The electric-field tag has no wiki summary.
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How can a non-conservative field be a scalar multiple of a conservative field?
Okay so I was reading this from University Physics by Freeman and Young and on the topic of inductors as circuit element, they wrote that $\mathbf{E_c} + \mathbf{E_n} = 0$ which makes no sense to me
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2answers
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Using Gauss's Law to calculate electric fields between plates
I have two earthed metal plates, separated by a distance $d$ with a plane of charge density $\sigma$ placed a distance $a$ from the lower plate. I want to derive expressions for the strength of the ...
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1answer
169 views
What is discontinuity in Vector Fields
I am reading David J. Griffiths and have a problem understanding the concept of discontinuity for E-field.
The E-field has apparently to components. (How does he decompose the vector field into the ...
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2answers
175 views
In which cases is it better to use Gauss' law?
I could, for example calculate the electric field near a charged rod of infinite length using the classic definition of the electric field, and integrating the: $$
\overrightarrow{dE} = \frac{dq}{4 ...
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2answers
569 views
Electric potential of sphere
(a) I am a little confused about this part. The point at A to B isn't radial. The electric field is radially outward, but if I look at the integral
$$\int_{a}^{b}\mathbf{E}\cdot d\mathbf{s} = ...
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why is total electron energy of an electron in metal negative?
In my textbook, it says that any electron bound in metals, modelled as some potential well $U$, has negative total electron energy, as shown below in the figure.
Why is the total electron energy ...
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1answer
95 views
Why does a point charge generate an electric field and why is an electric field represented by this formula?
Why does a point charge generate an electric field and why is an electric field represented by this formula
$$E ~=~ \frac{q}{4 \pi \epsilon r^2},$$
where $\epsilon$ is permittivity of free space ...
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4answers
313 views
Why does it seem that the potential difference dependence of capacitance and total energy stored in a parallel-plate capacitor are contradictory?
Consider a parallel-plate capacitor. Charge is stored physically on electrodes ("plates") which are flat and parallel to one another. If one electrode has charge $+Q$ and the other electrode has ...
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Why do you get electric field of a light wave?
Why do you get electric field of a light wave in following form: $E(x,t)=A cos(kx-\omega t- \theta)$?( look at: https://public.me.com/ricktrebino -> OpticsI-02-Waves-Fields.ppt, p. 18)
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3answers
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How does electricity flow in conductor when potential difference is applied?
Electrons move from higher potential to lower potential. When a conductor is connected to battery, electron move from negative terminal to positive terminal.
But the battery itself forms a Electric ...
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4answers
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In electrostatics, why the conductor is an equipotential surface?
Since the electric field inside a conductor is zero that means the potential is constant inside a conductor, which means the "inside" of a conductor is an equipotential region.
Why books conclude ...
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How can find the electric field at the center of a semicircle (insulation material)? [closed]
I have a thin wand of insulating material. The wand is bent so as to form a semicircle of radius $R=20 cm$. The wand is a uniformly distributed charge $q= 5\ 10^{-9} C$. Calculate the electric field ...
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1answer
548 views
Can lightning be used to solve NP-complete problems?
I'm a MS/BS computer science guy who is wondering about why lightning can't (or can?) be used to solve NP complete problems efficiently, but I don't understand the physics behind lightning, so I'm ...
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1answer
272 views
Improvement Of Soft Iron And Steel As Magnets
I am given to know that soft iron is used as temporary electromagnet since it has high permeability i.e. the ability to align its domains corresponding to the electric field around it, however has a ...
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2answers
390 views
Is the electric field zero inside an ideal conductor carrying a current?
By an ideal conductor, I mean one with zero resistance. Inside an ideal conductor with no current, the electric field is zero, but is the electric field still zero with the ideal conductor carrying a ...
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1answer
957 views
Force from point charge on perfect dipole
Have a point charge and a perfect dipole $\vec{p}$ a distance $r$ away. Angle between $\vec{p}$ and $\hat{r}$ is $\theta$. Want to find force on dipole.
