Questions tagged [charge]

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

Filter by
Sorted by
Tagged with
12
votes
2answers
213 views

Evaporation of large charged black holes

Black holes evaporate (Hawking Radiation) acting as black bodies with the temperature inversely proportional to the mass. No physical process, be it evaporation or any other "trick", can make a black ...
1
vote
0answers
91 views

Charge distribution on a hollow conducting cube [closed]

Suppose we have a charged hollow conducting cube, will the charge be uniformly distributed over the surface of the cube? I know that the electric field will be zero everywhere inside the cube but to ...
1
vote
1answer
59 views

Gauss's Law on Parallel Conducting Plates

I have a question regarding the application of Gauss's law to find the E-fields produced by two parallel conducting plates. My textbook (Halliday and Resnick 9e) states that there is no E-field above ...
2
votes
1answer
179 views

Contradictions in electric field of infinite uniform charge distribution [duplicate]

This question stems from the exercise 2.50 of Griffith's Introduction to Electrodynamics, which I am rereading. In the problem, he asks to find the charge density of a volume when the electric field ...
2
votes
1answer
72 views

Why does one Coulomb equal that strange number? [duplicate]

Why is one Coulomb equal to 6.24 *10^18 ? This number is weird . why wasn't it a nice number like 10^20. I have some guesses about this.
1
vote
2answers
102 views

The value of $E$ in the LHS of Gauss law equation

Suppose there are multiple point charges in a region and I only take the Gaussian surface which encloses only one of the charges $q$. I have read that the $E$ term on the LHS of the Gauss law equation ...
3
votes
3answers
502 views

What's the explanation of 'paper pieces and comb experiment' about static electricity on atomic level?

I know that the charged comb induces static electricity in the paper pieces.how does that happen? Do the atoms in the paper get ionized,the same what happens when the comb was rubbed on hair?please ...
0
votes
1answer
431 views

Potential of a non-uniformly charged spherical shell

This question is taken from The Feynman Lectures on electromagnetism. A spherical shell with surface charge density $\sigma = \sigma_0 \cos \theta$ is given. The potential at any external point is ...
0
votes
1answer
43 views

Benefits and Drawbacks of Swapping Associations of Positivity and Negativity of the Proton and Electron

For historical reasons, I understand that a proton's charge was assigned the label of "positive", the electron's charge was assigned the label of negative, and, crucially, equations of current in E &...
4
votes
4answers
226 views

Is anything lost by simply saying that a charge is nothing but the divergence of a field?

If we propose that 1) there are fields and 2) that some fields can have places where they converge (that is to say, places where del dot the field is not zero) then we have the definition of such a ...
1
vote
1answer
67 views

Confusion on negative charges, current, and direction

My text book seems to have two contradictory statements about the same subject. Under the electrical potential and capacitance chapter, it says that negative charges move from lower to higher ...
0
votes
3answers
102 views

If the speed of electron (in space) is increased, will the magnitude of current also increase? [closed]

Electrons are emitted by a hot filament and are accelerated by an electric field, as shown in the figure. The two stops at the left ensure that the electron beam has a uniform cross-section. (a) ...
0
votes
1answer
83 views

Charges redistribution in Conducting Plates

Lets Suppose there is Conducting plate X and charge Q is given to which means +Q/2 and +Q/2 on each side . Now lets suppose plate Y (uncharged at first) (exactly similar to plate X (area and material ...
1
vote
3answers
71 views

Electric field generated by a small object

I've just begun to study electrostatics and I've read the coulomb law, it describes the electric field generated by a point charge as characterized by a spherical shape. I think it is due to the fact ...
0
votes
3answers
776 views

Energy of parallel plate capacitor

Energy of parallel plate capacitor is defined as $$\frac{CV^2}{2}$$ where V is the potential difference between plates, but shouldnt we need to find the potential energy of each plate due to charge ...
1
vote
1answer
48 views

Why is it so that some of the paper pieces get stuck to it while others drop instantly when they stick?

When we rub a comb on our head and held it near pieces of paper then they get attracted because of induced opposite charge.
0
votes
0answers
36 views

Conductance Charged Box

A box with thick and conductive sides with dimensions: Lx, Ly, Lz- while LZ>>Lx,Ly. The long dimension of the box [Lz] can be viewed as infinite so Phi(x,y,z)=Phi(x,y) Given that: Phi(0,y)=-Phi(Lx,...
1
vote
0answers
104 views

Why is the $\vec E$ field inside a sphere = 0? [closed]

I was taught Electric Field inside a sphere is 0, because of Gauss Law. But inside a uniformly charged sphere, if I go at a distance of $r$ from the centre, I will be closer to the +ve charge and ...
1
vote
1answer
115 views

Should the electrical charge of $\pi^+$ (positive pion) be considered exact?

