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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 [tag:electricity], as questions about the phenomenon & theory of electricity do not necessarily involve the discussion ...

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Applied Electric Field

Two parallel-plate vacuum capacitors have plate spacings d1 and d2 and equal plate areas A. Show that when the capacitors are connected in series, the equivalent capacitance is the same as for a ...
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Each square centimeter of the surface of an infinite plane sheet of paper has 2.50 x 106 excess electrons [on hold]

Each square centimeter of the surface of an infinite plane sheet of paper has 2.50 x 106 excess electrons. Find the magnitude and direction of the electric field at a point 5.00 cm from the surface of ...
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Electric charge [on hold]

In a physics lecture demonstration in a charge of -0.180 uC is placed on the spherical dome should you sit for the electric field at your location to be within the recommended maximum of 614 N/C. ...
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Measuring the earth's electric field

My question stems from a question on the Dutch VWO-level highschool state exam (from 1993) concerning a device to measure the earth's electric field. It consists of two plates positioned above one ...
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Magnitude and Direction of Electric field [on hold]

Two positive point charges q are placed on the x-axis, one at x=a and one at x=-a. a) Find the magnitude and direction of the electric field at x=0. b) Derive an expression for the electric field at ...
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electric flux relation to gauss law [on hold]

The cube has sides of length L= 10.0 cm. The electric field is uniform, has a magnitude E= 4.00 x10 3 N/C, and is parallel to thexy-plane atan angle 36.9° measured from the +x-axis towards +y-axis. ( ...
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Electro-magnetic field __ [on hold]

Each square centimeter of the surface of an infinite plane sheet of paper has 2.50 x 106 excess electrons. What is the magnitude and direction of the electric field if it is 5.00 cm from the surface ...
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The potassium chloride molecule (KCL) has a dipole moment [on hold]

The potassium chloride molecule (KCL) has a dipole moment of 8.9x〖10〗^(-30)C.m.a) Assuming that this dipole moment arises from two charges ±1.6x〖10〗^(-19)C separated by distance d, calculate d. b) ...
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ELECTRIC FIELD AND ELECTRIC FORCES [on hold]

a.) What must be the charge (sign and magnitude) of a 1.45g particle for it to remain stationary when placed in a downward-directed electric field of magnitude 650N/C? b.) What is the magnitude of ...
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Can a point charge inside a cavity affect the electric field outside the conductor? [on hold]

A solid conductor has a cavity in its interior. Would the presence of a point charge inside the cavity affect the electric field outside the conductor? Why or why not? Would the presence of a point ...
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Electrodynamics : Problem with Notations for fields $\vec{(\vec{r},t)}$ and $\vec{B}(\vec{r},t)$(complex and real notations)

I'm sutyding a course on electrodynamics and am stuck on a few lines I can't make sense of. The professor uses $$\vec{E}(\vec{r},t) = \vec{U_0} cos (\vec{k}\cdot \vec{r} - \omega t + \phi)$$ (so far, ...
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Definite charges [duplicate]

Is it possible to have an arrangement of two point charges separated by a finite distance such that the electric potential energy of the arrangement is the same as if the two charges were infinitely ...
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1answer
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Grounded parallel plate capacitor

What will be the charge distribution if a parallel plate capacitor, which is not connected to any battery, is given charge on one plate(say Q on the left plate) and is grounded on the outer side of ...
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Reaction forces in electrodynamics

Consider two conducting plates, at different potentials so as to set up an electric field. A charged particle is released in the field. The particle experiences a force for sure, but is there a ...
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1answer
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The force that opposes the short circuit terminals from getting separated? [on hold]

if u have observed whenever u short two wires u can experience that sometimes it requires effort to separate those live terminals even if they have not welded but stuck pretty close to one another ...
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Functions unbounded at a point on the domain: How to show electric field exists for any continuous volume charge density?

My understanding after reading Mike Stone's answer: \begin{align} \vec{E} &= k \iiint_{V} \dfrac{\rho(x',y',z')[x-x'\hat{(i)}+y-y'\hat{(j)}+z-z'\hat{(k)}]}{[(x-x')^{2}+(y-y')^{2}+(z-z')^{2}]^{...
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Why are magnetics fields recorded by MEGs (magnetoencephalograms) not distorted by the scalp?