I'm having more than a little difficulty ...
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1answer
196 views
Existence Of Electric Field Lines
Can an Electric Field with field lines Like So Exist:
One Of my friends said it couldn't as the field lines here are not conservative ; so it cannot exist ; Is he right?
Or can it be made to ...
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1answer
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Equipotential Contour mapping and making it 3D [closed]
I have seen Contour diagrams for Equipotentials . That are drawn like so:
I also saw One image for these contours that was in 3D (Negative Point Charge) :
I was Wondering If there's any ...
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2answers
414 views
Electricity & Magnetism - Is an electric field infinite?
The inverse square law for an electric field is:
$$
E = \frac{Q}{4\pi\varepsilon_{0}r^2}
$$
Here: $$\frac{Q}{\varepsilon_{0}}$$
is the source strength of the charge. It is the point charge divided ...
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1answer
88 views
$\mu$T in to $\frac{W}{m^2}$ (for interpreting EMF readings)
I am considering purchasing an EMF reader, to collect data about what is being thrown off of power lines and various other sources in the house to reach some conclusions.
An issue is, the meter can ...
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2answers
491 views
A closed surface, no charge enclosed, yet flux not 0?
!
The book says it is $E_0\pi r^2$ because the flux through the circle is equal to the curved part of the paraboloid.
I don't understand this, shouldn't the total flux be 0 for the whole surface? ...
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Calculating the number of turns and thickness of an electromagnet
I want to calculate the number of turns of an electromagnet and the thickness of the wire.
But i have tried to search arround in books, and can't really find any thing.
I know my wire is 0,114mm and ...
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1answer
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Why we cannot use Gauss's Law to find the Electric Field of a finite-length charged wire?
One of my physics books has a nice example on how to use Gauss's Law to find the electric field of a long (infinite) charged wire. However, at the very end of the example, the author ends by saying ...
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2answers
307 views
Electric fields in/around conductors
So according to my notes, the field inside a conductor is zero. But what, exactly, is meant by inside?
I think we are in electrostatics for the purpose of this question.
The reason it is zero is ...
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2answers
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Derivation of Electric Force between Parallel Plates
So the electric field between two parallel plates is given by $E = V/d.$ How do you derive this?
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Rotating Disc and Magnetic Field [closed]
I'm studying for exams, and I am curious as to how the rotation of a disc would affect the magnetic field. The following problem stumps me:
A plastic disc of radius $R$ has a charge $q$ uniformly ...
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1answer
285 views
Electric Flux Density - Ring Charge
A ring placed along $y^{2}$ + $z^{2}$ = 4, x = 0 carries a uniform charge of 5 $\mu$C/m. Find D at P(3,0,0)
Should I be using Gauss's Law to solve this problem? I was considering using a spherical ...
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0answers
113 views
What is the electric field part of an EM wave? Radiation field or the induction field?
Look at this image:
I wonder if the electric field is from the induction field from a vibrating electron or the radiation field? If it is from the radiation field, as I suppose, than can someone ...
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1answer
475 views
Where will the electric field be zero in dipole [closed]
Lets say we have an electric dipole. I can't figure out where the location of net zero electric field will be.
Tnx
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2answers
470 views
Boundary conditions for static electric field
Consider a surface that carries surface charge density. In electrostatics, boundary conditions are studied by showing that there is a discontinuity in the normal component of the electric field across ...
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1answer
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Scaling of Static Electric Field
The electric field of a point charge goes like $\displaystyle\frac{1}{r^2}$
The electric field of an infinite line goes like $\displaystyle\frac{1}{s}$
The electric field of an infinite plane is ...
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2answers
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Gauss' law giving zero field where field is not zero?
Two plastic sheets with charged densities as shown:
I'm trying to find the field at $B$. I obtained the correct answer by adding up the fields created by each charge density. But I realized that ...
