Questions tagged [electric-fields]

For questions that utilize the concept of electric fields (commonly denoted by the letter E), or for questions whose answers likely involve electric fields. More specific than the [electricity] tag, as questions about the phenomenon & theory of electricity do not necessarily involve the discussion of fields.

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19 views

Electrostatic Potential using Poisson equation

I'm stuck in the following problem. Having in mind an electrochemical transistor, the situation that we consider is a one dimensional electrolyte with non-uniform concentration of ions (with charge q)....
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51 views

Can Gauss' Law apply to an irregular 3D region?

Let's say I have this configuration: The figure above is a cube with a charge not in the center. Can I calculate the flux through the surfaces using Gauss' Law, or does it only apply when the charge ...
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Besides the curl is there any other difference between an electric flux line and a magnetic flux line?

As far as I know, both types of flux mediating the electromagnetic phenomenon and related forces consist of coherent streams of virtual photons according to the known theory. Besides the total non-...
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In the statement $\text dV = 4\pi x^2\text dx$ , how is the radius $x^2\text dx$?

I was recently studying a question based on Electrostatics. Here is the link to the question (along with the answer below). I haven't learned integration yet. But my question here is how did we get $x^...
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64 views

How much energy is stored in the field of a hydrogen atom?

How much energy is in the electric field of a single lone hydrogen atom that has no neutrons and exists at the lowest energy state possible? Well in a universe where nothing else exists.
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51 views

Why is the work through the element the same as the potential difference if we define potential difference this way?(lumped elements)

In the Feynman Lectures on Physics part ||, chapter 22-3 he defines potential differnce like this: The picture is an element in a curicuit, the black lines on top and the bottom are the conductors, ...
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1answer
41 views

Deriving Kirchoffs voltage law using the lumped element model

I have one question about Kirchoffs laws using the lumped element model: https://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws The proof is on the Wikipedia page. They say "Approximate the ...
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1answer
51 views

Electric Potential for a Point Charge and an Infinite Conducting Plane on the Other Half-Space

In the book titled "Modern Electrodynamics" by Zangwill, on chapter 8, there is a discussion on the electric potential of a system of an infinite conducting plane and a point charge ...
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Calculating electric potential from electric field [closed]

The Electric field in a region is given as $\vec{E}=-2x\hat{i}+3y^2\hat{j}-4z^3\hat{k}$. Calculate the electric potential at point $(1,2,3)m$ Now we know that electric potential at point $A$ is ...
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1answer
16 views

Ensemble average of polarization with applied field

This question is in regard to a dipole moment fluctuation formula seen in: MOLECULAR PHYSICS, 1983, VOL. 50, NO. 4, 841-858, on page 843. For a system of polar liquid (water) at equilibrium, the ...
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Why does the voltage goes away in my leyden jar?

This question is similar to this one in the sense that I have my amateurish Leyden jar and I'm supplying ~7.5v from 5 batteries (~1.5v each) in series. Some details and facts after experimenting: ...
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How does zero electric field look like?

Imagine if we have an electric dipole inside a cube (a conductor). The net electric charge inside the cube is zero. Hence, using Gauss's law, the net electric flux coming out of the cube must be zero. ...
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1answer
59 views

Why do alpha particles get deflected by gold foil even though net electric field inside a metal is zero?

The electric field in metal is zero in electrostatics. But in the Rutherford gold foil experiment, alpha particles get deflected from the gold foil showing the presence of an electric field there. I ...
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1answer
31 views

How will a taser act when one neither or only the receiver is grounded?

Person $A$ has a taser and person $B$ is being tased. How will the current affect the two people when : Neither $A$ nor $B$ is connected to the ground (earthed) $A$ is earthed, $B$ is not ...
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117 views

Covariant form of the electric field

I'm a bit confused about some expressions about the relativity of the electric field. The usual treatment ($c=1$) defines the four potential $A_\mu$ and $F = dA$ is the anti-symmetric 2-tensor. Then $...
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Does movement of a charged particle in a electric field imply electric potential energy?