My question "Why are magnetics fields recorded by MEGs (magnetoencephalograms) not distorted by the scalp?" arose when I was reading about MEGs in Quantitative EEG, Event-Related Potentials and ...
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1answer
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Electric flux and electric field lines [duplicate]

Why we draw finite electric field lines passing through a surface when we can draw infinite ? also why electric flux is proportional to the number of lines passing through a surface ? i am confused ...
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What is the difference between electric field and electric field intensity?

I have read in my text book that electric field is the space or region around a charge in which an electric test charge would experience an electric force, while intensity is the force per unit charge....
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1answer
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Dielectrics and capacitors

Does the electric field after passing through the dielectric reduce. What I mean is If there is a dielectric which is in between the plates ( but NOT IN contact with them ) Suppose field begins from ...
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Electric field of infinite sheet

I have a question regarding the electric field of an infinite sheet in the $x-y$-plane at $z=0$ with a constant sheet charge density $\sigma$. There are many ways to obtain the result $$\boldsymbol E=\...
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Question regarding electric flux distribution in an asymmetrical body

I have a question about how flux will be divided in asymmetric shapes. I encountered this on a test where you have to find the flux through a surface (given below). I placed a symmetric cuboid on the ...
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1answer
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Electric field due to a square sheet, missing by a factor of 2, need insight

So the problem is asking me to find the Electric field a height z above the center of a square sheet of side a I approach the problem a different way than the book, I derive the electric field due to ...
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1answer
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Grounding and equipotential lines

In my textbook it says: One of the rules for static electric fields and conductors is that the electric field must be perpendicular to the surface of any conductor. This implies that a conductor is ...
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2answers
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Does Coulomb's law hold as long as $\dot{\rho} = 0$?

Does Coulomb's law, $$\textbf{E}\left(\textbf{r}\right) = \frac{1}{4\pi\epsilon_0}\int \rho\left(\textbf{r}'\right)\frac{\textbf{r} - \textbf{r}'}{\left|\textbf{r} - \textbf{r}'\right|^3}dV',$$ hold ...
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Field between 2 electrodes experiment

We were asked to conduct an experiment that is as follows: Connect 4.5V constant voltage across 2 electrodes of thin Cu wire, dipped in a tub of copper sulfate solution. A needle is connected to a ...
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Field of a charge inside a spherical shell

Let's for now assume that we have a charge $Q$ at the origin inside of a conducting shell. This means that we have an electric field $$\vec E_1(\vec r)=\begin{cases}\frac{Q}{4\pi\varepsilon_0}\cdot\...
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Electric field produced by oscillating charge

In Feynman Lectures on Physics, Volume 1, Chapter 29 he proves that electric field propagates like a wave. My attempt is like this:- I don't know latex therefore I'm posting the image But to prove ...
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1answer
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If the electric force is the exchange of virtual photons, how can free electrons be accelerated by it?

I know that free electrons can't absorb photons. It is, however, known that electric forces can accelerate electrons. But if electric interactions are merely an exchange of virtual photons, how can ...
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The Electric Potential Energy of a Line of Charge

I want to find the electrical potential energy of a finite line of charge with length "L". I understand how to find the potential but not the potential energy. I´m imagining we would start with an ...
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1answer
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Electric field at source points of any continuous charge distribution

In classical electromagnetism, is there a way to find the electric field at source points of a line, surface or volume charge? If there is a way, please explain in detail My idea: I don't really ...
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1answer
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How is the electric field of light related to its wavelength?

Light is an electromagnetic field. At the same time light is composed of photons; each one carries an energy given by $E=\frac{hc}{\lambda}$. The electromagnetic energy of light is expressed by its ...
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Electric field strength away from a negative spherical charge

I was wonder how would a graph of electrical field strength away from a spherical -ve charge graph would look. Since E= potential gradient I was guessing that since potential increases away from a ...
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1answer
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Is there is any way to prove the Faraday's law of induction?

