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Questions tagged [charge]

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

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Prove that the electric field produce by a punctual charge is isotropic and radial

I would like to prove mathematically that the electric field produced by a punctual charge is isotropic and radial, i.e. $$\vec{E}(r,\phi,\theta)=E(r)\vec{e}_r\tag{1}$$ I think that this statement ...
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1answer
57 views

Does charge affect space-time?

Okay suppose there is an hypothetical particle called Nelectron which has mass = mass of electron but is electrically neutral. It has same spin and other quantum mechanical properties. Even the same ...
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0answers
31 views

Spherical capacitor with dielectrics [on hold]

Consider the following system: which consists of a conducting sphere with free charge 𝑄, a dielectric shell with permittivity $\epsilon_1$, another dielectric shell with permittivity $\epsilon_2$ ...
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Doubt in application of $GDT$ in electrostatics

Consider a volume charge distribution with continuous density $\rho({\bf r'})$. The electric field at ${\bf r}$ is: $${\bf E}({\bf r})=k\int_V \frac{\rho({\bf r'})}{R^2}\hat{\bf R}\, \mathrm dV$$ ...
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49 views

what is the deal with the poles of magnets

I am trying to figure out the reason why magnets are magnets. I understand that atoms become magnetic when there is a net direction of spin of electrons around the nucleus; however, I do not ...
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0answers
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Relation between electric charge and electric current distributions via velocity

Assume we have a charge $\rho(\vec{r},t)$ and current $\vec{\jmath}(\vec{r},t)$ distributions given in some region of space. From Maxwell's equations we know that the only relation between these two ...
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Electric field in the region of a spherical shell of inner radius A and outer radius B

Consider that we have a spherical of inner radius $A$ and outer radius $B$ where $B>A$. It is given the field in the three regions: $$E = \begin{cases} 0 & \text{at } R>a \\ K\frac{R^2-A^...
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2answers
66 views

Physical example of line charge

Electric field due to an infinite line charge, sheet of charge, point charge, etc are popular problems solved in most text on Gauss's law of electromagnetism. My question: does an (exact or ...
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Why alternating current produces electromagnetic waves? [duplicate]

So my question is: why alternating current produces electromagnetic waves? There are plenty of answers on google that state it as fact, but none answer why. I mean what is it about accelerating ...
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1answer
183 views

Is it possible that an electric field exists like $E=kx$?

Is it possible for an electric field $\vec{E}$ to exist such that its electric field intensity increases continuously, something like $E=kx$, while all the $\vec{E}$ pointing in the same direction?
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32 views

Quantifying potential energy

As per the definition of potential energy we kept a fixed charge, and in the presence of an electric field of the fixed charge, we release another charge of the same sign moving towards the fixed ...
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5answers
776 views

Doubts in understanding some concepts of potential energy

Let us consider a system of charges in space. The potential energy of the system of charges is determined by the amount of work done by the external force to assimilate the charges in that manner. But ...
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1answer
85 views

Lorentz force in superposition of two magnetic fields

When an electron with charge $q$ travels with velocity $v$ perpendicular to a magnetic field generated between two permanent magnets with field strength $B$ and no electric field, it experiences a ...
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24 views

tribo charge and work function - adiabatic vs vertical

I am interested in estimating relative tribo charging for different dielectric materials (insulators). I understand that I can use the work function difference between two materials to estimate ...
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8answers
6k views

How can neutral atoms have exactly zero electric field when there is a difference in the positions of the charges? [duplicate]

It is said that atoms with the same number of electrons as protons are electrically neutral, so they have no net charge or net electric field. A particle with charge cannot exist at the same position ...
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1answer
42 views

Confusion with electric field in a capacitor circuit

I'm having a confusion involving a couple of laws for a capacitor: $C = \frac{Q}{V} \propto \frac{1}{d}$. The capacitance, the amount of charge the capacitor can hold for a certain voltage between ...
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2answers
475 views

Charged enclosed by the sphere

I'm reviewing the book "Conquering the Physics GRE" for my upcoming Physics GRE. I came across this problem which I'm having trouble with understanding. In particular, I understand the solution that ...
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2answers
77 views

Why do I get static shock due to wool, but not due to cotton?

