Questions tagged [charge]

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

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Question about the potential energy of a charge

If I place a book on a shelf in a gravitational field, the book will of course continuously exert a force on the bookshelf. If I place a small charge above a barrier in an electrostatic field ...
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Can a magnet deflect a static charge? If not, how do photons work?

A moving magnet is supposed to generate an electric field. That implies that a moving magnet should be able to deflect a static charge. Will the charge be deflected? If it does not deflect a static ...
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Elemental electric charge without rest mass

Does the non-existence of an elemental electric charge without associated rest mass suggest that atleast a part of the definition of electric charge is dependent on that of mass? I have read from the ...
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Can we charge a ray of light? Can photons never be charged under any circumstances? [closed]

can quantum theory never explain the hypothetical phenomena of charging photons? were there any experiments in this feild?
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How to find a point between two positive (or negative) charges where a third charge would remain stationary? [closed]

If for example there are two charges 9 and 5 coulombs on a plane a meter apart. How can a point be found where the net force on a test charge would be zero. I understand that all the net forces need ...
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Why is the W boson (and none other elementary boson) the only with EM charge?

I have read this question: Working out the charge of a W Boson The role of W bosons in the weak nuclear force and beta decay The W, Z, together with the photon comprise the four gauge bosons of the ...
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1answer
127 views

Integrating the derivative of a Dirac delta function [closed]

I need to prove that $\rho=p_0{d\over dx}\delta(r-r_0)$ is the charge density of a single electric dipole in the point $r_0$ which direction is the $x$ axis. for that i should find the charge , dipole ...
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Two protons inside a negative sphere [closed]

Problem: Imagine a sphere of radius a filled with a negative charge density equal of two electron charge. Embedded in this is two protons, assume that the negative charge distribution remains uniform ...
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Why is the Higgs boson chargeless

Well, I know if this question was asked about another particle the answer would be that the charge of a particle in an intrinsic property and that’s that(as far as we currently know), and that might ...
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Faraday Cage Explain (Gauss Law)

I was given the following explanation of Faraday cage: There is no electric field inside a hollow, charged conducting shell because a Gaussian surface inside the shell must have zero flux through it ...
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Energy consideration and charge flow in an RC circuit

Okay, so I know that a capacitor is charged by the battery providing a potential difference which forces positive charge to flow from one capacitor plate to the other (Conventional Flow). This flow of ...
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Contradiction about the direction of magnetic force

I have encountered two contradictory directions for the force felt by current in a wire immersed in a uniform magnetic field. Halliday says the force should be to the left in the situation pictured ...
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How was charge controlled for early experiments?

One of the first topics usually taught in electrostatics is Coulomb's law. I understand that he measured the relationship between charge and distance using a torsion balance. My question is, how was ...
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Switching the position of voltage probes changes the sign of the measured voltage. How can you determine the charge sign in a Hall effect then?

When you measure the voltage in a battery, for example, you place the voltage probes at the battery ends and get, let's say, a reading of 1.5V. If you change the position of the probes in regards to ...
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Electrostatic potential energy stored in a system of point charges, where to use it? [closed]

I'm approaching the potential of electrostatic field and before that, following my class' program, we prove that electrostatic field is conservative and therefore define the electrostatic potential ...
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Is it true that whatever current enters a battery, also leaves the battery? Why?

How is it true that whatever current enters a battery also leaves the battery? Is it due to one of the Kirchhoff's laws? Can anyone show how that is? How can I reach this conclusion logically/...
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It is said that there is no 'net' motion of charges in electrostatics. What does this 'net' motion mean?

I read in a text book that the electric field on the surface of a conductor must always be perpendicular to the surface or else charges will have net motion. If the field is normal to the surface, ...
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Does stripping electrons from atoms or adding them affect the state of matter in any way?

Does electric charge affect melting, boiling point or sublimation temperature?
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Does electric charge effect boiling point? [duplicate]

Does stripping electrons from atoms or adding them effect the state of matter in any way?
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Trying to define the electrostatic potential of a point charge

I've been trying to define the electrostatic potential (V) for a while now, it's something that I've covered last year and now need to know what exactly it does mean, I came up with this and all I ...
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Electric fields in continuous charge distribution

My question may be very basic, but I can't think of a reasonable explanation for this. Consider a solid charged sphere. Now, we have an electric field inside the solid sphere, but at any particular ...
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1answer
127 views

“Derivation” of continuity equation

The surface integral of j over a surface S, followed by an integral over the time duration t1 to t2, gives the total amount of charge flowing through the surface in that time (t2 − t1): $${\...
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1answer
129 views

Why do we still call the electron charge the elementary (EM) charge?

The electron is an elementary particle, part of the SM, pointlike, with no substructure, or spatial extent. Its intrinsic properties include its EM charge, which we still call the elementary charge. ...
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1answer
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Potential of hydrogen atom solution of the Laplacian: Missing boundary condition to fix integration constant $c_1$

I have following problem, I want to calculate the classical potential $\phi(r)$ of the hydrogen atom in its ground state. The charge density is known: $$\rho(r)=\frac{-e_{0}}{\pi a^3}e^{-\frac{...
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Why are there 6 interactions with 4 positive charges?

From a homework assignment, there are 4 spheres spaced 1cm apart. Each of the spheres are charged to +10nC and weigh 1 gram. The question wants us to find the final speed of the charges once they've ...
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If the cross-sectional area of a wire doubles shouldn't the current also double?

