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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How fast does an electromagnetic field come into existence? [duplicate]

In this video by the YouTube Channel "Veritasium" it is explained, that electrical energy is in fact not travelling through the wires of a circuit (in the form of electron flow), but instead ...
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2answers
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Can Lorentz force polarize a neutral dielectric atom?

Is it possible to electrically polarize an atom (typically a dielectric) with magnetic field? For example, if dielectric fluid flows near magnetic field, does it shift each atom's positive charge down ...
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Electric field in circuits and potential drop

With reference to the above image: Here the battery produces a constant (will it be constant? pl. explain) electric field across the length of the wire, lets say its value is $\vec E$ . This field ...
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2answers
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Electric field in the center of hemisphere shell without double/triple integrals

I'm trying to derive the electric field in the centre of a solid hemisphere of radius $ R $ where the charge is distributed uniformly. I have seen different methods involving double/triple integrals ...
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13 views

Electromagnetic fields of a spatially bounded time-dependent current which is eventually steady

So here's the set-up: I have a loop in space and fix a point $p$ outside the loop. Then I turn the current on at $t = 0$ (so the current profile is a step-function). Initially at $t=0$ the E&M ...
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2answers
39 views

Electric field inside a wire and potential difference

Suppose I have a battery of $V$ volts and a circuit is made using it. This battery produces a constant electric field which moves the electrons thus establishing current. Now what will happen to the ...
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1answer
58 views

Electric field inside a wire

For a uniform (constant) electric field, we have the relation $E = - \Delta V/\Delta r$. Now, if the electric field provided by a battery is constant over a constant potential difference and if we ...
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1answer
37 views

Is electrical resistance analogous to friction?

In a circuit, an electric field is produced from a circuit element providing a voltage source. Electrons flow through the circuit undergoing collisions which provide a resistive force to the electrons ...
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1answer
26 views

Why does the the electric field intensity is 0 inside a charged conducting spherical shell? [duplicate]

Given a conducting spherical shell with infinitesimal thickness and the radius of $R$. The shell is uniformly charged with surface density $σ$. Find the electric field intensity vector $\bf E$ at the ...
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1answer
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How can two electric plates have a potential difference if the circuit is technically incomplete?

With two electric plates, for example: When the switch is closed, wouldn't the circuit still be incomplete? So I'm not too sure as to why there is still able to be a potential difference. But if the ...
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Creating an electric field

I'm trying really hard to finish making a Van de Graaff generator because I need an electric field to do a demonstration. I'm hoping it generates 500,000 volts. But I found some high volt generators ...
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2answers
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Conversion of potential energy of charge into kinetic energy

Suppose I have a battery of voltage v which can flow $Q$ coulomb of charge through a metalic conductor When voltage is applied across this conductor the electrons inside it get accelerated and move ...
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Electrostatic attraction to electric circuit

Imagine a circuit with a $1$ $kV$ battery hooked up to a $100$ $k$$\Omega $ resistor. Let's also say I had a packing peanut with an overabundance of electrons, so it is negatively charged. Would this ...
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2answers
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Why doesn't the acceleration of an ion in an electric field not depend on the orientation of its velocity in relation to the electric field?

My teacher said in class, " the direction of the acceleration of an ion located in a region without magnetic field but with electric field does not depend on the relative orientation of its ...
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Direction of acceleration of an ion in electric field (but no magnetic field)

Does the direction of acceleration of an ion located in a region without a magnetic field but with an electric field depend on the relative orientation of its velocity with respect to the direction of ...
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4answers
272 views

Alternate explanation for energy flow in electricity as explained in this video

The question is about this video from a youtube channel called Veritasium. It is a popular physics/math youtube channel and topics discussed are usually fact checked and accurate. The gist of the ...
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1answer
344 views

Veritasium Electricity Follow-Ups: Insulators, Switch Location, larger gap

This question is similar to: Doesn't Veritasium's Recent Video About Circuits Violate The Speed Of Light? In what order would light bulbs in series light up when you close a long circuit?, ...
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Why looking from far away the setup looks like as a point charge of magnitude $q1+q2$? Does all field lines (assymptotes) pass through a fixed point? [duplicate]

Doubt came from this figure: like this one field line assume there are many field lines passing through q1 and having asymptotes (dont have proof of why always having asymptotes), does all asymptotes ...
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2answers
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Potential in electric field by magnetic induction

There is a point written in my book (S.L. Arora- Simplified Physics Part-1)- Electric Potential is meaningful only for electric fields produced by stationary charges. It has no meaning for electric ...
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Will an induced electric field reduce the reaction time between two substances?