I have experienced electrostatic shock quite a lot of times due to woollen fiber, and as far as I can remember, never due to a cotton fiber. Any explanation as to why this happens? Edit I ...
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3answers
52 views

What actually current is? [closed]

Somebody help me visualizing current. What is it actually? Not just with mathematical relations but with something that we can visualize too.
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39 views

The charge given by a commutator

I saw in the text that $[Q,X]=cX$ and says the operator $X$ has charge $c$ under the generator $Q$. I tried to understand why the coefficient $c$ means the charge. So I used this relation to get the ...
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1answer
44 views

What electric and magnetic field lines look like in some examples?

I have seen this but couldn't understand so I wrote my own question. We all have learnt in school that electric field lines never intersect. Same is the case for magnetic field lines. But I have a ...
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2answers
85 views

Why does the flow of charge even create electricity? [closed]

Okay this is a question I’ve asked a lot of places but I always get its the flow of charges and it’s like a property. What I don’t really understand is how is this flow of charges creating electric ...
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2answers
59 views

What will happen when two conducting spheres are touched?

Suppose I have a conducting sphere with a charge of $$1.6 * 10^{-19} C. $$ What will happen when i touch this sphere with an identical neutral sphere? On which sphere will the charge reside?
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Are charges outside a conducting shell relevant to electric field inside the shell?

Assume there is a thin conducting shell with a fixed point charge in the center, Q. Scattered outside the shell (not on its surface) there are more fixed point charges. If I would like to know the ...
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3answers
80 views

How do leptons differ from one another?

All the leptons that I have come across have their native (matter) charges of -1 relative to the charge of an electron. Since they are all fundamental and are not made up of quarks, you can't ...
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0answers
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Dependence of electrostatic force on the surrounding medium

Two unlike point charges held at a fixed distance from each other. The force between them is measured. Then a brass rod is placed exactly in the midpoint of the line joining the 2 charges. Will the ...
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0answers
46 views

What is the origin of the electric charge? [duplicate]

What is the origin of the electric charge? In order to explain mass we had to postulate the existence of a quantum field (Higgs field), and we say that elementary particles get their mass by ...
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2answers
136 views

Electric charge of the Higgs field

The Higgs field is \begin{equation} \Phi = \left( \begin{array}{cc} \phi_{1} + i\phi_{2} \\ \phi_{3} + i\phi_{4} \end{array} \right) \tag{1} \end{equation} with $\phi_{1}$ and $\phi_{2}$ ...
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1answer
75 views

What would have happened if electron was considered positive?

We always keep on telling that current flows opposite to electron, since electron is negatively charged. And old people didn't knew, that it is electron which actually flows.. So, now if we correct ...
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0answers
38 views

What is the physical meaning of force between two halves of a charged sphere? [duplicate]

In this problem: Find the net force that the southern hemisphere of a uniformly charged sphere of charge density $\rho$ exerts on the northern hemisphere. Express your answer in terms of the radius ...
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1answer
38 views

What creates a negative charge in the material?

What creates a negative charge in the material? Is it an electron or a holon? Holons as I understand is a math. But what then creates an electrostatic repulsion? Is it still electron?
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2answers
68 views

Can a body have a charge of $0.8 × 10^{-19}\:\rm C$? Why or Why not? [closed]

Can a body have a charge of $0.8 × 10^{-19}\:\rm C$? Why or Why not? Please answer. Justify why and why not.
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3answers
50 views

What does leakage of charge in plate and isolated spherical capacitors mean?