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2answers
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Fields versus Photons
Does the field of a set of photons behave differently from a single photon.
e.g. Suppose I have a group of photons with their Electric fields $\mathbb{E}_n$ all aligned. So
$$\mathbb{E}_{\text{tot}} ...
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2answers
91 views
Origin of field deduced from potential
Related: Tubelights+power lines pictures?
I would've edited this into the above question, but I realized that there' enough to it to qualify as a new one. Plus this seems to be a confusion of ...
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1answer
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Tubelights+power lines pictures?
I've come across many pictures like these, sometimes in chain emails reporting the dangers of power lines.
Another claim is that they run on "wasted" energy.
The explanations given are that the ...
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Current in a simple circuit
I was going over my notes for an introductory course to electricity and magnetism and was intrigued by something I don't have an answer to. I remember my professor mentioning, to the best I can ...
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2answers
385 views
Help me find electric field strength vector for this given equipotential line
I'm a physics tutor. This is the question from a High school book.
The equation of an equipotential line in an electric field is y = 2x,
then the electric field strength vector at (1, 2) may be ...
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1answer
348 views
Given charge distribution find electric field
Given a charge distribution $\rho(\vec{r})$ where $\vec{r}$ is the position vector and that $\rho$ is a function of only $|x|$, Why is it that the corresponding electric field $E$ is necessarily of ...
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Electric field at a point inside a capacitor
Let's say I have a parallel plate capacitor.
How would I find the electric field at a certain point INSIDE the capacitor (inside the dielectric let's say). From what I understand, the flux of the ...
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3answers
204 views
Gauss' law - changes in the magnitude of E field inside the closed surface
Gauss's law says that the flux through a closed surface which contains neither a sink nor a source will be zero.
It's quite clear that all field lines will have to exit somehow, but the
strength of ...
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1answer
148 views
Complex Potentials, Potentials and Fields
Suppose an electric field $E=-\nabla \psi$ where $\psi=-Q\ln r$ where $Q$ is just some constant and I have found its harmonic conjugate to be $-Q\theta+c$ where $c$ is some constant. What does it say ...
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2answers
668 views
How to calculate the electric field at a point in space
Let's say I have a uniformly-charged wire bent into a semi-circle around the origin. How can I find the electric field (magnitude and direction)
I'm not even sure if I should use Coulomb's or Gauss' ...
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1answer
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Electric field due to nonconducting plastic sheets [closed]
Two very large, nonconducting plastic sheets, each 10.0 cm thick, carry uniform charge densities $\sigma_1, \sigma_2, \sigma_3$ and $\sigma_4$ on their surfaces (the four surfaces are in the ...
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0answers
268 views
How to find the electric field at a point based on a uniformly charged surface
What is the general solution to finding the electric field at a point based on some (or multiple) charged surfaces. I know that we can perform a line/surface integral if a charge is close to a wire or ...
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Is it true that $\vec{E}\neq 0$ inside a 1- or 2-dimensional conductor?
It is known that when a conductor is placed in an electric field, the charges redistribute themselves such that $E=0$ inside the conductor. I was also told that the same is NOT true for the 2D and 1D ...
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487 views
Is there really no meaning in potential energy and potential?
I have been told all my physics life that potential energy between two mass/charge has no meaning and only their difference has meaning. The same goes for electric potential, only the difference ...
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617 views
Electric field problem
First of all I hope I'm doing the right thing by posting this message on the stack exchange site. I know you aren't my personal problem solvers, but I just can't solve it. And maybe this problem is ...
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1answer
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Law of conservation of energy at the space.? [closed]
Energy can neither be created nor be destroyed,
if energy disappear in one form it will reappear in another form without any loss.
so what will happen if FAN switched on in the space. ?
1.Electrical ...
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5answers
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What is the origin of the Dirac delta term in the dipole electric field?
I am a bit lost how one has deduced the formula for electric field with electric dipole because of some inconsistency between different sources. The Wikipedia article contains a delta function in the ...
