# Tagged Questions

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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### Is my understanding of electric fields accurate?

Could someone please help me and let me know if the statements below are any accurate? I am struggling trying to understand what electric fields are and I could really use some help! An electric ...
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### Why does the Electric Field of a dipole have no x component

According to the solution $2E\sin(\theta) = E_{net}$. I understand how the dipole works but I don't understand why the x component would be 0?
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### How to approximate trajectories and movement of two oppositely charged particles?

Imagine a single, stationary charged atomic ion, say a Lithium anion or cation (Li+ or Li-). Now imagine another a single free, oppositely charged particle--perhaps an electron or Hydrogen ion ...
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### Why is the electric field highest in regions of highest resistance?

I know Kirchhoff's law and that current must be constant. But what exactly is the phenomenon, from first principles, that causes the electric field to be stronger in a region with lower carrier ...
56 views

### Change in Potential energy moving toward line of charge

I'm analyzing the energy involved with charges moving in an electric field and I'm getting caught up here and I must be missing something. So given that an infinitely long line of charge produces a ...
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### Electric Flux through metal plate by uniformly charged wire

Suppose a long uniformly charged wire is placed parallel to a thin uniform metal plate of length l and width $w$. Distance is $r$. Then how to calculate the electric flux through the plate if the ...
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### Electric field of two infinitely long and thin, straight wires

I know the formula of the electric field, however: suppose that we put two infinitely long and thin, straight wires symetrically into the coordinate system, so that y axis is between them. Now ...
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### Calculating voltage in piezoelectric material

The piezoelectric constitutive law is defined by the two equations: $$S=s T+dE\\ D=d T+\epsilon E$$ $S$: Strain. $T$: Stress. $E$: Electric field. $D$: electric charge-density displacement. ...
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### Why electric field inside charged conductor is zero in the electrostatic case?

I am trying to understand the idea (or the fact) that most books introduce which is about the electric field inside a charged solid conductor Books tell that the field has to be zero everywhere ...
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### Potential and Electric field

I'm trying to find the electric field from the potential and vise-versa but I'm having trouble I know the electric field of a ring with radius a and charge Q to be E=\frac{Qx}{4\pi ...
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### How can equipotential planes differ in potential in an uniform field?

I'm trying to solve an exercise that asks me the field strength of an uniform electric field where equipotential planes differ by $1\ \mathrm{V}$ and are $2.5\ \mathrm{cm}$ apart. First of all, I ...
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### Electric field due to a charged conductor

I have this grave confusion that I have been having since a while. When we calculate the electric field due to an infinite plane sheet of charge then the answer comes out to be $σ/2ε$. In this case we ...
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### Why does the potential difference between two charged plates increase as they move further apart?

Suppose a uniform electric field $E$ exists between to oppositely charged metal plates (one is positively charged and one is negatively charged). If the plates move apart, and the charges on each ...
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### Calculating the amount of charges for an object that is electrostatically induced

Induction is one of the ways to get an object electrostatically charged. While positive charges accumulate on one side, negative charges accumulate on the other side for an object in an electric ...
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### How can a black hole have a charge? [duplicate]

Under current particle theory, the four fundamental forces use a force-carrying particle. The particle for electromagnetism is the photon. By definition a black hole is a mass from which light can ...
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### Electric field parallel to a hollow cylinder (outside) [closed]

Having trouble with a question my lecturer posted me. A thin-walled hollow circular glass tube, open at both ends, has a radius R and length L. The axis of the tube lies along the x axis, with the ...
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### Electric field in a conductor

Is it always true that the electric field in a conductor is zero? What would happen if I put a very big charge inside an ungrounded hollow conducting sphere like this image? The charges inside the ...
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### Understanding the differences and applications of some electrical equations

In preparing for the AP Physics 2 test tomorrow, (the first year this test is being offered, so this material is not easily searchable), I've been doing some reviewing of the equation sheet and trying ...
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### How electric field can be less than force per unit test charge?

I have been going through some physics objective questions and struck with this one Q:A negatively charged metallic ball is supported on a rigid insulating stand. We wish to measure the electric field ...
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### dipole field on axis twice the field on perpendicular bisector

Why is the dipole field on axis twice the field on perpendicular bisector? For the perpendicular bisector: Lets assume -q is right from of the origin and +q is left from the origin, both a distance a ...
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### Do the relations between E/B and D/H contain higher order multipole terms?

Jackson writes in section 1.4 (third edition) that \begin{align*} D_\alpha &= \epsilon_0 E_\alpha + \left(P_\alpha - \sum_\beta \frac{\partial Q'_{\alpha\beta}}{\partial x_\beta} + \ldots \right) ...
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### Electric field or static electric field around a plugged-in lamp cord (when lamp is not turned on)?

When an electrical cord from, say, a lamp, is plugged into an AC wall socket, I'm aware that an electric field forms around the entire length of the cord and even before the lamp switch is flipped on. ...
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### Electric potential at midpoint?

I understand that if you assume the field is uniform between R and S then you can use E=V/d to get E=(30-20)/(0.5)=20Vm^(-1), so the answer is C (which is correct according to the mark scheme). But ...
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### Is there an electric field in the direction of a uniform current?