I've built a Van de Graaff generator that can generate 500,000 volts. When I tried pushing co2 from a tank into a flask of sodium hydroxide solution, it took approximately 3 minutes before the co2 and ...
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65 views

Why looking from far away the setup looks like as a point charge of magnitude q1+q2? Does all field lines (assymptotes) pass through a fixed point? [closed]

Doubt came from this figure: like this one field line assume there are many field lines passing through q1 and having asymptotes (dont have proof of why always having asymptotes), does all asymptotes ...
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1answer
71 views

What formula is this and what does it signify? (Electric Field and Potential)

I probably skipped the useful part of the lecture, but while we were being taught about electric potential energy, my professor mentioned an equation, which he said we will seldom use, but which is ...
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1answer
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Finding $\int_{entire\\space}\overrightarrow{E_B}.\overrightarrow{E_B}dV$ where $E_A,E_B$ are the electric fields of two uniformly charged shells [closed]

Figure shows a uniformly charged spherical shell B of charge $q$ kept inside uniformly charged spherical shell A of charge $q$. Let electric field due to A and B at any point are $E_A$ and $E_B$ ...
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In what way does a charge count as "at rest" or in motion, say within a magnet?

Here: Mechanism by which electric and magnetic fields interrelate User tmac says, The simplest explanation I know of requires only one test charge and two reference frames with a relative velocity ...
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In what sense, physically speaking, are electric and magnetic fields perpendicular? [closed]

I have searched for an answer for in what way are electric and magnetic fields perpendicular, but I only found mathematical explanations speaking of orthogonal vectors and Maxwell's equations and ...
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1answer
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Electric field needed to remove an electron from a Helium atom

Let us consider that we have a Helium atom. We have provided an electric field $E$, which is sufficient to pull out an electron from this atom. We can calculate this electric field as follows : $$eE=\...
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Does the height of a Van de Graaff generator matter?

I'm interested in building a van de Graaff generator as a science project, but when I found some websites that showed how to make one, the height of the housing pipe was tall. If I reduce the height ...
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1answer
58 views

Why electrons accelarate in a solenoid?

The induced voltage in a solenoid equals to the applied voltage $U = L\frac{di}{dt}$. From that I conclude that the electric field generated by the voltage supply and the induced electric field cancel ...
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What is the proof of the expression of force on each individual plate in a parallel plate capacitor with charge Q?

I know the formula is $$F= \frac{1}{2}(QE)$$ where E is the magnitude of electric field between the plates but in our book this is explained by the concept of work done and change in potential energy. ...
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3answers
378 views

Time averages of complex quantities

If an electric field $E$ oscillates as $E_0\sin(ωt)$ then the average value of $E^2$ over one period of oscillation will be $$E_0^2\left< \sin^2(ωt)\right>=E_0^2/2$$ since the average value of $\...
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Electric Field at the center of a cut portion of a sphere

Suppose we have a solid sphere of radius $R$ and of total charge $Q$ uniformly distributed in the volume. We have cut a small portion (a sphere of radius $R/2$) from inside the sphere as shown in the ...
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1answer
53 views

Scalar potential from electric field

I am trying to calculate the scalar potential of a disk located at $z=0$. I determined the electric field along the $z$ axis $$\vec{E}=\frac{\sigma}{2 \epsilon_{0}}\left[1-\frac{z}{\sqrt{z^{2}+R^{2}}}\...
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23 views

Multipoles as a superposition of dipoles?

