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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Complex electric field in second order polarization

I am reading an introductory article on nonlinear optics. Here is what the part that's troubling me says: $$\tilde E(t) = Ee^{-i\omega t} + \text{c.c} $$ When this electric field is incident on a ...
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1answer
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Does constructive interference automatically imply bright fringes at all times?

Suppose two waves interfere constructively at some point, in a double slit experiment set-up. This essentially means that the two waves have their peaks and troughs in sync with each other, and there ...
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1answer
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Interaction between electron and electric field

Let consider that we are using parallel plates to create electric field. And let assume that there are small holes in both the plates (holes on both the plates are aligned). Now if we bring a electron ...
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1answer
23 views

How does the electric field pattern looks like when current is moving inside the conductor and why this field is uniform?

We know that electric field is uniform inside a normal electric circuit consisting of some battery source and a conducting wire , $\mathrm{E}$ will be $\mathrm{E=V/d}$ , but I cannot think of a reason ...
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Charged particles simulation in different planes

I have been trying to figure out an analytical/numerical method to calculate the following: there is a charge distribution (gaussian) of positive charges in a plane, whereas there are negative charges ...
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2answers
73 views

What is the electric field in a region of constant potential?

I am working on a problem set on electrostatic potential and there is this one particular question posed that states "The electric field in a region of constant potential is?". The answer ...
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1answer
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44 views

Electric field of a configuration of five parallel infinite slabs of dieletric materials

I am having a hard time trying to figure out how to proceed in order to calculate the electric field of a configuration of five slabs of dieletric (insulating) material (actually one of those is ...
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2answers
88 views

Why does near-field attenuate at $\frac{1}{r^6}$?

So far-field makes intuitive sense to me, it attenuates at $\frac{1}{r^2}$ much like gravity. This is just common sense since the area for the surface of a sphere relative to its radius has a $r^2$ ...
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1answer
82 views

Connection between quaternions and electromagnetism

Consider the multiplication of two quaternions, which can be written as a matrix equation: $$ xy = \begin{pmatrix} x_0 & -x_1 & -x_2 & -x_3 \\ x_1 & x_0 & -x_3 & x_2 \\ ...
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3answers
45 views

What is the definition of direction of current?

Wikipedia defines the direction of current as: The direction of conventional current is arbitrarily defined as the direction in which positive charges flow. But suppose a region where there is a non-...
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1answer
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Does electrically neutral mean the potential is zero?

I don't know if this is a silly question, but I have a homework problem that tells me a line charge is electrically neutral at time $t=0$. I was calculating the potential from the definition $$ V(\...
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2answers
74 views

What is the precise definition of *direction* of current and of current element for a conductor?

The Biot–Savart law states that magnetic field due to an elemental cylindrical system through which a constant current $I$ is passing at a point $r$ distance away is given by $$d\vec{B}=\frac{\mu_o}{4\...
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2answers
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Why is the magnetic field around a straight current-carrying wire in concentric cirlces?

I have a question that, why are the magnetic field lines around a straight current carrying wire in the form of concentric circles? If the wire is carrying current, it is acting like a magnet. So ...
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4answers
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Total Energy of an electromagnetic wave

This question may sound stupid. But why when we calculate the total energy density (energy/volume), carried by an electromagnetic wave $u_T$, we add both $u_B$ + $u_E$. Where $u_B = \frac{B^2}{2\mu_0}...
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2answers
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$\delta(t) = E(t) e^{-i[\nu t + \phi(t)]}$: the "positive frequency part of the electric field"

I have the time dependence of the electric field $A(t)$ written in terms of the amplitude $E(t)$ and phase $\phi(t)$ as $$A(t) = E(t) \cos[\nu t + \phi(t)].$$ I am told that this varies slowly in an ...
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$A(t) = E(t) \cos[\nu t + \phi(t)]$ varies slowly in an "optical period" of $2\pi/\nu$?

