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 ...
3
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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 $\epsilon_2$ ...
0
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0answers
20 views
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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1answer
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 ...
1
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0answers
30 views
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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0answers
31 views
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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0answers
29 views
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 ...
2
votes
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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1answer
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 ...
2
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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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0answers
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
...
26
votes
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 ...
4
votes
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 ...
4
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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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1answer
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 ...
0
votes
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 ...
0
votes
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 ...
3
votes
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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1answer
50 views
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 ...
3
votes
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 ...
2
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0answers
12 views
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 ...
3
votes
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 ...
2
votes
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}$ ...
3
votes
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 ...
0
votes
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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votes
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 ...
0
votes
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 ...
0
votes
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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vote
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 ...
6
votes
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. ...
0
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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 $\...
-1
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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 ...
1
vote
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 ...
-1
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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 ...
3
votes
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?
1
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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 ...