While navigating on Stack Exchange, I was suddenly wondering about a possibility that I never saw described in my textbooks on electrodynamics. Suppose you have a distribution of electric charges in ...
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Clausius-Mossotti factor for ellipsoides

The dielectrophoresis (DEP) force acting on a sphere involves the calculation of the real part of the complex Clausius-Mossoti factor, which is nothing but a relationship between the dielectric ...
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1answer
58 views

Electric field from a sphere not uniformly charged

I am reading the Feynman courses. It is written inside the book that a sphere of radius $a$ charged by a surface charge $\sigma = \sigma_0cos(\theta)$ should generate an electric field with a moment ...
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Relationship between $\vec E$,$\vec P$,$\vec D$ inside a dielectric material

If we put a dielectric material in region where an electric field $\vec E_0$ is present then, the fields that are present within the dielectric are: $\vec E$,$\vec P$,$\vec D$ . $\vec E$ is the ...
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2answers
23 views

Force on a current-carrying loop due to a uniform electric field

Why does a closed current carrying coil experience no force when placed in a uniform electric field, whereas a charge moving with constant velocity through a uniform electric field does?
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2answers
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When an electrical field is generated inside a Faraday cage (say as in a microwave) does the cage act as a reflective surface to amplify the field?

I am familiar with the concept that electrical fields within a Faraday cage do not extend outside of the cage and that electrical fields generated outside do not extend into it. My question is -- when ...
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1answer
37 views

Is field strength a scalar or a vector?

I'd imagine strength to be a scalar quantity. My intuition says that how strongly a force is experienced, ie its magnitude, has nothing to do with the direction it is experienced in. From what I ...
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1answer
30 views

Confusion concerning notion and origin of electrostatic potential

An elementary circulation is mathematically defined by: $dC$=$\overrightarrow{OM}$.$\overrightarrow{X}$. Now, we aplly this to a ponctual charge: $dC$=$\overrightarrow{OM}$.$\overrightarrow{E}$ And we ...
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2answers
62 views

Why is the electric field caused by a infinite plate the same no matter the distance from the plate?

I understand why the field is perpendicular to the plate at all distances $R$ from the plate but can't understand why the strength remains the same. If we calculate $E$ using Gauss Law I understand we ...
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1answer
32 views

How do I find the electric field at the middle point in a thin long strip whose cross section is a semicircle?

A thin long strip whose cross-section is a semicircle carries a uniform surface charge of density s on its inner surface. Find the electric field at a point O located midway on its axis. Link of ...
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4answers
76 views

Why is voltage used when measuring the strength of a battery and not electric field?

I'm not sure how to ask this but, I started learning about electromagnetism with how charged particles behave in electric fields. This was easy and intuitive to understand. But I felt a disconnect ...
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3answers
93 views

Why is the concept of potential used so loosely?

What does potential of a conductor actually mean? As I have understood it potential is the amount of work done by an external agent to bring a unit positive charge to a point of consideration. It is ...
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1answer
55 views

Fourier Transform of the vector $\vec{E}(\vec{x}, t)$ and its direction

In chapter $\textit{13.3 - Density Effect in Collisional Energy Loss}$ of $\textit{Classical Eletrodynamics}$ by Jackson, it says that: The problem of finding the electric field in the medium due to ...
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3answers
57 views

Gauss law apparent violation

If we assume to place a dipole or a quadrupole inside a Gaussian surface, then the Gauss law will give zero electric field outside Gaussian surface at any point since enclosed change is zero. However,...
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2answers
40 views

Increasing capacitance of a capacitor [duplicate]

In my book, it's given that: ”Principle of Capacitor: In the capacitor arrangement, the increase in capacitance of a conductor is due to the decrease in potential V (charge Q remains constant) when ...
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1answer
41 views

Dielectric material between two plates

I wonder if the capacitance is the same if we have two plates with a dielectric material between. I mean, is it the same when the dielectric material only touches one of the plates, compared with when ...
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1answer
42 views

Which of these videos is more accurate about how perpendicular polarized filters block out light?

This wiki describes why perpendicular fields block out light: https://en.wikipedia.org/wiki/Polarizer#Wire-grid_polarizers "Electromagnetic waves that have a component of their electric fields ...
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Calculating the surface charge density as a function of $X,Y$

$x$-$y$ plane is a conducting plate stretching to infinity. A charged line is placed from $(0,0,0)$ to $(0,0,L)$. It has charge density function of ${\lambda=\lambda_L\frac{z^2}{L^2}}$. Calculate the ...

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