The classical theory of electric and magnetic fields, both in the static and dynamic case. Also covers general questions about magnets, electric attraction/repulsion etc. Distinct from electrical-engineering.

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Water flow in salt solutions contemporary exposed to an electrical and constant magnetic field

When a permanent magnet is held motionless close to a salt solution which already has been exposed to an electrical field a flow in the water will be induced and can be detected by applying some ...
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15 views

Why can xenon gas stay ionised after the “trigger voltage” is removed?

From my understanding of a Xenon flash circuit, a storage capacitor and a trigger capacitor are charged up to about 240V (both with similar RC values, but less capacitance is needed for the trigger ...
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15 views

Trying to give a (non-rotating) black hole an electric dipole

Suppose there is a Schwarzschild black hole. You add positrons to the north "pole" and electrons to the south "pole". From an external observer, objects that you add end up "stuck" to the horizon. ...
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1answer
52 views

Do relativistic electrons have more charge?

Gauss's law tells us that the total electric flux out of a closed surface is equal to the charge enclosed divided by the permittivity. When a charged particle is moving close to the speed of light ...
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2answers
805 views

Why don't photons split up into multiple lower energy versions of themselves?

A photon could spontaneously split up into two or more versions of itself and all the conservation laws I'm aware of would not be violated by this process. I've given this some thought, and a system ...
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17 views

Electric field radiation with moving charge and observation point

I've been working on Chapter 34 of the first volume of the Feynman Lectures on Physics http://www.feynmanlectures.caltech.edu/I_34.html#Ch34-S1. In Fig. 34–3 (reproduced above) Prof. Feynman shows ...
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1answer
48 views

Can a static electric field have a vector potential field?

We know very well that static electric fields have scalar potential fields, and magnetic fields can't have scalar fields, as $$\nabla\times \vec{B}=\mu_0\vec J$$ $$\Rightarrow \int\nabla\times ...
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18 views

What is the pressure equation of an ionized gas?

I have $N$ ${\rm H}^+$ gas molecules in a sealed, electrically insulated container. What equation can I use to accurately calculate the pressure of the gas? It seems to me that $PV = nRT$ will not ...
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1answer
35 views

How to approach proofs in Electricity and Magnitism that involve integrals?

I have read through both Franklin and Jackson's Electromagnetism books and I am able to understand the different proofs involving integrals but when I try to re-derive them on my own later I am always ...
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1answer
35 views

Rigourous Treatment of Antenna Theory/Physics

As a rising senior who has finished his QM sequence but not yet done an E&M/optics sequence, but is about to start a research project that will be a large part antenna design and optimization, ...
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1answer
28 views

Difference in resistance between two configurations

Given a spherical shell of a conducting material with radius $a$, surrounded by a poorly conducting material between it and another conducting shell with radius $b$, you can calculate the resistance ...
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1answer
26 views

RF disturbances produced by transmission power lines

I need a book or paper that contains "the effects of transmission lines on the radio frequency transmission and disturbances". Could you help me find a useful textbook? Thank you
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2 views

What state is needed to model AC 3 phase induction motor?

Suppose I have a regular 3 phase 50hz AC squirrel cage motor of known design. If I wanted to make a model of this motor, would I need to know more than: Angle of rotor Angular velocity of rotor ...
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28 views

What is ultimate AC frequency and phenomena related to it?

Just as in title. What is the top AC frequency physically possible to obtain? And are there (and if yes, what?) phenomena occuring only at large frequencies? I'm thinking about a metallic wire. I know ...
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1answer
61 views

What's the meaning of linear medium in electromagnetism?

I'm studying the book Polarimetric Radar Imaging: From Basics To Applications and on page 31, there's this sentence: In the following, we shall consider the propagation of an electromagnetic ...
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0answers
25 views

Calculating the force applied by an electromagnet on a ferromagnetic object

I know how to calculate the force applied on a magnetic object by an electromagnet at $n$ metres distance using $$F = \frac{(N \cdot I)^2 \cdot k \cdot A} {2 \cdot g^2},$$ but how would one calculate ...
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11 views

Why is it necessary to break symmetry to get magnetoelectric effect in multiferroics?

