Questions tagged [charge]

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

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1answer
98 views

Can a third kind of charge exist? [duplicate]

Is it possible that apart from positive and negative charges, there is a third kind of charge that we have somehow, not discovered yet? If not, is there some proof of the existence of only two types ...
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1answer
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Confusion from Griffith's book

In Griffith's Electrodynamics (Third Ed.), on page no. $176$, it is written: It may have appeared to you that I left out the surface bound chrage $\sigma_b$ in deriving Eq. 4.22, and in a sense ...
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Conserved charges without conserved currents?

I recently read (Section 9.3 of J.Kaplan AdS/CFT notes) that we can have QFT's s.t. we have conserved charges but NO associated conserved currents. How is this related to the gauging of global ...
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2answers
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Is the Electric Field defined in a charge density?

If I apply Coulomb's Law, I get that the field is defined in all space for volumetric densities. For linear and surface charges, the field is undefined where the charges are (division by $0$). Why ...
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1answer
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Can one capacitor charge another connected by a single lead only?

My instructor presented the following problem on capacitors: Plates 1, 2, 3, and ...
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1answer
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How to prove $Q_u = -2Q_d$ from $SU(5)$?

I'm a beginner, and I'm trying to figure out how to prove that charge of Up quark is equal to 2 times the charge of down quark from the 10 representation of $SU(5)$. Please help.
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For which reason do we say that the charge surface density is rougly constant (uniform distribution) on a capacitor's plates?

Consider for instance a parallel plate, a spherical or a cylindrical capacitor. Usually we analyze it by considering the surface charge density on each plate uniform, i.e. constant along the plate. ...
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7answers
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Why is electric flux through a cube the same as electric flux through a spherical shell?

If a point charge $q$ is placed inside a cube (at the center), the electric flux comes out to be $q/\varepsilon_0$, which is same as that if the charge $q$ was placed at the center of a spherical ...
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1answer
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Can charging by conduction and charging by induction occur simultaneously?

If I connect a neutral body to a charged body (suppose it is negatively charged) with a conducting wire, how will the neutral body get charged - by induction or by conduction?
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1answer
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Field inside a spherical cavity

A spherical portion has been removed from a solid sphere having a charge distributed uniformly in its volume. If at all a cavity is carved inside the sphere...will the field inside the cavity be equal ...
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1answer
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Gauss's law and electric field inside spheres and shells

I have a question regarding the electric field inside a sphere and shell and I know the result but don't really understand why it is what it is. Lets say there is a shell with radius $R$ and that has ...
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2answers
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Electric field on the surface of an infinite sheet of a perfect electric conductor

let's consider ai infinite and flat sheet of charge distributed on a conductor. Well, it is known that the electric field at steady state on its surface (which is orthogonal to it) is equal to: $\ E =...
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1answer
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Why couldn't Dalton's atomic theory explain the occurence of electricity?

It is said that Dalton's atomic theory was unable to explain results of many experiments,for example, it was known that substances like glass or ebonite when rubbed with silk or fur generate ...
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1answer
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Distribution of charges: parallel plates and potential [closed]

How do you calculate the charge distribution on three parallel plates which have unequal charges on them and then they are connected by a wire? Also, we need to calculate the field and potential ...
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Calculating energy exerted on individual atoms/molecules in a dielectric

If you have a dielectric material with a given dielectric constant (say one in a parallel plate capacitor for simplicity) that is polarized by a given electric field, can you calculate the effective ...
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2answers
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Which is the best method to solve electrostatic problems? [closed]

let's consider a certain space volume in which there is a certain charge distribution $\ \rho(\vec{r}')$ (suppose at the moment that we know it). Suppose you want to find the electrostatic potential $...
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Would a person’s hair stand if they were in an electrostatically charged inside a plastic bag?

I don’t have an access to Van der Graff generator to test this and was curious whether the charged hair of a person touching high voltage electrostatic generator would stand (remain charged) inside a ...
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1answer
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Charge Density as a function of the Electric Field

A ball with radius $R$ has a non-uniform charge density $\rho(r)$. The electric field of the ball as a function of position $E(r)$ is known. How would you then find $\rho(r)$? I was thinking that, by ...
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Influence in Beaker Electroscope

In WDemtröder's book Electrodynamics and Optics there is an experiment, which involves: a) charging a conducting cup by touching the inner cup wall with a charged ball b) charging a conducting cup ...
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1answer
91 views

How much work is done by bringing two positively charged rods together? [closed]

We have two positively charged rods placed far apart. First rod has a charge $e_1$ and length $L_1$, second has a charge $e_2$ and length $L_2$. How much work is done, when we push them closer to a ...
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3answers
287 views

What would be the electric field lines for parallel plates with different charge density?

How would electric field lines look like if charge densities on parallel plates (like the ones used in parallel plate capacitors) are different (still opposite though so electric fields can form)?
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3answers
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Does the centre of charge behave as a point charge?

We can find the centre of charge of a system of charges in much the same way we find the centre of mass of a system of masses Suppose we have two charges of the same polarity and equal in magnitude ...
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Can a massless object have a charge associated with it? [duplicate]

So I've been stuck with this thought for a few days and have not been able to find an answer which can clear this doubt. Is it necessary for an object to have certain mass associated with it if it ...
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1answer
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Calculating electric field at an uncharged portion in an otherwise uniformly charged sphere

We were doing some problems on electric fields and my teacher discussed this one : Prerequisite: The electric field at a radial distance r inside a uniformly charged sphere of charge density ρ is ...
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What is the force between a charge and a dielectric (polarized in the presence of charge)?

We know the reason why a charged balloon will get attracted to the wall is because of polarization. But how can we calculate the force between the polerized dielectric and a charge depending upon: ...
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1answer
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What if I insert more charge into a charged capacitor?

