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.

learn more… | top users | synonyms (6)

0
votes
0answers
7 views

Frequency of Electromagnetic Radiations/Waves?

"A charge that is accelerated will produce variable electric and magnetic fields. These are electromagnetic waves. If the charge oscillates with a frequency f, then the resulting EM wave will have a ...
6
votes
3answers
136 views

How do electromagnetic waves carry energy?

Its said that electromagnetic waves carry energy. Is this because these waves are made up of electric and magnetic fields which can cause changes to the stuff that falls with in their range? Is that ...
-1
votes
0answers
15 views

Two charged conducting spheres when placed in contact with each other

What happens when two charged conducting spheres of different radii are brought in contact with each other. How does it affect the charge distribution and field lines of spheres?
2
votes
0answers
22 views

What experiments confirmed Poynting's Theorem?

Actually, I have two related questions. The fist is the above question. The second is, what experiments confirmed that $\varepsilon_0\left(\frac{E^2}{2} + c^2 \frac{B^2}{2}\right)$ is the ...
0
votes
1answer
20 views

Why is the electric field homogenous inside a circuit?

In a circuit between to poles of a battery, there is an electric field accelerating the charges in the wire towards lower potencial (but due to resistivity they only travel at drift velocity). Is ...
1
vote
1answer
178 views

How do you derive Fleming's left hand rule?

How do you derive Fleming's left hand rule? What is the theoretical explanation for the directions of the magnetic field, current and the force on the current for being oriented in that way relative ...
0
votes
1answer
19 views

Biot–Savart law for a finite wire or the center of a square coil

I need to find the magnetic field inside the center square of a coil (I think this is the name, I'm translating, but if not, I'm talking about a loop of a wire, just 1 turn) of side $50cm$. So, I ...
0
votes
0answers
9 views

The radiation intensity considering dipole, quadrupole and magnetic dipole parts

In page 204 and page 205 of the book "The Classical Theory of Fields" written by Landau and Lifshitz, there is this sentence In averaging the square of the magnetic field, all the cross-products ...
0
votes
3answers
102 views

Can we use magnetic energy to produce electricity?

Magnets attract each other with a force (magnetic force), because they possess magnetic energy. My question is, is there any way, by which we can convert that magnetic energy into electrical energy? ...
0
votes
1answer
38 views

Ampere's law and Stokes' Theorem for current density

In both Griffiths and Jackson, Ampere's Law (or conversely the curl of the magnetic field) is derived by applying Stokes' Theorem to the surface integral of the current density J. The argument relies ...
2
votes
1answer
74 views

Simple Explanation of Kondo Effect

Does anyone have a simple explanation of the Kondo Effect? (i.e. a simple physical picture + maybe equations to think of?) My current understanding is this: If we consider an electron scattering ...
0
votes
1answer
27 views

Principle of capacitor

It is said that second conductor reduces the potential of fist conductor and hence increases charge taking ability of first conductor My confusion... As per my limited knowledge it is electric ...
0
votes
1answer
27 views

Magnetic force on a charged particle doesn't affect total energy

So there's this sentence in a book I am reading. It states "When a charged particle is placed within a magnetic field, despite the magnetic force acting on the particle, there will be no change in the ...
0
votes
1answer
468 views

How to calculate flux density in a toroidal CT that has an electrical line pass through the center?

I have seen the Biot–Savart equation, but I don't know how to apply it. Does the conductor length need to be considered finite and equal to the core length, or will the calculation be for a conductor ...
-1
votes
0answers
29 views

Light and Magnets

Magnets affect EM field, tried that, know what it does. However, if light is a form of electromagnetic field, why is it not affected by a magnet?
2
votes
2answers
552 views

What limits the maximum sustainable surface charge density of a sphere in space?

Suppose I charge a sphere and leave it in vacuum for 10 years. After that time, I want its surface charge density to be in the order of 10^5C/m^2. Would that be possible? Would it depend on the ...
0
votes
0answers
15 views

What is the energy density of a spinning orbiting ball of uniform mass with surface charge?