According to https://en.wikipedia.org/wiki/Elementary_charge, IIUC, electrical charge of an electron should be considered an exact value of 1.602176634 coulombs instead of an experimental value with ...
0
votes
1answer
219 views

Change in potential energy of a parallel plate capacitor as a dielectric slab is moved in the space between plates

I was doing this question: If a parallel plate capacitor made of square plates of side L and separation D is connected to voltage source V. And then a dielectric slab of width D is introduced ...
0
votes
1answer
75 views

How do surfaces charges accumulate?

When a voltage source is applied across an ideal wire, do the push of electric field of battery source causes the accumulation of charges on the surface of wire or the capacitance of wire causes it? ...
0
votes
1answer
46 views

Electric potential / infinity is not the 0 reference

Let's say we have a charged sphere with radius $r$. Usually, the way we define its potential is $V = kQ/r$. In this way, we have defined its potential with infinity as the zero reference point. Let's ...
0
votes
1answer
55 views

Why charges should go to the surface of conductor? [duplicate]

How can we show that charges should go to the surface of a conductor, assuming that system should minimize its energy? (With no additional assumptions and maybe using variation method!)
0
votes
1answer
42 views

Polarized Vs Non-Polarized Capacitors

I am wondering what makes a polarized capacitor physically different than a non-polarized capacitor. I am aware they are functionally different. I understand the physics of a non-polarized capacitor, ...
1
vote
1answer
66 views

Do $\rho$ and $\vec j$ change in a moving frame?

Consider a cylindrical symmetrical infinite wire with radius $R$. The wire has constant charge density $\rho$ and current density $\vec j$ (pointing to the right). This is measured from the stationary ...
-3
votes
1answer
193 views

Which is more fundamental property of matter: charge or mass? [closed]

I haven't got a whole satisfying answer to this question. I think that matter can exist without charge but it can't exist without mass. Am I correct? So this fact may be answered by asking about the ...
2
votes
0answers
77 views

BRST Charge in QED

The pure gauge QED Lagrangian density, including the ghost fields, is \begin{align*} \mathcal{L}=-\frac{1}{4}F^{\mu\nu}F_{\mu\nu}-\frac{1}{2\xi}(\partial^\mu A_\mu)^2+\partial^\mu\overline{c}\...
0
votes
0answers
30 views

Charge placed asymmetrically inside a cavity in a sphere (conducting)

The question was something like this -> If I have a charge kept inside a cavity made in a sphere of radius $R$ and the radius of the cavity is $r $ where $(r<R)$. Now I do not keep the charge $q$ ...
0
votes
1answer
48 views

Charge distribution in a sphere in uniform field

So my teacher was telling about how if we place an uncharged conducting sphere inside a uniform electric field , the charges so distribute that the E field inside them becomes zero. He told us that ...
1
vote
2answers
172 views

Violation of the Law of Conservation of Charge in black hole? [duplicate]

Hey I'm a noob to physics however after reading about black holes and Hawking radiation. If a black hole made entirely out of negatively charged particles (say this black hole is made entirely of ...
0
votes
2answers
32 views

Equipotentiality of the conductor surface with extra charges sprinkled and Poisson's equation

The electrostatic potential $\phi(x,y,z)$ everywhere on the surface of a conductor/metal is the same. For a quick reference see this post. Hence, any derivative of $\phi(x,y,z)$ must be zero on the ...
0
votes
1answer
58 views

The force involved in magnetic attraction

Magnetic field causes a force to act on moving charges as in this equation: $F = qv*B$. So what is the force that causes a magnet to attract a charge-less piece of iron? or causes the like poles of ...
3
votes
3answers
346 views

Why are there $1 / 1.602176634 \times 10^{-19}$ electrons in a coulomb?