I have the time dependence of the electric field $A(t)$ written in terms of the amplitude $E(t)$ and phase $\phi(t)$ as $$A(t) = E(t) \cos[\nu t + \phi(t)].$$ I am told that this "varies slowly ...
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2answers
51 views

How can there be zero electric field in the marked region (in the image) in the conductor?

as the marked region is nearer to surface with positive charge density should there be a net electric field instead of 0?
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1answer
28 views

How would one calculate the electric field produced by a piezoelectric device in response to a sound wave?

So the governing equations of piezoelectricity are: Where E is the electric field, D is the displacement field, S is the strain, and T is the stress. Say I have a piezoelectric device where the ...
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5answers
94 views

The electric field formula $E=F/q$

If we follow the formula $E=F/q$ it says that when the force is bigger the electric field is bigger as well but if the charge on which the force is being exerted to bigger the electric field is ...
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1answer
36 views

Finding the sum of electrical field vectors [closed]

Suppose at point P the electric field $\bf{E_1}$ is 450 N/C in the positive y-direction and the electric field $\bf{E_2}$ is 600 N/C 36.9 degrees from the negative y axis toward the x-axis. Find $\bf ...
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1answer
40 views

Direction of electric field while taking infinity

A positive charge $q$ is placed somewhere. So electric lines of forces will be radially outward from this charge. While defining potential at a distance $r$ from $q$, we say it is the work done to ...
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1answer
80 views

I am not able to convince myself with the gauss law, explain why the situation below shouldn't have non-zero flux?

I have drawn an image of a spherical surface and positive charge outside it. As the positive charge is outside the sphere the electric field incident at every small surface is different from the other ...
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1answer
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Can we give a desired direction to the electric field by connecting the wires to one terminal having some potential?

Let's say we have a battery and one wire is connected to the one terminal having let's say some positive potential and other end of the wire is connected to the plate which is from one side it is ...
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0answers
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Electric field in a supercapacitor/electrophoretic system

I'm trying to understand how the application of electric potential acts in between two electrodes in a capacitor-like structure (parallel plates or cylindrical electrodes) immersed in a solution with ...
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0answers
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Equation of path traced by a charged particle in time varying magnetic field

Is there anyway to figure out the equation for trajectory of a charged particle in a magnetic field(which varies with time) increasing inside the plane of the screen, the particle is outside the ...
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0answers
63 views

Why would this integral of the time derivative of the electric field equal zero?

I'm reading electrodynamics physics notes that describe a 1-dimensional cavity of length $L$. The cavity is said to lie along the $z$-axis from $-L$ to $0$. There is a reflective mirror at $z = 0$, ...
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0answers
201 views

Why would this integral of the time derivative of the magnetic field equal zero?

I'm reading electrodynamics physics notes that describe a 1-dimensional cavity of length $L$. The cavity is said to lie along the $z$-axis from $-L$ to $0$. There is a reflective mirror at $z = 0$, ...
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2answers
39 views

Why charge induce inside doesnt depend on what the outer potential is, in a conductor?

Let's suppose we have a conducting shell which has an outer radius $R$ and inner radius $r$. A charge is kept inside (not at the centre). We know that a charge will be induced in both surfaces. But ...
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1answer
26 views

Why is the Electric Field from Point Charges vs a Continuous Line Different?

I was doing some calculations regarding the difference between the electric field generated by point charges vs a continuous line of charge (trying to come up with a cool/challenging physics problem), ...
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1answer
21 views

Electric field inside a non-uniformly charged conductor

With Gauss's Law, if we take a uniformly charged hollow sphere for instance, the electric field inside the hollow sphere is 0 because there is no charge inside. However, what if this sphere is not ...
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1answer
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Relativity and Electromagnetism: why doesn't every current-carrying wire generate a perpendicular electric field?

I was looking at Purcell's derivation of a current-carrying wire's magnetic field using the Lorentz transform, and noticed something which bothered me. It assumes that the distance between positive (...
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1answer
55 views

Does the number of electrons colliding in wire get double as the length of wire gets doubled?

