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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2answers
26 views

Would a magnetic needle standing on it's point on a magnet be more stable than the same needle stood on a non-magnetic surface?

So I was watching MinutePhysics' video 'How long can you balance a pencil?' and it turned out to not be for very long. Would introducing a magnet to the equation make for different results? We can ...
2
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2answers
75 views

Could a civilisation contact us by laser from 50 light years away?

The Kepler Space Mission has discovered over 1,000 planets. These discoveries may increase the confidence of some people that other civilisations exist. That is an opinion issue, and not what I want ...
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0answers
31 views

Reason for strange magnetic ball movement

I was playing with a set of those neodymium magnet spheres and noticed a couple of strange behaviors (which I believe are related so I'm only positing a single question) and I was hoping to get an ...
0
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0answers
13 views

About to purchase a 3d-printed Keppe Motor Kit for art project - what should I test for? [on hold]

I'm about to apply for art-grants in order to purchase a educational student toy called a 3d-printed Keppe Motor Kit. Says on their page "Designed with educators and students in mind".. So.. It is ...
0
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1answer
33 views

Fleming's right hand and left hand rule

Why are there two rules: Fleming's left hand and right hand rules? What is the difference between the two and why can't we use just one rule? Suppose the magnetic field is from right to left and ...
2
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1answer
42 views

Why is the Mixed Faraday Tensor a matrix in the algebra so(1,3)?

The mixed Faraday tensor $F^\mu{}_\nu$ explicitly in natural units is: ...
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0answers
32 views

Verification of Lenz's law in magnetic induction

So the device is a Galvanometer. According to the Lenz's Law, when we take the magnet towards the coil, the pole at the right end, should be north pole and when we take it away, the pole should be ...
2
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3answers
53 views

Why is Kirchhoff's second law commonly used for circuits involving inductivity?

I have often seen in introductory literature, e.g. for the activation process of a circuit with a power source which delivers the voltage $U$, current $I$, resistance $R$ and an inductivity $L$, that ...
-2
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0answers
14 views

Magnetic field due to closed donut [on hold]

How to find magnetic field due to a torroid? Thanx in advance. Im studying for jee and our prof tried to teach it but i didnt understand.help please
-1
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0answers
20 views

Unable to solve cable theory equation correctly [on hold]

First time posting, let me know if I'm in the wrong board. I tried this over on the math board and was redirected here. In my spare time I enjoy reading outside of my field (software development). ...
-1
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0answers
6 views

Magnetic field lines for perpendicular current carrying wires [on hold]

Given two straight current carrying conductors, carrying the same current I kept perpendicular to each other. What would the magnetic field lines look like?
0
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1answer
28 views

Do you know any graphing software for graphing equipotential lines? [on hold]

well, do you know any software for graphing equipotential lines? I only know how to graph straight lines :( Thanks for any information.
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0answers
46 views
+50

Two induced EMF's from separate magnetic fields opposing each other with an odd change in B?

A conductor in case 1 has two separate uniform magnetic fields $B_1$ & $B_2$: The magnetic fields(the blue rectangles are the field regions parallel to the conductor, while X's are the field ...
0
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0answers
21 views

$\vec{E}$-and $\vec{B}$-fields in RCL circuit from Maxwell equations

Consider a basic RCL-Circuit consisting of an ideal resistor, an ideal capacitor and an ideal inductor in series. How do the $\vec{E}$- and $\vec{B}$-fields look like in dependence of the time? I ...
8
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5answers
973 views

Intuitive definition of electromagnetic field

I am curious about the following: Checking about what is an EM field in wiki it says: An electromagnetic field (also EMF or EM field) is a physical field produced by electrically charged ...
-4
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0answers
20 views

how much voltage and current require to pull 5 kg load by electromagnet? [on hold]

I made 600 coil turn electro magnet area of electro magnet 2.235 m square. I want pull nearly 5 kg load distance between load and electromagnet is 40 mm. So how much current and voltage required??? I ...
1
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1answer
61 views

Why are GPS transmitting signals made so weak?

Twice this year, my car's GPS receiver got totally lost. It seemed the cause of this was heavy cloud, (because I can't think of any other reason), and the GPS stayed in "Recalculating" mode, until ...
3
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0answers
8 views

Experiment measuring vacuum permittivity and permeability in high speed

Suppose that we do NOT know anything of constancy of speed of light, to say nothing of special relativity. It is that we acquired a constant speed of light from Maxwell's Equations that we finally ...
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2answers
41 views

Motion of electron and proton in semi infinite magnetic field?

An electron and a proton are moving on straight parallel path with same velocity. They enter a region of semi infinite magnetic field perpendicular to velocity. What will happen there? Will both of ...
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0answers
24 views

effect of earth's magnetic field on period of pendulum [duplicate]

I want to know will earth's magnetic field change period of pendulum if pendulum is made up of- 1. ferromagnetic material 2. paramagnetic material.
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1answer
26 views

Why is there longitudinal conductance in a partially-filled Landau level?

Suppose I consider an infinite, non-interacting (so no FQHE should happen) 2DEG in the magnetic field $\vec B=B\hat z$ with a non-integer filling factor, say 0.13 or whatever. Suppose I apply an ...
0
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1answer
43 views

What makes B-field not be arbitrarily large very close to an electric conductor?

Assume an inifinitely long, straight thin electrical conductor with current I. It follows from Ampere's law that the B-field intensity is proportional to 1/r, where r is the distance from the ...
-4
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2answers
47 views

How to determine the angular velocity of a particle with mass $m$ and charge $q$ in a constant B field? [on hold]

$\textbf{PROBLEM:}$ A particle with mass $m$ and charge $q$ moves in a constant magnetic field $B$. Show that, if the initial velocity is perpendicular to $B$, the path is circular and the angular ...
1
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2answers
49 views

Is the electrostatic field really static? Does thermal vibrations not affect it?

We know that if a conductor has any net charge, the charges reside on the surface. The electric field immediately outside the surface is perpendicular to the surface. But the charged particles, say ...
0
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0answers
16 views

The induced electric field of an infinite current carrying wire

I am given, without motivation, that the induced electric field from an infinite, straight, current carrying wire is parallel to the wire itself. $$ \vec{I} \times \vec{E}_{\text{induced}} = ...
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0answers
25 views

How is ampere defined for alternating current?

Both alternating current and direct current are measured in ampere. But how is ampere defined for alternating current? It cannot be defined from two mutual attraction of two parallel wires carrying ac ...
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0answers
4 views

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 ...
1
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0answers
20 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 ...
0
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1answer
19 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. ...
0
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1answer
67 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 ...
15
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3answers
986 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 think.) I've given this some thought, and ...
0
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0answers
19 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 ...
2
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1answer
57 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 ...
2
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0answers
26 views

What is the pressure of a charged 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 ...
0
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1answer
39 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 ...
1
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1answer
37 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, ...
0
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1answer
30 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 ...
0
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1answer
28 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
0
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0answers
4 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 ...
0
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0answers
29 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 ...
1
vote
1answer
68 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 ...
1
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0answers
26 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 ...
1
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0answers
13 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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0answers
35 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 ...
0
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0answers
9 views

Calculating the Electric Field at the center of an arc [closed]

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 ...
0
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3answers
37 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.
0
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0answers
12 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 ($v$). ...
8
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1answer
176 views
+100

What are the characteristics of light entering a disk spinning at near $c$?

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 ...
1
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1answer
47 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 ...
0
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0answers
25 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 ...