A particle at rest with charge $q$ and mass $m$ is placed in the center of a spherical shell with surface charge $-\rho_s$ on the top half and $\rho_s$ on the bottom half (see image). The particle ...
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3answers
135 views

Electrostatic Potential and Field for an Infinite Conducting Plane with Charges on Both Sides

Suppose that we have an infinite conducting plate that occupies the $x-z$ plane. We put 3 point charges $q_1 = Q,\quad q_2 = Q$ and $q_3=2Q$ in the points $(0,a,b),\quad (0,a,-b)$ and $(0,-a,0)$ ...
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What is the electric field strength required to rip apart particles

Water is a polar molecule, one side slightly positive and the other slightly negative. Would it be possible to rip a water molecule apart into hydrogen and oxygen gas using charged parallel plates ...
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2answers
53 views

Do Electrostatic Charges build up at the ends of an Inductor in closed circuit?

I was watching this video from YaleCourses youtube channel. At around 41.00 minutes, the professor introduces the notion of charge buildup at the ends of an Inductor in a closed circuit. Is the ...
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2answers
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Why does electron stop accelerating after passing anode in Cathode ray experiment?

This same question was posted on quora and what I found out there that there is some graphite coating around the anode extending to just before the florescent material. This graphite coating is ...
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1answer
68 views

What keeps a light wave 'waving'? [closed]

Why does the a light wave crest, rather than continuing off in the direction it's heading prior to the moment it begins cresting? What force/acceleration/thing 'turns' the wave towards the bottom (or ...
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1answer
68 views

Electric field in a rod rotating in a magnetic field [closed]

Recently I came across a problem: A metal rod of length $L$, connected to a vertical shaft is rotating in a horizontal plane with a constant angular velocity $\omega$ (anticlockwise as seen from ...
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1answer
28 views

How does current behave in a piezoelectric circuit?

I am trying to understand the fundamental principles of piezoelectrics, but my searches haven't helped me answer this question. As I understand it, squeezing a piezoelectric causes a mechanical ...
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1answer
55 views

What is the electric field at a distance $r$ due to an infinitely long wire carrying a constant current $I$?

We know that an electric field in terms of potentials is given by $\overrightarrow{E}=-\overrightarrow{\nabla }\phi -\dfrac{\partial \overrightarrow{A}}{\partial t}$. But I just came across, while ...
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How to argue that the potential is the same in a conductor with zero resistance when we have electricity?

I am wondering how we can argue that the electrical potential is the same in point A and B in the figure below: I have seen the argument that in a conductor where the charges are not moving, then the ...
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Charging a metal by extracting electrons from it? [duplicate]

Suppose we have a field emission electron gun as shown in the figure, (let's ignore the voltage of the second anode), the voltage of the first anode is to extract electrons from the cathode, there is ...
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99 views

Why is there an electrostatic field in a closed current?

There is something about the derivation of the formula for parallel resistors I can not understand($1/R_t=1/R_1+\cdots+1/R_N$). In order to derive this formula we use that the potential is the same ...
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41 views

Electric displacement - why are field lines continuous?

I recently attempted problem 4.17 in Griffiths's "Introduction to Electrodynamics" 3rd edition in which you are asked to make a sketch of the electric displacement vector D in and around a ...
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1answer
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In applications where heating is not the required from of energy, current is to be kept low as per Joules law. What energy is considered useful?

As per this paragraph from Wikipedia "Joule heating is referred to as ohmic heating or resistive heating because of its relationship to Ohm's Law. It forms the basis for the large number of ...
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44 views

Does the fields of any other fundamental force beside electromagnetism display duality?

I've always found the duality of the electromagnetic force intriguing: Why does it seem to have two distinct facets in the static case, with Lorentz transformations transforming one field into another,...
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1answer
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Eletric field inside of a conductive charged spherical shell, which has an inner conductive sphere [closed]

Suppose a charged spherical shell, centered at the origin, with outer radius of $R_0$ and inner radius of $R_i$, and it has charge $Q$. Inside the shell, there is a conductive sphere with charge $q$ ...
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1answer
36 views

Electrostatic potential resolving singularity

I'm trying to determine the electrostatic potential caused by a specified charge density function: $$ \rho_c(\vec{r}) =\begin{cases} 1 & \vec{r} \in V\\ 0 & \text{otherwise} \end{cases} $$ The ...
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What exactly does the line integral of an electric field over a closed loop find?