What is the energy density of a spinning orbiting ball of uniform mass with surface charge? I know that all the energies involved are mass-energy, spinning energy, orbiting energy, electric energy ...
-5
votes
1answer
65 views

What is exact difference between gravitational force and magnetic force? [on hold]

I've read that gravitational force is due to mass only and magnetic field is due to moving charged particles. But my question is: what are other difference between them? Can we set up a small ...
0
votes
0answers
20 views

How Do I find the Thermal increase of a ideal gas flowing through a magnetic field? [on hold]

I am thinking of turning dissociated 2H_2 and O_2 into plasma by forcing it through a electromagnet field. what are the equations to determine the thermal energy added to the gas. I'm thinking to ...
-1
votes
3answers
30 views

Frequency of other light in white light [on hold]

I have this question in mind because I read that the frequency of light depends only on the source of light. If we consider a source of white light then it emits light of different colours also. Then ...
0
votes
0answers
28 views

Electromagnetic Field caused by accelerating and oscillating charge particles?

Will accelerating and oscillating charges will cause EM waves of different shapes ? As EM waves are always shown as sinusoidal Electric and Magnetic Fields perpendicular to each other. Does it mean ...
20
votes
4answers
9k views

Is Biot-Savart law obtained empirically or can it be derived?

Well, there's already a question like this here so that my question could be considered duplicate, but I'll try to make my point clear. Is there a way to derive Biot-Savart law from the Lorentz' Force ...
0
votes
4answers
137 views

Calculating the magnetic force on a charged particle

For my homework I'm supposed to answer the following: Now consider the example of a positive charge q moving in the xy plane with velocity v⃗ =vcos(θ)i^+vsin(θ)j^ (i.e., with magnitude v at angle ...
6
votes
1answer
251 views

$U(1)$ 5-dimensional Kaluza-Klein topological defects

Five-dimensional Kaluza-Klein theory is well-known to predict that the electromagnetic field can be described as a curled additional dimension over four-dimensional spacetime. That is, you only need ...
1
vote
2answers
31 views

Finding the speed of electrons in a magnetic field

So I'm trying to solve this problem in which an electron beam is "drawing a picture" on a TV screen. The electrons are accelerated to a voltage of $3 kV$ by wire coils and are then directed to ...
2
votes
3answers
4k views

Artificial planetary magnetic field

I wonder how difficult it is to create an artificial planetary magnetic field with generators? What power they would need? The question is inspired by thinking about possible colonization of ...
3
votes
3answers
80 views

Field equations of a given action

Provided an action: $$S[A_\nu] = \int\left(\frac{1}{4\mu_0}(A_{\gamma,\mu}-A_{\mu,\gamma})(A_{\zeta,\alpha}-A_{\alpha,\zeta})\eta^{\gamma\zeta}\eta^{\mu\alpha}+\frac{1}{2}\nu^2A_\mu A_\gamma -\beta ...
1
vote
1answer
258 views

Explanation of force amplification inside a solenoid

For a system being actuated by a motor, the force can be amplified by gearing. The energy is being used for force instead of distance, so it produces more torque but moves slower. For a system being ...
0
votes
0answers
20 views

Charge Magnitude Based on Isoline Spacing

Suppose we have two positive charges of unknown magnitudes. We are given the isoline map (the equipotential lines) for the two-charge system. One has isolines more "squashed together" (more closely ...
1
vote
0answers
22 views

Wire with current in magnetic field $\vec{B}$has force $\vec{F_1}$. When rotated, $\vec{F_2}$. Find $B$ [on hold]

I have the following question: In a wire with $10cm$ there is a current $4A$ going 'upwards' in the $z$ axis. The force over this field, under a constant magnetic field $\vec{B}$ is $F = -0.2\vec{i} ...
2
votes
4answers
556 views

Induced EMF of a rectangular loop should be zero?

Considering the shape of a rectangular loop in a changing magnetic field: The induced $\epsilon$ would be zero? Since a rectangular loop is a combination of wires in series to create such a shape. ...
1
vote
1answer
44 views

Magnetic monopoles gauge theories

I'm quoting 't Hooft: "[...] Locally stable field configurations may exist that have some topological twist in them [...].Careful analysis of the existing Lie groups and the way they may be ...
1
vote
1answer
60 views

Hamilton's equations of motion on Dirac's formalism

I'm having several doubts about the procedure proposed by the Dirac-Bergmann algorithm in order to get the correct equations of motion of electrodynamics (Maxwell's equations). Suppose I've already ...
1
vote
1answer
31 views

Is there any electric current in a continuous medium of moving charges?