Why that exact number of electrons in one coulomb? who decided it? there is nothing wrong with the number, it just seems slightly messy. Why didn't the scientific community just settle on an easier ...
1
vote
1answer
89 views

What physical quantity remains equal in different frames? [closed]

I recently came across a problem which involved going into rotating frames. And it was pretty tiring. (And difficult..). So I wondered if there was some quantity that you could measure from the ground ...
2
votes
3answers
140 views

Does a moving charge interact with the magnetic field it produces? [duplicate]

So the title cuts my question a bit short. If a moving point charge produces a magnetic field, does the magnetic field it produces affect it? And let's suppose a moving charge is moving in a region ...
0
votes
1answer
153 views

How to take the derivative of potential?

The electric potential $\psi$ at a point inside the volume charge distribution is: $$\displaystyle \psi = \lim\limits_{\delta \to 0} \int_{V'-\delta} \rho'\ \dfrac{1}{|\mathbf{r}-\mathbf{r'}|} dV'.$$ ...
1
vote
0answers
50 views

How shall we show the surface integral approaches a limit (or does not blow up) at a field point near $S'$

Consider the electric field due to volume charge distribution in volume $V'$: $\mathbf{E}=\displaystyle \int_{V'} \rho' \dfrac{\mathbf{r}-\mathbf{r'}}{|\mathbf{r}-\mathbf{r'}|^3} dV'$ The integrand ...
0
votes
1answer
62 views

Can we use Gaussian pillbox method to determine electric field at a point just near the surface of a surface charge distribution?

I know we can use Gaussian pillbox method to find the discontinuity at the surface of a surface charge distribution. But can we use Gaussian pillbox method to determine electric field at a point just ...
0
votes
0answers
30 views

Is there a direct evidence for the fact that quarks have fractional charge? [duplicate]

Is there an evidence for quarks having fractional charge? Besides the fact that we know there must be 3 of them inside the nucleons, and the only way that this could happen is if they have indeed ...
0
votes
2answers
71 views

Work done by battery in moving charge $Q$ in circuit

why work done by a battery in circuit is potential diffrence across plates times charge flown through body. W=Qε(ε is emf of battery) although there are heat and other loses ? and another that my ...
0
votes
1answer
66 views

Charges on conductor

So i was reading an answer to question Why are the two outer charge densities on a system of parallel charged plates identical? Points that I didn't understand that how come -Q1+x charge can get ...
0
votes
2answers
41 views

How to fix a charge

How do we fix a charge (positive or negative) in a given position in electrostatics? I know that we assume that we fix a charge by some unspecified force, but what are they? Please explain with some ...
0
votes
1answer
76 views

What is the radius of the helix a charged particle makes when entering a magnetic field at an angle?

Here is the equation I found in my textbook but it doesn't make sense: $R=\frac{mv\sin α}{QB}$ . Looking at this formula we can say that particle A moving through magnetic field at an angle $α<β$ ...
0
votes
2answers
141 views

Is it true that any electrostatic charge density can be represented by Dirac Delta function? Give me a general example

My college professor said that any charge density can be replaced by Dirac Delta function but how I want to know.
0
votes
1answer
13 views

Effect of the magnetic field of a moving charge on the magnetic field used to accelerate the charge

Ok, so my brief understanding is that an accelerating charge will produce a magnetic field. If the charged particle, say an electron is being accelerated by a magnetic field, how does the electron’s ...
0
votes
3answers
89 views

How to figure out whether a force mediator is $W^+$ or $W^-$ in Feynman diagram?

How to figure out whether a force mediator is w+ or w- in feynman diagram? I always make sure each vertex is zero but sometimes I get my w+ or w- worng.
1
vote
4answers
186 views

Confusion about electron flow and current

So, I learned in class that current is defined as positive charges moving from south to north. However, in all reality, the negative charges are moving, but the convention of positive to negative wors ...
0
votes
2answers
377 views

Interaction of an electric field of infinite length [closed]

Question: In a system which prodivides an electric field of an infinite length, if another electric field or particle interacts with it at a certain point, will there be a change at a point infinitely ...
3
votes
5answers
854 views

Isn't Kirchhoff's junction law a violation of conservation of charge?

As a beginner of classical electrodynamics I am quite confused in understanding Kirchhoff's junction law or it may be the reason that I misunderstood the law of conservation of charge.Please correct ...
1
vote
1answer
93 views

Energy density in electrostatics - definition [closed]

Background: It can be shown that the potential energy of charge distribution can be calculated by $U = \frac{1}{2}\int_V \rho(r')\Phi(r') d^3r' $ by means of integration by parts and the poisson ...

1
6 7
8
9 10
40