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 of fields.

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16 views

Determining the z-component of the electric field at a point near a plate [on hold]

I'm struggling with all three parts a,b,c. Any help would be great, thanks. Regards Roy Browning
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43 views

Does the electric field of a charged particle really contribute to its mass? [duplicate]

An electron at rest creates a static distribution of an electric field around it. Wherever the particle moves, it carries or drags the field with itself. Does this electric field contribute to the ...
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18 views

How does change in magnitude of a point charge reflect change in its electric field at a particular point in space with respect to time?

We know that electric charge of an object results in an electric field formed around it. We also know that varying the magnitude of a point charge does not instantly produce a change in the electric ...
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19 views

Electric Field in conductor near Solenoid

My question is essentially a follow up to this question. It's answer says, the mobile charges in the conductor distribute themselves to make E = 0 inside the conductor. But, I don't understand how a ...
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1answer
31 views

$E$-field of a uniform distribution of charge at 3D point [on hold]

How can I find Electric field of a uniform distribution of charge at 3D point?
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44 views

Gauss law use not in free space

Gauss' law specifies permitivity for free space. what happens if electric field is not in free space. does the law apply?
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34 views

Tangential component of electrostatic field on a charged surface?

This is a question from class 12 Physics NCERT Part I: Show that the tangential component of electrostatic field is continuous from one side of a charged surface to another. [Hint: Use the fact ...
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2answers
32 views

Components of Electrostatic energy to components of electric field?

I'm trying to understand the relationship between electrostatic energy and the electric field so that I can compute electric field components from electrostatic energy components. Is it correct to ...
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10 views

Energy stored in a sphere of variable charge density

I have seen a derivation of the energy stored in a uniformly charged sphere. However, I would like to generalize this derivation to include a variable charge density (varying with radius). The ...
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1answer
45 views

Why is the electric field of a conducting sheet of charge double the electric field of just a sheet of charge?

I was reading Feynman's Lecture on the Application of Gauss' Law and I came across this: Source This really confused me. What are the "other" charges he talks about? How does the additional field ...
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18 views

Force of attraction in capacitor [duplicate]

In a question, it was asked the force of attraction between the plates of a parallel plate capacitor. and it was solved as $$\frac{(1)(C)(V^2)}{2}=(F)(d)$$ $$F=\frac{(1)(C)(V^2)}{(2)(d)}$$ and I ...
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1answer
30 views

Significance of the negative sign in $V=-\int \vec E · \mathrm d\vec r$ [duplicate]

Why is there a negative sign in the relation $$V=-\int \vec E · \mathrm d\vec r$$ between the electric field and the electric potential? Is this because of some derivation in vector calculus because ...
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1answer
56 views

Why can't we have an $E$-field like this one inside a conductor?

From what I understand, there can be no $E$-field inside a conductor in an electrostatic situation, because had there been any field within it, the charges on the surface would start to move, thus ...
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1answer
32 views

How does induction work when a body is charged (ie) not neutral?

I know that for a neutral body, if a point charge is placed next to it, induction works something like this: Consider a uniformly charged conducting body with charge Q on it. We place a positive ...
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1answer
12 views

On direction of electric field in a battery

I know that the electric field points from positive to negative potential in a circuit but it is opposite inside a battery for the purpose of continuity of electron flow and electric field....but why ...
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1answer
35 views

Electron in crossed fields [closed]

A homogenous magnetic field $ \overrightarrow{\boldsymbol{B}} $ is perpendicular to the electric field $ \overrightarrow{\boldsymbol{E}} $ in a plate capacitor with the plates $d$ distance apart. From ...
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1answer
39 views

Doubt in the derivation of Gauss's law in dielectrics

so in the 2nd page,when the dielectric material is introduced the gauss's law becomes $$\oint _ { S } \vec { E } \cdot \vec { d S } = \frac { ( q - q _ { i } ) } { \epsilon _ { 0 } }$$.But my ...
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2answers
47 views

Regarding the $E$-field at the location of discrete point

Most textbooks define the $E$-field at the location of $q_{1}$$\\$ as: $$\textbf{E}=-\frac{q_{2}}{r_{21}^2}\hat{\textbf{r}}$$ which is finite. However, the field is also defined as the force per ...
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22 views

How to calculate the velocity and radius of curvature of a charged particle in a perpendicular magnetic and parallel electric field?