I want to know if there is any way to prove the Faraday's law or is it just an experimental observed phenomena? More specifically, is there any reason why the proportionality constant is 1? How did ...
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The Kelvin Polarization Force Density Paradox

About 15 years ago as part of a research project, the electrostatic forces on a special cylindrical capacitor were calculated using the standard formulas and officially accepted scientific methods. ...
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Why is $ \nabla \cdot \vec{E} \neq 4 \pi\ k$ times the charge density?

For a line charge with density $\lambda$, we wish to compute the divergence at a point on line charge. We start from definition of divergence: $ \nabla \cdot \vec{E}=\dfrac{d \iint \vec{E} \cdot d\...
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1answer
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Is it possible to have a spherically symmetric constant Electric Field $\vec{E} = E_0 \hat{r}$?

I've been studying the Laplace equation for zero charge distribution: $$\nabla^2 V = 0$$ and I know that this is the general solution to the Laplace equation for an azimuthally symmetric ...
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Why is the electric field phase shifted in this circular plane wave?

The $x$-component of a circular polarized plane wave is $$ E_x(\vec r,t)=E_0\cos\left(\frac{w}{c}(0.6y-0.8z)-wt\right) $$ With only this given, we can devise the total electric field as $$ \vec E(\...
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How is the $E$-field getting canceled between outer and inner surface of a neutral conducting spherical shell?

I am reading Purcell's E&M book and in one of the example questions, it shows that there is no E field between outer and inner surface after a a point charge is located at an arbitrary position ...
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Why Gauss divergence theorem isn't working? [duplicate]

$\vec{E}$ is electric field $r$ is distance between source and field points $\hat{r}$ is a unit vector from source point to field point $x,y,z$ are Cartesian coordinates of field point ...
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1answer
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Will the flux through an arbitrary closed surface be finite or infinite when a plane charge intersects the Gaussian surface?

Let's consider a closed Gaussian surface (in red). The white line and the white shaded part lies inside the Gaussian surface and the black line and the portion above it lies outside the Gaussian ...
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Proof that true passive linear memristors doesn't exist

This is a sequel to the following (now irrelevent) question: My attempt to implement linear memristor Assume the "conceptual symmetry" of the fundamental passive circuit elements holds: Then let's ...
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3answers
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Electric field due to uniformly charged infinite plane sheet

For getting the electric field in this case we use the Gauss's law. we get the equation $$ 2EA = pA/\epsilon_0 $$ here $E$ is electric field, $A$ is the cross sectional area, $p$ is the uniform ...
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Charge inside spherical cavity [duplicate]

Suppose we have a sphere and a cavity inside which is displaced at a distance $d$ from the center. If a charge $q$ is placed in the center of that cavity, a surface charge $-q$ is induced in the ...
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Potential difference in a nonuniform electric field

Let's say I have two points in a nonuniform electric field and those points have the electric potential 10 V and 5 V. If I then would use a voltmeter to determine the voltage between those points ...
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Making sense of bound charge

Given a spherical shell with inner radius $a$ and outer radius $b$ with polarization $\frac{1}{r}\hat{\mathbf{r}}$, the density of the volume charge (inside the shell) is negative the divergence of ...
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Are Kirchhoff's Laws violated in case of varying magnetic field?

I was watching a video of Walter Lewin (8.02x-Lecture 16 to be precise), where he demonstrates an experiment which violates the Kirchhoff's Law. The way I interpret Kirchhoff's laws is by ...
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Should I consider electric field energy density to be negative in plasmonic systems?

Usually electric field energy density is calculated as $\vec E^*\cdot\vec D/2=\varepsilon\cdot\vec E^*\cdot\vec E/2=\varepsilon\cdot|\vec E|^2/2$ and it is positive. But in plasmonic case $\...
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Electric field at any point due to a continuous charge distribution

I am reading Purcell and Morin's Electricity and Magnetism 3rd Edition. Equation ($1.22$): $$\vec{E}(x,y,z)=\dfrac{1}{4 \pi \epsilon_0} \int \dfrac{ρ\ (x^\prime, y^\prime, z^\prime)\ \hat{r}\ dx^\...
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Point charge inside hollow conducting sphere [closed]

Above there is a 2D pic of this problem. $S$ is a conducting sphere with no charge. I am considering the electrostatics case. It is a hollow sphere: inside its cavity lies a point charge $q$,...