In this question the answer is B but I don't understand how that could be possible considering the area has doubled.
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When to use $e^{-t/RC}$ - Capacitor discharge and charge

Respected Team Members, I am learning how to calculate the amount of time it takes to charge/discharge a capacitor. The Formula given in the text book is $$\ V_{f}=V_{s}(1-e^{-t/RC})$$ But we ...
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Gauss' Law not including all of the system

Suppose we have a system of two parallel conducting plates charges $Q$ and $-Q$ and charge densities $\sigma$ and $-\sigma$. In this case, to find the electric field, Gauss' Law is used with a ...
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Proof of continuity of voltage across a capacitor

It is known that the voltage drop across a capacitor is a continuous function of time. This means that, for each instant t0, we may write: V(t0-) = V(t0+) This relationship is very used in the time ...
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What is the function $q$ in the definition of charge density?

Supposed we define $\lambda = \frac{dq}{dl}$. If I think of this intuitively, this makes sense; the linear charge density at a point is tiny amount of charge at that point divided by the tiny length ...
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Electrostatics, measurement of charge

How did physicists come up with a standard for measuring charge? How an electrical measurement of charge was made?
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Energy of the system of similar charges

We know that two same charges repel each other. To stop the charges from going away we have to exert an external force and hence energy is used. But if in a vacuum two similar charges are placed near ...
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The potential at a point

According to my book, 'The potential at a point is said to be 1 volt when 1 joule of work is done in bringing 1 coulomb charge from infinity to that point.' But I wonder how it is possible. As the ...
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Conservation of Charge vs. Conservation of Energy

Is conservation of charge ever violated like conservation of energy is violated during cosmological expansion? I am trying to understand this with respect to Noether's Theorem.
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If voltage represents an energy difference between two points, why don't electronic appliances all use the same amount of energy?

As I understand it, voltage is an energy difference between two points. $$V_f - V_i = - \int \mathbf{E} \cdot d\mathbf{s}$$ But consider a toaster and a refrigerator each using their own 120V ...
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Gauss law in electrostatics

Consider a solid conductor,if the conductor makes a free electron inside that due to thermal energy ,so that causes one positive ion inside the conductor, my question is according to gauss law inside ...
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$E$ outside a Metal Spherric Shell with a off-center Point Charge inside Shell

If a charge +Q is placed inside a metal shell (NOT at the center), as shown below. I can understand that E will be 0 between inner surface and outer surface due to this is a conductor. Then according ...
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What's the electric field in a sphere with charge $Q$ and an inverse linear/square law density of charge?

In Classical Electrodynamics by Jackson problem 1.4 asks to find the electric field as a function of the radius of a sphere charged with a charge Q and with a spherically symmetric density that goes ...
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Is the centre of charge always within the centre of mass of an object?

What I am confused about is whether the charge of an object is concentrated within the centre of the mass itself, or does it change depending on the situation?
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How do we arrive on the same expression for Gauss's law when deriving it for a sphere or any other figure (say a cylinder)? [closed]

For a circular surface, the surface area of the circle is cancelled by factors in the denominator of $E$, leaving behind only $Q/\epsilon_0$. But what about when we conside a cylinder? How so we ...
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$CP$-transformation for spinor field. $C$ and $P$ do not commute?

I am bothered by an exercise about CP transformations where I get the result that CP acting on a Dirac spinor field is not the same as the PC transformation. The exercise states the following ...
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How to perform integration for all of space?

Two conducting spheres of radii $a$ and $b$ have charges $Q_1$ and $Q_2$. Distance between their centres is $R$. If ${\vec E_1}$ and ${\vec E_2}$ are electric field vectors due to the two spheres at ...
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Can one assume during the discharge of lightning, some energy is dissipated as heat? (High School Physics)

I was doing homework, and the following appeared as a question: A negatively charged thundercloud above Earth's surface may be modeled by a parallel plate capacitor. The lower plate of the ...
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Boundary conditions for an infinite line charge and grounded conducing plane

I'm not asking for a solution to the problem, I'm confused about what I should set the boundary conditions to, it's obvious that $V=0$ at $z=0$ because of the grounded $xy$ plane, but I don't know ...
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Best representation of a proton in non-static spacetimes

The classic way to represent a proton in flat spacetime is to use a simple point charge, $$J = (e \delta(r), 0)$$ But if we're using an arbitrary metric (let's assume still globally hyperbolic ...
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Poisson's equation and electric field interpretation

My question is this: Are all solutions to Poisson's equation for a certain charge density such that the negative gradient of them will give me the electric field? In deriving the equation, we say ...
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On the microscopic description of a steady electric current

In Purcell's Electricity and magnetism, page 137, the author derived a formula describing the average velocity $\overline{\textbf{u}} $ of positive ions inside a conductor, a gas made of neutral ...
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Does Gauss' law simplify even if charge density is dependent on angle?

We know that with Gauss' law applied to a charged sphere simplifies due to the symmetry of the sphere and we can take $E$ outside of the integral, but what if the charge density $ \rho$ depends on ...
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Electric Field Lines between two equal charges end at the midpoint, violate rule that lines only start/end at charge/infinity

At the midpoint of the line joining two equal point charges, the field is zero, and the electric field lines on this line joining the charges each begin at a charge and kind of end at the midpoint. ...
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How can charge reside inside a solid sphere of charge?

I was studying the electric field and potential of a solid sphere of charge. In my textbook it is mentioned that we distribute electric charge in the interior of the sphere. I had learnt that in a ...

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