Spatial or time symmetry needs to be broken for both magnetic and electric to happen in the same material. But how is symmetry hindering the process?
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34 views

Charge distribution on uncharged conducting sphere

I am trying to solve the following problem: A charge $q$ is brought to a distance $d$ from the center of an uncharged, conducting sphere of radius R. What is the charge per unit area of the sphere ...
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8 views

Calculating the Electric Field at the center of an arc [on hold]

A total charge Q is uniformly distributed on a 180º arc of thin, non-conducting rod in a semicircular arrangement with radius a. Calculate the electric field at the center of the arc. I'm not sure ...
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3answers
36 views

How to conserve energy with electrical noise?

If a resistor experiences thermal noise, it will dissipate energy to the environment. But where does the resistor's energy come from? It seems that it will just lose energy until ran out.
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11 views

Change in magnetic field region reduces overall voltage due to change in resistance?

Consider the following diagrams: Diagram(1): A large conductive slab($C$) with resistance ($R$) and region with magnetic field($B$), the conductor moves to the right as indicated with ($v$). ...
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94 views
+100

What are the characteristics of light entering a medium traveling at relativistic speeds?

If I were to spin a translucent disk so that the edge is spinning at .9c and shoot a laser beam at it perpendicular to the edge, what would happen to the light as it travels in one end of the disc and ...
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1answer
36 views

Why in electrostatics is dV=-E.dr but in electromagnetic induction , EMF=+E.dS?

In electrostatics we learned that dV=-E.dr. I understood the derivation which was used to derive this. Now when I have come to Electromagnetic Induction,I see that when there is a time varying ...
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24 views

Expanding Electric Field, Magnetic Field in post-Newtonian Gravitational Potential

I've cross-posted this question from Mathematics since Physics is probably better suited for the nature of the question. I've ...
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1answer
45 views

How (i.e. with what instruments) can one measure electric flux? [on hold]

Supposing we have a charge distribution and some curve $C$ bounding a surface $S$, how does one measure the electric flux through $S$ with practical equipment/instrumentation? Does one use a ...
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1answer
43 views

How does one measure the phase of a wave?

Given an electromagnetic wave of unknown characteristics, is it possible to measure its phase? Or does it always have to be inferred from interference with another wave (e.g. beating etc.)?
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Books on Hall IC? [on hold]

Can anyone suggest a good reading on Hall IC that is used in practicals on magnetism?
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2answers
92 views

Magnetic Force Confusing Paradox

Actually I had posted a very similar question, but I wasn't quite satisfied with the answer so I am posting a new variety again. Imagine an infinitely long wire carrying current $I_1$ from West to ...
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1answer
51 views

Einsteins thought experiment on travelling with a light wave

This might be better suited to the science.history.SE; but I thought I would try here first. Einstein reportedly considered a thought experiment where one considers travelling alongside a light wave; ...
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1answer
68 views

How to prove the following relation $H=\frac{E\times v}{c}$ [on hold]

Using CGS units, how can we prove the following relation $$H=\frac{E\times v}{c}$$ where H is magnetic field, E is electric field and v is velocity
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10 views

What is the role of the Cowling, Pedersen and Hall resistivities (or conductivities) in plasma physics?

The current density $\vec{j}$ can be computed as $\vec{j} = \vec{\vec{\sigma}} \vec{E}$, where $\vec{\vec{\sigma}}$ is the conductivity tensor and $\vec{E}$ is the electric field. This conductivity ...
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3answers
194 views

Why do electrons and positrons exhibit opposite helical motion in a magnetic field?

When you throw an electron through a solenoid, it moves helically around the field lines, as per this schoolphysics illustration: © Keith Gibbs 2013 Then if we were to throw a positron through the ...
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2answers
39 views

Physics of color: why do visible colors absorb all colors except the color itself?

