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Results tagged with electromagnetism
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user 159486
The classical theory of electric and magnetic fields, both in the static and dynamic case. It also covers general questions about magnets, electric attraction/repulsion, etc. Distinct from electrical-engineering.
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Changing the location of poles on a neodymium magnet
You could cut the magnet in many smaller magnets and then stack them on top of each another. However, I'm not sure if you end up with a power, because I guess that neodymmagnets tend to fracture.
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What is the relation between electric magnets and permanent magnets?
The energy of a magnetic moment $\vec{\mu}$ in a magnetic field $\vec{B}$ is given by $$E = - \vec{\mu} \cdot\vec{B}$$
There are the following contributions to the magnetic moment of an atom:
The "r …
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Accepted
Magnetic properties of electrically charged metal
I don't think your description is accurate. The magnetic property of a material is not determined by the number of electrons in total, but rather by (a) the number unpaired magnetic moments, and (b) …
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Why are diamagnetic materials repelled when the B field is not changing?
A picture utilizing forces is needed to understand the dynamics of a system. However, if you are merely interested in the "equilibrium-state", an energy consideration might be much simpler.
The energ …
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Does the earth has any electric field as the earth's magnetic field is changing over time?
A time-varying magnetic field can produce electric field.
I think this statement is unclear. Rather: A time-varying magnetic field does produce an electric field. This is one of Maxwell's equatio …
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sin v/s cos-both give the same answer?
As you probably know the sin and cos functions are equivalent, as they are simply shifted by a fixed phase (=angle), $sin(wt) = cos(wt-\pi/2)$. Therefore, we can choose either function.
The key to the …
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Accepted
Why does a magnet not move in presence of an electric field?
The magnetic moments of the electrons are the building blocks of ferromagnets:
The magnetic moment of an atom is associated with the spins of the valence electrons. If we have a single valence electro …
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Accepted
Why are electromagnetic waves attenuated by thick barriers?
Each atom has a well-defined absorption spectrum $\alpha(\lambda)$. The most prominent features of these spectra are the absorption resonances at $\{\lambda_1,\lambda_2, \ldots\}$. However, this does …
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Light, Electromagnetic waves and their physical existence
Physics does not claim to be absolutely true. Instead, it merely claims that it is describing nature. Hence, even if two models/theories are inconsistent with each another, both can still be called ph …
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How to approximate electromagnet-magnet interaction
If you are interested in the static problem, you could use the following steps:
Use Biot-Savart's law to calculate the magnetic field $\vec B(x,y,z)$. Use a grid to obtain the field at different posi …
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Fourier Optics - Why is polarization omitted?
If we assume implicitly, that the polarisation is constant, we are allowed to skip this detail in or description, because the result does not change. However, if we assume that different polarisation …
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Magnetic potential and magnetic field assumptions
I guess an example helps: So let's assume a circle of radius $R_0$ in the $xy$ plane (at the origin) carrying the current $I$. Now calculate the B-field at some point $(x, y, z)$. Using spherical coo …
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If time-varying electric and magnetic fields create each other, how come they are in phase?
As Fedor pointed out, the Maxwell equations describe the dependence between E and B fields. However, in order to answer your question, we can simplify them. So consider the simple relationship
\begin{ …
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Accepted
Is magnetic potential vector due to the magnetic field or energy stored in magnetic field?
For me, the magnetic vector potential $\vec A$ is the fundamental quantity, from which the magnetic field $\vec B = \vec \nabla \times \vec A$ and the magnetic energy $E = - \vec \mu \cdot \vec B$ is …
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Why is there a cross product in Biot-Savart law?
The physics behind the cross product is the empirical observation, that the magnetic field "curls around" the wire. Nobody is able to tell us why this is the case -- it's the way nature does it. Thus, …
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