\\=Q(0)+\frac{I_oe^{j\...
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2answers
134 views

Why is the charge of a proton positive? [duplicate]

Is there a reason that a proton has a positive charge while an electron has a negative charge? Are these just names that were given to the charges or was there a reason for making a proton have a ...
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68 views

signal from uniformly moving charge

As a charge moves, its field changes, and this change can only be propagated outward at the speed of light. Thus the field lines will be curves that keep changing apparent source point and direction. ...
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100 views

Where is the fallacy in this issue related to electric charge quantization? [closed]

Suppose there are two identical conducting objects; one with 5 units of positive charge and the other is uncharged. Initially these are separated and later these are brought into contact. I guess net ...