It's funny I cannot answer this question, but I really don't have a very good physical intuition for how color works. I know that sunlight and (say) light from lightbulb is a superposition of all ...
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2answers
67 views

Showing that the magnetic field inside an infinite current carrying cylinder is zero

I'm doing some self studying of introductory physics, and was working a question from a textbook that has several parts. The first few parts asked me to show that the magnetic field of an infinite ...
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1answer
80 views

Why curvature produced by electric field in spacetime is so small?

The electric field due to charge is $E=\frac{Q}{r^2}$. Why is the curvature in spacetime produced by this electric field so small? Let's say we want to calculate curvature(in spacetime) produced by ...
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28 views

What happens if I pass electric current through conductor magnet? [closed]

Good days everybody. My question is as seen at the title. What happens if I pass electric current through conductive magnet? If there's no conductive magnets, can we guess what would happen if there ...
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0answers
4 views

Dipole moment and magnetic power of permanent magmets(circular or disc shaped)

Is any circular or disk shaped permanent magnet has its dipole magnetic moment and if answer is no,then why and how are the behaves as magnetic materials or say that they show magnetic power?
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2answers
28 views

The source and sink phenomenological description of charge - how realistic is it?

I've heard over and over an electron described as a source of the electric field, but that is a misleading term. Source makes one thing of a tap, with a constant flow of something coming out of it. ...
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3answers
125 views

General relativity without curvature?

Is there a reformulation of general relativity without curved space time, just with fields (like classical E&M)? Edit: removed the part about E&M with curvature (multiple posts).
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2answers
46 views

Which photons pass through a circular annulus?

Passing light through a circular sieve: Well, actually, let’s think about radar or microwaves with a wavelength of order a centimeter or two, so you can tailor your aperture, say by etching a silver ...
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How to divert water flow by magnetic field or static electricity or electricity?

Is it possible to make a magnetic or electric plate that prevent hitting water to itself or at least divert it? Which force is most effective, magnetic field or static electricity or electricity?
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as applied to the Dirac delta homogeneous distribution in mantle of a cone [closed]

hello me a problem arises in applying the Dirac delta function in mantle of a cone with a view to seeking load distribution, this doubt is how to find Q so applicable to this type of distribution, ...
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30 views

Electromagnetic Waves and Magnets

Does an electromagnetic wave have an affect on a permanent magnet or on a piece of metal? When light hits a regular bar magnet is there a magnetic push or pull on it? And Does an electromagnetic ...
2
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3answers
58 views

Observing a photon during flight

When I was reading about the double-slit experiment in quantum mechanics, everything seems to make sense in terms of the waves and the interference pattern, but if thinking more about this ...
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2answers
40 views

Energy in conductors with $\vec{E}$-field

The question is deceptively simple. Suppose I have a uniform circular wire in which I have created the a E-field by some mean. We that without the source the electric field should not be there, so if ...
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5 views

What does magnetic flowmeters measure?

What parameter does the magnetic flowmeter actually measure? Velocity of the conducting liquid flowing through it or the amount of conducting liquid directly? The volume of liquid can be calculated ...
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19 views

What is direction of induced current in a rotating rod pivoted at one end in a magnetic field?

This is rod of length l, placed on metallic ring of the same radius as rod's length. This set up is placed in a magnetic field perpendicular to the rod and into the plane. It is very clear that an ...
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3answers
101 views

Can we say that gravity(indirectly) is responsible for motion of electrons around nucleus? [closed]

From Wikipedia But because general relativity dictates that the presence of electromagnetic fields (or energy/matter in general) induce curvature in spacetime From Wikipedia An ...
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1answer
59 views

When to use separation of variables in E&M? [closed]

I'd really like to know if there is a fast way to recognize if separation of variables is the most appropriate way to go about solving a problem. Are there any kind of guidelines for when to use ...
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1answer
58 views

Does a charged particle propagating in free space have a 'self-energy' like term due to it’s interaction with the fluctuations of the quantum vacuum? [on hold]

Does a charged particle propagating in free space have a 'self-energy' like term due to it’s interaction with the fluctuations of the quantum vacuum? (particle-antiparticle pairs popping into and out ...