In an infinite plane where uniform current is passing through,is there any electric field? Because i know that charge produces an electric field but in a uniform current and because it is an infinite ...
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### Calculating the charge of weights on a rod based on it's movement in an electric field

I've got a problem from my physics course which I am a little stuck on. A dumbell consisting of two identical masses m=5.8 kg attached to the ends of a thin (massless) rod of length a=0.4 m that ...
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### How to calculate charge on an internal and external surface of a conductor, due to an internal charge

Having a bit of trouble with a question our first year lecturer has given us to think about. Say we're given a hollow cylinder (the hollow region is central and spherical), made of a conducting ...
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### Is there a difference between Electric and Electrostatic Field?

Is there a difference between Electric and Electrostatic Field? All I know is that they both represented with same law suppose we have a Charge placed at the Origin: ...
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### Why do electric field lines start and end at 90 degree at the surface of a conductor? [duplicate]

There is one property of electric lines of forces which states that: Electric field lines start and end at 90 degree at the surface of the conductor. But why is that so? Is there any proof for ...
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### Electric field due to a finite line charge [closed]

I was wondering what would happen if we were to calculate electric field due to a finite line charge. Most books have this for an infinite line charge. In the given figure if I remove the portion of ...
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### How do I choose the right value of $r$ to find where the electric field is zero?

Sorry for the long question. I'm having a difficult time trying to explain my confusion. I have a positive point charge$\ Q_1 =+q$ at the origin and a negative point charge $\ Q_2 = -2q$ at $\ x=2$ ...
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### Electric field on conductor surface

Having searched around I came to the conclusion that the electric field on the surface of a charged conductor is undefined as in there is a discontinuity but is there a way to explain it intuitively ...
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### Can we create plasma with other things except gas?

In my school book its written on how plasma is created and it is said that we can create plasma by ionizing a gas but i have heard that plasma can be created even from liquids like water and also from ...
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### Removing the charge from charged object

let's say I have an object with an electric charge Q. I'm not sure if I can remove charge 2Q from it so it will become negative (-Q) or I can't do it. To be specific I have this example: There are two ...
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### Electric field due to a uniformly charged FINITE rectangular plate

I was teaching kids about how to find electric field using the superposition principle for continuous charge distributions, I thought may be I should derive the formula for electric field due to the ...
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### Considering this hypothesis…is charge really quantized? [closed]

[If anything goes against any mathematical or physical rules please let me know. I am a first year undergraduate student perusing a joint major in mathematics and physics so I do not have a complete ...
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### Why does a real/virtual photon interact only with charged particle?

A photon is the force carrier of an electromagnetic wave and it consists of an electric and a magnetic field propagating through space at the speed of light in vacuum. It exhibits wave-particle ...
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### Special relativity, electromagnetic fields, charge and Q

Is it true, were Coulomb's constant k to be several orders of magnitude smaller, that there would be no (or increasingly negligible) magnetic fields generated by moving charges? The reason being the ...
334 views

### Why does a voltmeter give a positive reading for a path in the same direction as the electric field?

Straight from my textbook: If the direction of the path from initial location to final location is the same as the direction of the electric field, the potential difference is negative. Yet a ...
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### Why is the electric field operator normalized by a volume?

I came across the following definition of the electric field operator: But I am not sure what this $V$, the "volume of a box", is about. It seems to enter the discussion in order to have standing ...
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### Find the electric field of light due to an LED [closed]

This is a JEE mains question which neither me, nor any of my teachers can figure out. Help me here. "A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the ...
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### Expanding the H and D field in orthogonal modes

Currently I am doing my bachelor thesis on the behaviour of Q-factors in 3D microwave cavities. One step in that process is to approximate the behaviour of the 3D cavity by comparing the cavity to an ...
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### When a thermal source emits electrons how are the spins of this electrons are aligned?

This question refers to the moment of the emission. Suppose the electrons get emitted in a small beam. Are the spins of the emitted electrons in the moment of their emission are showing all in ...
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### Electrical breakdown due to a charge

Electrical breakdown occurs due to the fact that the magnitude of electric field of a charged object is above the electrical breakdown limit of the insulator that surrounds the charged object. ...
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### Would a spinning, evenly charged sphere generate a magnetic field?

I could see how it would go either way. On the one hand, there IS moving charge; on the other hand, it is not discernibly moving.
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### Why is it possible to define a potential difference in a wire that carries a steady current?

My book introduces $\nabla\times E = 0$ as the condition for an electrostatic field, which is what makes it possible to define a potential difference between two points. As far as my present ...
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### Uniform Electric Field

I was going through the first chapter in Resnick Halliday related to electromagnetism and then I came across something called a uniform electric field. It was written that "If E is uniform (that is, ...
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### Why does a field-effect transistor (FET) with wrap-around gate work at all?

In the recent years several publications have presented field-effect transistors (FETs) that are based on semiconductor nanowires with a gate electrode that is wrapped around the whole nanowire ...
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### Electric Field At Centre Of Non Uniform Ring

In the above solved example why only the cos components have been taken for calculation of electric field at centre ? Why not the sine components ? BTW in case you say that the sine components ...
Let us consider a charged particle moving with uniform velocity $v$. We know that the EM field due to it has some momentum too. If the mass of the particle is $M$, then the momentum of the particle is ...