Does the number of electrons colliding in a wire get doubled when length of wire is made twice with its area of cross-section remain constant. My calculations for this are:- For wire of length $L$: ...
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2answers
42 views

Electric field of moving charge

Does the electric field of a moving charge (constant velocity) change with time? Or it remains the same? I know that changing electric fields produce a magnetic field, but in a straight, current-...
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0answers
58 views

Electrical conductivity/resistance of gas or vapor in an electrostatic field at normal temperature and pressure

For liquids (e.g. liquid metal and water), I could find their electrical conductivities (unit in S m$^{-1}$) or resistances in the CRC handbook. Also, I noted that equations for calculating the ...
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2answers
47 views

Electric field in a vacuum

By changing the magnetic field can we generate electric field in a vacuum ? By the Faradays law of EMI if the magnetic field associated with a coil changes, current is induced in that coil So if we ...
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1answer
47 views

On the dielectric constants of liquid and vapor phases of a material

I can find the static dielectric constant of materials on the website or in a handbook. But for some liquids, it only shows the dielectric constant at the saturation vapor pressure. I am confused that ...
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2answers
45 views

Question about the sign of $\mathbf{E}\cdot d\mathbf{l}$ when computing the Electric Potential [duplicate]

I have a question on the derivation of the electric potential for a single charge located at the origin. The electric potential is defined as $$V\left(\mathbf{r}\right)=-\int_{\mathcal{O}}^{\mathbf{r}}...
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1answer
30 views

Derivation of the electric potential inside a non-conducting sphere

Assuming that the electric field at a distance $r$ from the center of a non-conducting sphere with radius $R$ and uniformly distributed charge $Q$ is $E=\frac{1}{4\pi\epsilon_0}\frac{Q}{R^3}r$, we are ...
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3answers
68 views

Question about electromagnetic radiation

I was taught that , in a electromagnetic radiation , changing electric field is produced due to oscillation of charge this changing electric field give rise to 'changing' magnetic field and this ...
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2answers
50 views

Producing constant constant electric field [closed]

Can we create constant electric field using varying magnetic field? And also , How the varying magnetic field give rise to varying electric field not a constant electric field .
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1answer
170 views

Expansion of the derivatives of the electric and magnetic fields

I'm reading electrodynamics physics notes that describe a cavity of length $L$. The cavity is said to lie along the $z$-axis from $-L$ to $0$. The electric field is polarized in the $x$ direction and ...
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2answers
34 views

Electric field inside current carrying conductor

Is the electric field inside current carrying conductor changing electric field or it is a constant electric field? And how this electric field produce magnetic field?
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46 views

Changing magnetic and electric field

Does a changing electric field create 'constant' magnetic field or 'changing' magnetic And , does a changing magnetic field create 'constant' electric field or 'changing' electric field
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2answers
44 views

Why reversing the direction of electric current reverses the magnetic fields' direction?

I don't understand why magnetic field gets reversed when the electric current is reversed. So I searched on the internet but couldn't find any answer. Could someone plz explain this phenomenon?(with ...
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2answers
80 views

According to Gauss's theorem the integral of $\vec \nabla⋅(\phi \vec E)$ taken over the whole space is equal to 0?

The following excerpt is from Space—Time—Matter by Hermann Weyl, starting on page 101. Among the things I'm not understanding is Weyl's assertion that the integral of $\nabla\cdot(\phi\mathbf{E})$ ...
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1answer
101 views

Why do these 2 formulas about magnetic field conflict with each other?

$\newcommand{\tl}[1]{\tag{#1}\label{#1}}$ Magnetic Field of a current is: $$B = \mu_0 I / (2 \pi r)\tl{01}$$ Magnetic Field of a Moving Charge is: $$B = \mu_0 qv\sin\theta / (4\pi r^2)\tl{02}$$ So I ...
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3answers
61 views

Can we express magnetic field strength similar to how we express electric field strength?

I'm currently studying magnetism and I'm looking to make some connections with electricity, namely how we define the two fields. For the electric field, I know that the electric field strength is: $$\...
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5answers
79 views

Using gauss law to determine field

Let us consider a $+q$ charge and we are trying to find out electric intensity $E$ at a distance $r$ from $+q$.The conventional way is this: We take a gaussian sphere of radius $r$. We know the ...
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Effect on internal electric field on grounding

What happens to internal electric field inside the conductor which is placed in uniform external electric field and conductor's induced negative side is grounded. Explain what happens inside the ...

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