For a conservative electric field, we can always say that $$\oint \vec E\cdot\vec {dl} = 0$$ Take this scenario for example Here $E_1$ and $E_2$ are two different electric fields. If I find $\oint \...
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Is there any kind of "radar" system That can detect electrical fields / electricity

I may be using improper terms here, but Is there any kind of "radar" / non-contact system That can detect electrical fields / electricity? see fig for clarification to what I'm talking about....
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208 views

Direction of electric field at points on boundary between two dieletrics

I am ripping my hairs trying to understand this answer, it is written that, for the following set up of two capacitor plates separated by distance $d$ and area $A$ with three dielectrics insert with ...
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25 views

Direction of induced electric field lines in the following case

I'm a high school student and not that familiar with vector calculus. In my textbook there's a line that says induced electric field lines can form closed loops and the diagram beside it shows a coil ...
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1answer
30 views

How to interpret glow/corona/arc discharge IV diagram?

There's a current/voltage graph on wikipedia for glow discharge that I don't understand. Aren't we driving the voltage? How can the line possibly go down on the voltage axis i.e. have two values of ...
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1answer
61 views

Shouldn’t the electric field inside a slab of charge be zero?

In one of the problems involving Gauss’s law, we have to calculate the electric field outside and inside a symmetric slab of some thickness and certain net charge. Of course, the electric field we get ...
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2answers
80 views

Fourier decomposition of the field into plane waves [QFT]

I am going through the text Quantum Field Theory and the Standard Model and have a question regarding a formula used in chapter 2 on the general solution to the differential equation: $\left(\partial_{...
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26 views

Does Electric Flux Density due to an external Electric field increase in a dielectric medium as compared to free space?

There is exactly the same question on StackExchange but I don't find it rigorous or even right per se. How flux density increases in the dielectric medium? In the 7th edition of the book "...
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1answer
58 views

Electric potential and field lines

I have learned that electric field lines goes from higher potential to lower potential. First of all, how does this happen? And if the above is the case then suppose I have two uniformly positively ...
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31 views

How can I find out the electric field in the parallel to the axis of the ring or disc?

In case of ring, at the axis $\ldots$ electric field is $E=kQx/(R^2+x^2)^{\tfrac 32}$ when we assume constant charge density and distance of the point on axis at a distance from centre is $x$. Now my ...
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3answers
63 views

How does the act of bringing poles closer together increase electromagnetic strength?

According to my textbook, the strength of a horseshoe electromagnet can be increased in the following ways: Increasing the amount of current flowing Increasing the number of turns of the coil ...
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How do dielectric molecules in a liquid phase align when polarized?

As seen in the diagram, when a dielectric material becomes electrically polarized, the molecules align themselves in a manner where the respective charges are parallel to each other horizontally. ...
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1answer
101 views

Does electric field really exist or it is just an interpretation? [duplicate]

Did physicist create the concept of electric field to describe the interaction of charge particles at a distance? If they are real, do we have experimental evidence? Please describe some of them. And ...
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Electric field for material with different dielectric constant

I was reading some papers where people calculate the electric field of charges sitting at the interface between two different mediums, with different dielectric constants, $\epsilon$ and $\epsilon_{...
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1answer
48 views

Rationale for the Electrostatic Field

This is from div grad curl and all that, h.m. schey. By trivial the author, I think, just means dividing the electrostatic force by the test charge to get the electrostatic field. What I need are ...
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1answer
63 views

Please help me understand the nature of electricity and particle behavior

I am trying to understand how electricity works on quantum level. Precisely how is energy actually transferred from generator to the consumer. Here is what I managed to understand so far by reading ...
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2answers
85 views

Are moving charges and changing electric fields different causes?

Question Are moving charges and time-varying electric fields really distinct causes of magnetic fields?? Various EM Phenomena Two larger purposes are providing some Background to make sure I follow ...
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1answer
49 views

Charge distribution in a neutral conductor

I have read and understood that if you give charge to a conductor, the charge comes on the surface of the conductor in electrostatic condition. But sometimes I get confused that whether the case is ...

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