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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1answer
17 views

Electric field in space created by intersection of spheres of charge

I am trying to calculate the electric field in space created by a body assembled by the intersection of 2 spheres. The upper sphere, its center is at $\frac{d}{2}\mathbf{\hat{z}}$ with radius $R$ and ...
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0answers
25 views

How does non-constant conductivity change surface charge on a wire?

Current density is equal to conductivity times electric field. Therefore flux through a cross section of a wire is equal to current over conductivity. Current has to be constant along a wire. This ...
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1answer
29 views

Can we generate electric current by injecting electrons into a copper panel

Suppose I take a vacuum tube and accelerate electrons in it by electric fields then collide it on a copper plate. Will the electrons then go inside it and generate an electric current by putting a ...
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0answers
30 views

Electric field in a hollow object

I am currently visiting a course about electrodynamics. In my last lecture it was said that if a hollow sphere is inside of a bigger sphere, but only in the bigger sphere there are charges, the ...
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1answer
29 views

Does the electric field inside a circuit cause a potential drop with distance?

We know that when the system reaches steady-state(current does not change with time),the electric filed inside the circuit is constant. In many textbooks and lectures,professors make a graph like this ...
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0answers
29 views

How can I choose my desired direction in which the electrons travel?

If I take a circular vacuum tube (like a particle accelerator) and try to accelerate the electrons in it with a bunch of magnets and like charged panels to repel or attract the electron in it and ...
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1answer
42 views

Can we create a electric field without actually using a battery or power source?

Can we create an electric field without actually using a battery or a source of electricity? Like a take 2 panels, one is positively charged and another is negatively charged and put them parallel to ...
2
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1answer
54 views

Why doesn't the potential drop as a $E=\nabla V$ inside a circuit when there is no resistor?

Considering that an electric field exists outside a battery and inside a circuit, shouldn't the potential drop while we move along the wire even if there is no resistor ($E=\nabla V$)? I am asking ...
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2answers
78 views

Why is there electric field OUTSIDE a battery?

Correct me if I'm wrong, but a battery's electric field is like an electric field of a capacitor consisting of two parallel plates. But we know that the electric field outside the two plates is zero. ...
2
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1answer
42 views

Can we depict the electric field lines between three or more charges?

Last year we studied in school electric field that was created around charges and we were showed how to depict the electric field lines for one charge or between two charges. Then i wondered how would ...
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2answers
55 views

Finding net magnetic and electric force on charged particle [closed]

This is from my textbook, it is not an assigned problem, but I want to understand. It says: Consider the situation in the figure, in which there is a uniform electric field in the x direction ...
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1answer
22 views

Force on a dipole

The force exerted by an electric field on a dipole is : $$(\vec{p}.\vec{\nabla})\vec{E}$$ but how exactly do I develop this ? Is it : $$p_x\frac{\partial E}{\partial x}\vec{e_x} + ...
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1answer
26 views

Which is the right sign convention for the potential difference?

The circulation of the electric field gives the potential difference, but is it : $$V_B-V_A = \int_A^B\vec{E}.\vec{dOM} \hspace{1.5cm} (1)$$ or $$V_B-V_A = - \int_A^B\vec{E}.\vec{dOM} \hspace{1cm} ...
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1answer
37 views

Electric field created by a uniformely charged, infinitely thin, straight wire of infinite length

Using Gauss's law, I find that the expression for this field is : $$E(r) = \frac{\lambda}{2\pi r \epsilon_0}$$ where $\lambda$ is the line charge density. However, when I try to use the direct ...
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0answers
27 views

A flat ring and electrical field

Question: A flat ring (inner radius $R_0$, outer radius $4R_0$) is uniformly charged. In terms of the total charge $Q$, determine the electric field on the axis at points a) $0.25R_0$ ...
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1answer
19 views

currents in an isolated metal exposed to an alternating uniform electric field

For example, let's look at a metal sphere between a capacitor's (infinite) plates. Let's run an AC current through the capacitor, resulting in an oscillating electric field. The charges will move in ...
0
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1answer
53 views

Gauss's law and superposition for parallel plates

Two large, flat metal plates are separated by a distance that is very small compared to their height and width. The conductors are given equal but opposite uniform surface charge densities +- ...
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2answers
43 views

Wouldn't $D = \epsilon E$ mean that a higher permittivity constant gives a higher electric flux? (And what exactly is the displacement field?)