If I have a charged particle come from a point velocity V1 where there is a uniform electric field parallel to the motion of the particle which accelerates it and a magnetic field perpendicular to ...
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1answer
51 views

Coulomb's law and the continuous charge model in an infinite charged plane [duplicate]

The $E$-field of an infinite plane with a uniform charge density $\sigma$ has a constant magnitude equaling $2\pi\sigma$. Now, this magnitude assumes a continuous charge model throughout the plane. ...
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1answer
42 views

Is there an easy way to tell whether this “Curlmeter” would rotate or not?

Let us say we have the following symmetrical apparatus: Four equal positive charges, all connected to a shaft that can rotate, the connecting rods are insulated, and so does the shaft. Now ...
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2answers
57 views

Null electric field at infinity? How? [closed]

Suppose there are two charges (4uC each) fixed in the horizontal axis. One is in x=0 and the other in x=8m. I've obtained the electric field: $E=-k\cdot4\mu C \cdot [\frac{1}{x^2}+\frac{1}{(x-8m)^2}]...
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2answers
122 views

Derivation of Ampere's Law from Biot-Savart

Our aim is to derive $\nabla\times \mathbf B=\mu_0(\mathbf J+\epsilon_0\frac{\partial E}{\partial t})$. To begin with, let $ \mathbf A=\frac{\mu_0}{4\pi}\int_{\mathbb R^3}\frac{\mathbf J(\mathbf r')}{...
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38 views

How electric field and magnetic field propagate through vacuum where there's no charge present? [duplicate]

As we know light travels as an electromagnetic wave...but electric fields and magnetic fields are interactions between charges...they are the forces acting on stationary and moving charges ...
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1answer
20 views

Electrical energy of a charge distribution and the work required to assemble it

The electrical energy of a charge distribution is equal to the integral of $\,E^{2}dv/8\pi$ over all space, and if I have a charge distribution of finite extent, then the energy is finite. Moreover, $...
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1answer
25 views

Path independence of the line integral of the electrostatic field created by an arbitrary charge distribution

Suppose we have the following situation: A positive arbitrarily shaped charge distribution. The line integral of the total electric field, generated by the whole distribution, from $A$ to $B$ is ...
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1answer
39 views

Candle in external electric field [duplicate]

We put candle in electric field. My question is: Ions of flame move or ions of air? It is written that flame heat air molecules and convert them to ions, then positive ions of air heavier than ...
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42 views

How does the electric field inside a conductor become zero? [duplicate]

When a conductor is placed in an external electric field, I know that the free electrons arrange themselves in such a way that the field inside the conductor due to these charges cancel the external ...
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1answer
18 views

Why can't I see any bubble in my anode during my electrolysis experiment

I am doing an electrolysis experiment using this apparatus The left side is the anode and the right side is the cathode. I am using two 9v battery in series (total 18V DC) to power my apparatus. ...
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58 views

Candle in electric field [duplicate]

In above picture, we put a candle in electric field. which is picture correct?why?
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1answer
31 views

Understanding DC motor torque [closed]

I am building an rc car from zero and i got stuck into a little problem.My dc motor torque is 20g/cm and using gears I have achieved a ratio of 125:1 so that means i now have 20*125 = 250g/cm. My ...
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89 views

Condemnable limit for the electrostatic field? [on hold]

When we define the electrostatic field (law's Coulomb), generated by a $Q$ charge calculated in a point $P$ of the space, we place a particle with a small positive charge $q_0$, called a test charge ...
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4answers
69 views

Electric field of point charge

in above picture, we have two point charge ( same size ). Does electric field of q2 at location of q1 depend on size of q1? because we know when we want to measure electric field of a charge, use ...
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3answers
38 views

'Electrostatic field of a circuit' What does it mean?

