Questions tagged [charge]

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

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3answers
344 views

Electric Field vs Distance (Contradiction)

There was a text book question in my physics class this morning on what happens to the strength of an electric field $E$, if its distance between two plates decreases by 2 fold. My initial thought ...
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0answers
39 views

Infinite charge distribution [duplicate]

I've been thinking about a distribution of charge that does not follow Maxwell's euations, and I can't understand what's wrong with my reasoning. If we have a constant distribution of charge $\rho(x,y,...
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1answer
34 views

Charge in a conductor

How to measure net charge flowing through a current-carrying conductor or a wire without actually measuring the current?
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1answer
63 views

Conflicting models about how energy transferred in an electric circuit [duplicate]

I've been studying DC circuits recently, but I've run into some confusion concerning how batteries deliver energy to circuit elements. From what I've read online, it seems that energy in circuits ...
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2answers
133 views

Common potential in Capacitors

If two isolated charged capacitors (of different capacitance) are connected in parallel to each other they acquire a common potential. But suppose if i connect positive plate of one capacitor to ...
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3answers
219 views

Charging electroscope

In above picture. When near positive rod to the electroscope, electrons go to top of electroscope. then connect electroscope to ground. Why electrons go from ground to electroscope? in top of ...
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3answers
56 views

Would fast oscillating charged object emit light?

If I were able to mechanically oscillate an electrically charged object at frequencies of 430-580 THz, would the object emit light?
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2answers
95 views

Charging sphere with induction

In the above picture, when we connect the positive side or negative side of the sphere to ground, electrons go to ground. Why isn't there any difference between the situations when the negative side ...
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5answers
3k views

How can the electric potential be zero at a point where the electric field isn't, if that field can give a test charge kinetic energy?

Say we have 2 charges set up like above. Why is $V_3=0$ ? I can understand mathematically that the scalars fields cancel out, but I don't understand it physically. If I place a positive charge in ...
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0answers
80 views

Are there compelling reasons not to organize the elementary particles by charge and spin? [closed]

I don't like the way the standard model is currently displayed (see second picture for reference). It does a poor job of abstracting the information into something understandable. As far as I ...
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1answer
41 views

Effect of a current carrying wire on a point charge

Given a point charge $q$ near a wire carrying current as shown, what would be the effect of the magnetic field produced by the wire on this point charge $q$? I think the sign on $q$ is important so ...
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1answer
198 views

Why do bound charges not appear in boundary conditions on a surface between two dielectrics?

I'm studying electromagnetism, more specifically dielectrics. However, the concepts of bound charge and free charge have been somewhat confusing for me yet. The Griffiths' book deduces one of the ...
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1answer
19 views

Charge in the middle of a flat dielectric

We know that due to external uniform fields, the dielectric atoms get polarized in the direction of the field, but what if the charge is inside the dielectric, the electric field of the charge is ...
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1answer
68 views

Does a metal with a strong positive charge decrease its strength?

Does a metal with a strong positive charge decrease its strength? According to the mainstream theory of metal bonds, free electrons form a link between lattices. If this is the case, the removal of ...
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1answer
61 views

Electric field in a circuit

The electric field is defined mathematically as a vector field that associates to each point in space the (electrostatic or Coulomb) force per unit of charge exerted on an infinitesimal positive test ...
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0answers
35 views

How much color charge does a quark carry? [duplicate]

If we look at QED, we can say that an electron carries the charge $$Q_\text{electr.}=-e = -1.602\cdot 10^{-19}\text{ C}$$ so how can we extend this to quarks? Would, for instance, $$ Q_\text{red} = ...
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1answer
52 views

Electric field between capacitor plates

When we try to find the electric field between the capacitor plates, what is the right way to do it? This is one of the ways I've seen and I don't understand why: Using a Gaussian cylinder on the ...
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2answers
97 views

Applying Gauss's law on a disc

Shouldn't the electric flux through a circular disc due to a point charge kept at some finite distance from it be zero as all field lines which enter it exit it also and hence the net would be zero?
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2answers
180 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 ...
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0answers
53 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 ...
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1answer
45 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
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1answer
123 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
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1answer
68 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.
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2answers
82 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 ...
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3answers
242 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 ...
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1answer
300 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 ...
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1answer
37 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 &...
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4answers
220 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 ...
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1answer
65 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 ...
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3answers
82 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) ...
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1answer
69 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 ...
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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 ...
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3answers
302 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 ...
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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.
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0answers
34 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,...
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0answers
101 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 ...
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1answer
103 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 ...
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1answer
118 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 ...
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1answer
63 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? ...
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1answer
40 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 ...
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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!)
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1answer
35 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, ...
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1answer
57 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 ...
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1answer
156 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 ...
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0answers
61 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}\...
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25 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 $q$ ...
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1answer
46 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 ...
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2answers
31 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 ...
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1answer
52 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 ...
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3answers
291 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 ...

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