A quote from the Wikipedia page for Permittivity: More electric flux exists in a medium with a low permittivity (per unit charge) because of polarization effects. This makes sense to me. My ...
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2answers
188 views

Confused about Gauss's Law for parallel plates

I am having trouble understanding Gauss's Law. Suppose we wish to find the electric field strength between two parallel plates with charge density $\sigma$. I know it should be ...
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2answers
52 views

Calculating the electric field of an infinite flat 2D sheet of charge

I was trying to calculate the electric field of an infinite flat sheet of charge. I considered the sheet to be the plane $z=0$ and the position where the electric field is calculated to be ...
0
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1answer
40 views

Given a Magnetic Field vector, what is the Electric Field, charge density, & current density?

I tried searching for this before having to ask, so please forgive me if I missed a previous question similar to mine. This is a Grad class, so I may be unnecessarily too careful in not assuming ...
0
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1answer
41 views

Fields and the way they should be looked at

When I think about the electrostatic interaction and interaction of charged particles having uniform velocities sometimes I do find it giving rise to a picture of superluminal communication which ...
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0answers
20 views

Resistance of depletion region

The ideal diode equation is : I=Io[exp(qv/kT)-1]. My question is when we want to represent this ideal diode, it will be represented by a resistance of depletion region right? but is this resistance ...
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2answers
26 views

Is the following thought experiment about two charges correct?

Let's say I put a charge at a point in space for a long enough time. During this time interval it has set up the electric field in the space. Then I put another charge in the space. Since the ...
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1answer
21 views

$E \times B$ drift plasma physics

Do you need to have an electric field in order to have an $\mathbf E \times \mathbf B$ drift? I'm confused because it's seems that there is an induced E-field from the charge separation due to forces ...
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1answer
15 views

Non-zero potential measured on the surface of an insulator

After driving a screw into an alumina firebrick and applying a 5kV potential, I measured a ~4.5kV potential using a high voltage probe at other locations on the brick surface. Firebrick is generally ...
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3answers
28 views

Resistance of capacitors

Please I would like to know how the resistance of the plates of a capacitors work? Is it the same as a resistor? If yes, is there electric field inside the plates like inside a resistor?
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1answer
53 views

Calculating flux of axisymmetric electric field through a sphere [closed]

The following problem and its solution is taken from I. E. Irodov's book basic laws of electromagnetism : I do not understand how the fact that field is axisymmetric leads to the conclusion that ...
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0answers
27 views

Motion of charge particle under electric and gravitational fields

I am working on one experiment in which the charged particle falls under the effect of gravity and passes through the electric field in between. I want to know what is the charge of the particle? ...
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2answers
62 views

Using Electric Potential to Float an Object

I've been trying to answer the following question but I'm stuck at one step. The question essentially states that a magician is trying to perform a "floating objects" act, for which she has a thin ...
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0answers
27 views

Fresnel equations of S and T waves and Isofrequecy Curves: Feeling confused

First of all sorry for my (probably) bad english. I've been studying propagation of light in anisotropic media from the Born and Wolf and from Landau "electrodynamics in continuous media" and I'm ...
2
votes
1answer
47 views

Why does a conductor shield its inside from its outside, but not vice versa?

A point charge outside a hollow conducting sphere will produce no field in the hollow interior: the metal shields the interior. But a point charge inside the hollow interior will produce a field ...
0
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1answer
19 views

How to calculate the electric energy caused by eletrostatic field stored in a region, given $V$?