Suppose that unlike in real life where charge is carried in fixed discrete chunks like electrons that one has a continuous fluid in a bottle that carries charges. Suppose that the fluid is stirred in ...
7
votes
5answers
414 views

Can you deduce absolute motion through magnetism? [on hold]

Trying to understand magnetism I stumble into this example: Suppose there are two electrons travelling side by side in deep space (say, between Mars and Jupiter) at 1 cm distance at .99 c. In this ...
9
votes
2answers
756 views

Do stars remain electrically neutral? [duplicate]

How electrically neutral do stars remain through their lifetime? As an example, I could imagine processes such as coronal mass ejections leaving the Sun in a slightly charged state. Are there such ...
1
vote
0answers
43 views

Electromagnetic waves and photons? [duplicate]

Electromagnetic waves are photons or photons cause electromagnetic waves ? Its said that when charges are accelerated we get electric and magnetic field that carries energy but then they say that this ...
1
vote
0answers
24 views

Why the motion of rotating magnet doesn't stop if we use a superconducting wire?

I would like to know why magnets rotated,wouldn't stop their motion if we place a superconducting wire as said by William Beaty at MadSci Network.
0
votes
2answers
284 views

Domains of electromagnets

I know that magnetism is due to the alignment of domains of a magnetic substance. Due to this reason, an iron bar may be magnetized by stroking it with a permanent magnet such that its domains are ...
3
votes
2answers
78 views

Can bending spacetime produce electromagnetic fields?

Let's say that we can somehow bent spacetime, can this produce electromagnetic fields? or EMF can only be emitted from charged particles of matter?
1
vote
1answer
151 views

Spherical magnet inside a solenoid

When passing a bar magnet through a long solenoid why is it that the induced emf when the magnet is in the middle of the solenoid is zero? And if a spherical magnet is put inside the solenoid, will ...
0
votes
2answers
61 views

Electromagnetic Radiation and Communication!

I read that the accelerated charges create electromagnetic field/spectrum which consists of following different waves: gamma, X-rays, ultraviolet, visible light, infrared, microwaves, & radio ...
0
votes
2answers
3k views

Potential energy from opposing magnets repelling each other with a gap of 1 mm

I have two powerful rare earth magnets, that are separated by a distance of 1 mm. I applied energy to bring them closer to each other, hence increasing the potential energy. Now, when one of the ...
0
votes
1answer
389 views

Voltage across an inductor contradicts Lenz's law?

Imagine a simple circuit consisting of an alternating current source connected to an inductor. Assume they are connected in the following fashion: AC source - terminal A - Inductor - terminal B - AC ...
0
votes
2answers
38 views

Polarized light from any suface?

From a textbook I read something like this: "When sunlight is reflected from a horizontal surface, the plane of incidence is vertical, and the reflected light contains a preponderance of light that is ...
1
vote
2answers
712 views

Can we increase the magnetic flux for a permanent magnet?

When we pass current to the permanent magnet does its magnetic flux, magnetic property of attraction and repulsion increases? if possible Is there any other way for increasing the magnetic flux?
0
votes
1answer
477 views

Coercivity of a ferromagnetic material?

I understand that coercivity is the field/force required to demagnetize/magnetize a ferromagnetic material. What if we had two opposite magnetic fields of different strengths values H acting on the ...
1
vote
0answers
27 views

Geometric Algebra formulation of EM in nonuniform dielectric media

Normally, there is a straightforward formulation of Maxwell's equations in free space under the GA framework, which reduces to (picking the right units): $$ \nabla F = \mu_0 J $$ with some ...
0
votes
3answers
934 views

Understanding magnetic force on charged particle

if we put any charged motionless or static particle in the constant magnetic field, then why does it don't feel a magnetic force? Mechanism by which electric and magnetic fields interrelate I have ...
1
vote
0answers
39 views

Can a lightning strike cause your car to not run? [migrated]

If lightning strikes a tree in your yard and your car is close by, can this cause your car to not work properly? I had an employee call in stating that lightning struck a tree beside their mobile ...