Suppose we have a charged capacitor with charge = $Q_1$ and then an electron beam inside the positive plate of the capacitor. The electrons entering the positive plate are repelled by the negative ...
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2answers
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What is the meaning of the term “referenced” as in referenced to ground?

This is just something I have been obsessing with today. I work in the commercial/industrial electrical field and often involved in training apprentices. Several places in the curriculum the texts ...
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1answer
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Why does the electrostatic potential energy decrease when we connect two charged conductors?

When two conducting spherical shells are connected by a conducting wire, electrons replace themselves until the electric potential of both shells is identical, that much is understood. What I don't ...
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Dielectric material and capacitor

First, If something is unclear because of my English, let me know. Assume I have a two-board capacitor connected to a power supply which delievers constant voltage value,and I am willing to fill it ...
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3answers
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How fast is electrostatic force? [closed]

Suppose we have a charge $Q$ in deep space (isolated), now suppose another charge $q$ appears instantly (no matter how). Obviously it will feel electrostatic force but the question is how quickly (...
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The relative motion of a charged particle moving through a magnetic field

When a charged particle moves in a magnetic field, a force of $F=qv\times B $ is applied on the particle. (Lorentz force) So lets say that a magnet is sitting on a table, and a charged particle is ...
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Electric field at some distance(a) from charged particles arranged in a straight line?

I know that there are derivations of charged infinite wire and we can get the total electric field by integrating over the whole wire. but if now we imagine that the wire is not continuous instead ...
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1answer
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If a charge comes into existence, and there is another charge 20 light years away(which existed for eternity), what will be the interaction?

Our physics teacher just taught us a bit about electric fields, and why the concept was invented. He said that if a charge comes into existence, another charge won’t feel its effect instantaneously, ...
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Electrostatics Charges in Stable or Unstable Equilibrium or Numerical - How to solve this analytically?

In this problem we can have a negative charge to the Right of +q and Positive Charge to the left of -3q for the Purpose of equilibrium of all the Three Charges. Now we know that for stable Equilibrium ...
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1answer
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Physical meaning of Debye length

In plasma physics, what Debye length should represent in practice? From what I understood it's the maximum characteristic distance within which separate charges can be present in the internal space ...
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1answer
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How to minimise sum potential of the system?

Given $m$ number of immobile electric charges at some points of the plane. We want to place $n$ number of further charged particles (not including the fixed charges) along a circle centered at the ...
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1answer
36 views

Why does a battery voltage depend on its state of charge?

I know that measuring the open-circuit voltage gives a good indication of the state of charge of a battery, both for rechargeables and single-use. But why is this so? As far as I can see the voltage ...
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1answer
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Looking for help justifying a factor of $1/2$ in Jackson's formulation of electrostatic energy in dielectric media

Electrostatic Energy in Dielectric Media In Section 1.11 we discussed the energy of a system of charges in free space. The result obtained there, $$W=\frac{1}{2}\int \rho(\mathbf{x})\Phi(\...
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2answers
38 views

Even though the field becomes infinite near the charge a gaussian surface can pass through the continuous charge distribution. How? [duplicate]

Even though the field becomes infinite near the charge a gaussian surface can pass through the continuous charge distribution and have a finite value of flux. How?
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1answer
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Can a conductor be uniformly charged?

I have been reading in books that charges on a conductor resides on its surface and that for a body to be uniformly charged it has to be an insulator.Is it true?If yes does it mean we can consider a ...
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4answers
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Using Gauss's law when point charges lie exactly on the Gaussian surface

Suppose you place a point charge $+Q$ at the corner of an imaginary cube. Since electric field lines are radial, there is no flux through the three adjacent (adjacent to the charge) sides of the cube....
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1answer
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Can we transfer the whole charge of a body to another body?

Today my colleague said: "If charged body (say 5 Coulomb) is any charged conductor $A$, it can be done by enclosing $A$ completely by second uncharged conductor $B$ and connecting them by a ...
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2answers
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How can we make a spherical shell uniformly charged?

Today, I was studying Newton's shell theorem (ellectrostatics). There we considered a spherical shell of uniform surface charge density. Then a question popped out in my mind: How can we make the ...
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How does grounding a part of the circuit affect the surface charge?

Recently I stumbled upon the concept of surface charge in a electrical circuit. I found all the information I needed regarding what happens to the charges at the micro scale (equilibrium, transient, ...
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1answer
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Do charges' sign are conventional? [duplicate]

As we know in the universe there are two types of charges, positive for some elementary particles and negative for other. By inversion charge sign of elementary particles the world be the same this ...
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1answer
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Electrostatic induction problem

I am new to electric physics. Now I have a problem about electric induction. In many books I have seen that you can make a conductive sphere positively charged by doing following steps: Hold a ...
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0answers
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Does the separation between two charges change or remain constant when another charged particle is placed at a point where net electric field is zero?

When we place a charge $C$ between two charged particles $A$ and $B$, at a point the force experienced by that charge $C$ is zero. Is the converse also true, that the other two charges also don't ...
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0answers
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Charge density of a point charge [duplicate]

Is it right to say that the charge density of a point charge is infinity? if I were to take a uniformly charged ball with radius R and take the limit $R\to 0$, won't I get an infinite charge density ...
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2answers
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How to calculate the electric field outside an infinitely long conducting cylinder with surface charge density σ

I'm currently studying electromagnetism, specifically Gauss's Law, and have been presented with the following question: Consider an infinitely long cylinder of radius R made out of a conducting ...
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1answer
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A static positive charge in a uniform magnetic field watching by an observer moving at a constant speed

As the picture above, there is a uniform magnetic field from back to front. Put a positive charge in (x,y). Then there is an observer moving along the y-axis at a constant speed(v). Does it seem that ...

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