I have problem in apply the rules to find the energy stored in free space here is the problem Find the energy stored in free space for the region $$0.002<r<0.003m,\quad ...
0
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1answer
67 views

Electric flux of a closed surface, $\Psi = Q $ or $\Phi =\int\vec{E}\cdot d\vec{A}$

I have problem with the equation of electric flux. I use one book of fundamental physics and another book of electromagnetic engineering; the two of them give different equations for electric flux. ...
0
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1answer
45 views

Electric field, special relativity, and charged particle

Given a uniform electric field in the $z$ direction and an observer moving at constant $v$ in the $y$ direction, how you would describe the motion of a charged particle that start at rest in the ...
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2answers
24 views

Are electric fields present in electrically neutral bodies?

In most scenarios I have seen, an electric field occurs when a body has an unbalanced net charge. Are electric fields present in electrically neutral bodies?
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2answers
65 views

Electric Field from charged sphere within another charged sphere does not reinforce?

Lets say I have a positively charged conducting sphere of Q. The electric field outside the sphere is $$E = \frac Q{4\epsilon\pi r^2}$$ Now suppose this sphere is enclosed inside another hollow ...
1
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1answer
99 views

How do electrons distribute themselves along a wire attached to one pole of a battery?

Let's assume we have an electrochemical cell, like an AA battery. We attach a long straight wire to the negative terminus of the battery, the other end of the wire extends right away from the battery ...
1
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1answer
66 views

Apparent Violation of Energy Conservation in an Electromagnetic system

As shown in the figure a beam of EMW pulse is propagating towards a nearly point charge.Here if we calculate the total energy of the system by the equation mentioned in photo - we get that the total ...
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1answer
33 views

Manipulation of one electromagnetic field by another

How is it possible for one electromagnetic field to alter, or control, another electromagnetic field. I am thinking specifically of manipulation of the endogenous fields that are related to brain ...
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1answer
46 views

How to convert EM fields to EM waves?

How a body producing electricity and magnetic fields become a body radiating electromagnetic waves?
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2answers
127 views

Proof that the electric field is conservative

I was told a proof that the electric field was conservative (without using $\nabla$) which used a point charge and showed the following: $$w.d.=\int_c{\vec F \cdot \mathrm{d} \vec l}=\int_c{\vec ...
3
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1answer
160 views

Need of small charge in definition of electric field?

Why do we need infinitesimally small charge in definition of electric field? Since the test charge cannot exert force on itself, F on test charge will not change whatever the value of test charge q ...
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2answers
180 views

Electric field around two charged hollow cylinders

There are two hollow cylinders with same lengths "l" as shown in the figure below. The smaller inner cylinder is negatively charged. The outer one is now induced to become positively charged. I am ...
0
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0answers
32 views

Probe/Sensor-design for pulsed electromagnetic field

So I have a wire/coil, acting as a sender, which has a pulsed signal as described below. I would like to build a sensor/probe that can detect the electric field at a distance, where the primary goal ...
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0answers
33 views

Can electromagnetic fields be measured from a distance?

I know that direct measurements of electromagnetic fields can only tell information about the field near the probes, but I am curious if there is a way to measure the electromagnetic field in a not ...
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0answers
24 views

Why is there no charge in a capacitor connected to one battery pole? [duplicate]

Here is a very simple drawing of a battery pole and a capacitor plate connected by a wire (exaggerated in thickness). The question is, why is the capacitor not being charged? But as you will see ...
2
votes
1answer
223 views

Electric Field of Hollow Cylinder

Let's say we have a hollow cylinder with a charge $q$, radius $r$ and height $h$ as in the figure below. I am trying to find the electric field perpendicular to the surface of the hollow cylinder. I ...
2
votes
1answer
86 views

Virtual Photon transmission speed of a Static Electric Field?

In the case of a non-accelerating point charge "A" of stable velocity, its static field is treated as though it is instantaneously present at a distance, i.e. a second point charge "B" will react to ...
3
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1answer
30 views

Meaning of potential in a discharging capacitor

I am dealing with this thing I cannot figure out. When a capacitor is discharging, the electric field inside it varies with time so we cannot perform the line integral to determine the potential ...