I've recently gotten into electrodynamics, I've studied electrostatics & magnetostatics, so far I know these facts: Electrostatic fields are produced by static charge configurations Magnetic ...
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1answer
29 views

Electric field due to changing uniform magnetic field

I think this could be a misunderstanding on my part , still I want to clarify this.Suppose in a region of boundless expanse, there is a uniform magnetic field which changes at a rate $\frac{d\phi}{dt}$...
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2answers
37 views

Why is electric flux through a closed surface with charge inside non zero?

"If a closed surface does not have any charge inside where an electric field line can terminate, then any electric field line entering the surface at one point must necessarily exit at some other ...
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1answer
60 views

Electric field of Charge

in above picture,we have a fixed positive charge. this positive charge create electric field in its surrounding. we consider a special point in left of positive charge. Is electric field different ...
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15 views

Can electric fields pass through grounded surfaces?

Let's assume there is a grounded surface with which is infinite in length and width. If my understanding is correct, the grounded surface should have zero electric potential. So, if we assume an ...
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2answers
43 views

Signs in application of Gauss's law to a sheet of charge

In Purcell's Electricity and Magnetism, page 52, the author said that in the following situation: [Where we have a slab of positive charge with uniform density $\rho$. $\,\bf{E_{1}}\,$ is the $E$-...
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50 views

Electric Field Intensity

The electric field intensity everywhere is $E=E_0-j$ (y-direction) in vacuum (say $E_0=5$). if you have an infinite-perfect conductor starting at the $x \geq 4$ plane and $x < 4$ is vacuum. What ...
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1answer
9 views

Charge on an electrical conductor

Consider we have very precise equipment (s) needed for this question. There's a finitely big uncharged conducting sphere. Suppose we had an extra electron from an external source and we plan to keep ...
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1answer
51 views

In electrostatics, why can't we tell how much energy is located in a volume inside the $E$-field?

In Purcell's Electricity and Magnetism, page 32, it is stated that the potential energy $~U$ of a system of charges is given by (using cgs units): $$U=\frac{1}{8\pi}\int_{\mathrm{Entire \\field}} E^{...
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1answer
39 views

Strange electromagnetic phenomena

Well, I have some doubts about two electromagnetic phenomena that may be related so I wanted to ask you if you could explain them to me. The first one happend some days ago: I was about to go to bed,...
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1answer
38 views

Why isn't the water moving when it is undergoing electrolysis

I understand that in electrolysis of water, the water around cathod is splited in the way of 4H2O + 4e => 2 Hydrogen + 4 OH- . And the hydroxide will move to the anode due to electric field in the ...
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4answers
46 views

Electric field line density : Theory vs Reality

I've already went through this post. Yet, I still can't understand the meaning of "density" of electric field lines whose number is, in reality, infinite. One of the answers , for instance, states ...
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1answer
22 views

Cylindrical capacitor, why is the electric field radial between the two plates?

I'm trying to understand why if I consider a cylindrical capacitor whose height is $h$, the radii are $R_1$ (external) and $R_1$ (internal) and I put myself between the two plates I can say that the ...
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2answers
77 views

Electric field of a point source in QM

We know that radiation from a point source vanishes at large distances. So when an atom emits a photon, the expectation value of the electric field must vanish at large distances. How we can explain ...
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1answer
43 views

Electric field of infinitely extended flat plate [closed]

I am reading an example how to calculate the electric field of infinitely extended flat plate and I have trouble to understand certain steps $$ E_{z}=\frac{1}{4 \pi \epsilon_{0}} \int_{0}^{\infty} \...
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1answer
93 views

Gauss' law for two point charges and a factor of $4\pi$

When we model electric field as something that represents the "flow" of something that is conserved, we can prove that the flux due to a single point charge, through the following surface, Flux ...
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3answers
82 views

Electric Field vs Distance (Contradiction)

There was a text book question in my physics class this morning on what happens to the strength of an electric field $E$, if its distance between two plates decreases by 2 fold. My initial thought ...