I've read quite a lot of times about leakage of charge in capacitors, but what does it exactly mean? Do we see sparks? Or is it some current flow? Or something else? Say I have a charged sphere, so ...
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2answers
54 views

Differential equations for the LC circuit

On wikipedia one can find that the DE for an LC circuit is given by $$\ddot I+\frac{1}{LC}I=0$$In one of my papers however I found the equation $$\ddot Q+\frac{1}{LC}Q=0$$ and I've been confused by ...
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1answer
27 views

Why is the electric flux of a point charge inside a sphere not 0 since its a vector and all the field lines point outward?

I know that the magnitude of the total flux of a point charge is $\frac{q}{ϵ_0}$, and can follow the maths and reasoning behind it. But since flux is a vector, shouldnt it also have a direction? I ...
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2answers
41 views

Accuracy of Continuous Charge Distributions [duplicate]

In E&M, it is common to represent the charge on a body with a continuous, scalar charge density function. In reality though, the body contains discrete charges. I understand why this approximation ...
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4answers
63 views

How much energy is in a 75 kg human being? Including atomic and electrical (charge) [closed]

To calculate the energy in 75 kg of mass is easy with E = mc2. But, how to calculate how much charge are in all our atoms? It is, too, a gargantuan amount of energy.
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1answer
41 views

How electric current is defined in a metal wire?

How current is defined if in a metal wire both positive and negative charge exist? Isn't the total charge/time 0?
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0answers
26 views

What happens to a black hole with an extremely large net charge? [duplicate]

Suppose you repeatedly shoot low energy protons into a 4 solar mass non-rotating black hole, until it has so much net charge that a nearby proton experiences slightly more electrostatic repulsion than ...
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1answer
83 views

Does a charge in a gravitational field make a magnetic field?

I know that general relativity unifies the electric charge with the magnetic field via relative motion. So if I accelerate a charge then anyone in another inertial frame will see a magnetic field. ...
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1answer
23 views

Energy of continious charge distribution

In the book of Griffith intro to electrodynamics, on page 94, the energy of continuous charge distribution is derived in the following way: W(total energy) = $\frac{1}{2} \int\rho V d\tau$, where $\...
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2answers
42 views

Why don't we avoid self-interaction terms when we measure energy of a continuous charge distribution as we do for point charge distribution? [duplicate]

When we calculate the electrostatic potential energy for discrete point charges we make sure that while adding potential energy for individual charges we don't take the same charge and square it up by ...
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1answer
33 views

Differentiating between the characteristics of a positive and a negative charge

I am keen in knowing the physical difference between the fields produced by positive and negative charges. Thus far, I can only give myself an unsatisfactory answer: that in a field produced by a ...
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1answer
7 views

Fine particle adhesion to larger particles

Does static electricity cause smaller particles(dust size) to stick to larger particles? For example when doing gradations on fine aggregate samples from 1/2" size down to passing a 200 sieve size we ...
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1answer
51 views

Does ammonia emit microwaves?

Ammonia has an electric dipole moment which means that there is a charge located on one side of the molecule. The molecule can also exist in an inverted form with the charge located on the other side ...
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3answers
97 views

Can there be charges in free space without it being on some particle?

We see leptons and quarks possessing charges. Can there be charge in free space devoid of matter(neither leptons nor quarks or anything else)?
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3answers
80 views

Why can't we have charge field?

I learnt that everything is made of field, there is the electron field that occupy the entire universe and it will produce an electron which is an excitation of the field. This electron interacts with ...
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0answers
26 views

Charging two spheres by induction n times

There is a conducting sphere $S_1$ of radius 'r' mounted on an insulating handle. The sphere is given a charge Q. Another uncharged conducting sphere $S_2$ of radius R mounted on an insulating handle ...
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1answer
103 views

Why is there equal protons and electrons in the universe?

Matter and anti-matter are asymmetric. Why are protons and electrons symmetric? Would we still have galaxies and stars if there were a strong overall charge?
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1answer
79 views

Transfer of Electrical Charges

I'm having a lot of trouble understanding how charges transfer exactly. Suppose I have 3 particles $a,b,c$, $a$ is negatively charged, $b$ is positively charged and $c$ is neutral. We let the charges ...