Questions tagged [electromagnetism]
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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Friction and electromagnetic force
What is the relationship between friction and electromagnetic force? At microscopic level, how does electromagnetic force cause friction?
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Dipole antennas and the $B$ field
A dipole antenna responds to the electric component of a EM wave. Does the magnetic component of a EM wave have any effect on the performance of a receiving dipole antenna?
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Is the Potential Energy just a bookkeeping device?
It is said that if the space is homogeneous then momentum is conserved. But I've been thinking in the following situation:
Consider a parallel plates capacitor. In between the plates there is a ...
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Is magneto-optic Kerr effect discernible for material with natural optical activity?
Magneto-optic Kerr effect requires a system with internal magnetism or external magnetic field and exhibits, say, circular dichroism for reflection measurements. Natural optical activity can have ...
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Voltage drop in function of electric field and current distribution
For a wire, the voltage drop $\Delta V$ over a length $l$ of the wire is given by $\Delta V = \int\limits_l \mathbf{E}\cdot d\mathbf{l}$ with $\mathbf{E}$ the electric field. How to calculate this ...
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Difference Between Plasma Potential and Floating Potential in a Plasma
I'm learning about Langmuir probes and I'm confused about the difference between the plasma potential $V_p$ and the floating potential $V_f$.
From my understanding, when a plasma is in contact with a ...
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What is degeneracy pressure?
What is "degeneracy pressure"?
I know there are 4 fundamental forces- EM, gravity, weak and strong. But then degeneracy comes along ubiquitously in everything right from neutron star to the ...
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Can photons interact with one another? [duplicate]
Photons can interact with matter, particles, nuclei, etc.
But can they interact with one another?
By interaction I mean any kind of physical interaction: Momentum/Energy transfer, electromagnetic ...
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Force on current carrying loop due to non-uniform magnetic field
I was been taught that when there is a non-uniform magnetic field then the Force on a current carrying loop with Magnetic Moment M is F = M(dB/dx) where B is magnetic field.
I can't get hold of this ...
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Does the electric field ($E$ caused by induction) of a moving conductor in a magnetic field drop when connected to a curcuit?
We know that when a conductor moves in a homogenous magnetic field that is perpendicular to itself due to the amount of electric charge gathered on one end of the conductor( as a result of the lorentz ...
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Derivation of the formula of the magnetic pressure exerted on a steady surface of current
How might one derive the magnetic pressure , $ P_B = \dfrac{B^2}{2\mu_0}$ exerted on a surface of current of density $K$?
(I have observed it to be analogous to the formula of the electrostatic ...
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Quick question regarding Larmor precession and bar magnets
I was just reading a bit about magnetic dipole moments, Larmor precession, angular momentum etc., but there was one little thing that was bothering me. As far as I know, any angular momentum will ...
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Why is the length of a Faraday cage's lattice relevant to what wavelengths it blocks?
I believe the title is self-explanatory. I see a similar reasoning pop up often in other areas where EM radiation is being manipulated, e.g. lasers, radars, radio telescopes and so on.
The wavelength ...
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Deriving dispersion relation of hyperbolic material
I am trying to derive the following form of the dispersion relation for hyperbolic material:
From the literature, this dispersion relation is achieved by setting the determinant of the below matrix ...
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Why do ferromagnetic materials have high magnetic permeability?
What is peculiar about the structure of ferromagnetic materials which gives them their high magnetic permeability?
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In a simple battery + resistor circuit, what form of energy is lost from the electrons upon exiting the resistor?
I will give this question a little context. Firstly, as I understand it, as soon as I "close the switch" on a circuit, electric current pretty quickly establishes a steady state where, at any given ...
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Is the frequency dependence of Joule heating due to the skin effect?
In this question, I'm considering two separate effects:
Joule heating, in which energy in a good conductor is lost as heat due to the dissipation of energy during charge carrier collisions.
The skin ...
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Field induced outside a grounded 2D circle conductor by an exterior point charge. A puzzle, not what you think!
A unit charge is placed outside a grounded conducting unit radius circle at the origin. What is the field outside the circle?
This is not the obvious problem you immediately think it is.
A classic, ...
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Terminal velocity of a bar magnet in a long conducting tube (quantitative)
If a bar magnet is dropped into a copper (conducting) tube, it reaches a terminal velocity. I'm trying to derive this terminal velocity.
We know from Lenz's law that $e=\frac{-d\phi}{dt}$.
I'm facing ...
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What actually happens when light goes into a waveguide?
I have only dealt with a rudimentary theoretical treatment of how light propagates inside a waveguide, such as those available in Griffiths.
One thing bugging me is that I still do not know how ...
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Flux change through a loop
I'm having difficulties understanding this thing. It would be lovable if someone could show me its derivations and prove it:
In a conducting loop, there is a relationship between the total displaced ...
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Permittivity real and imaginary parts with similar value possible?
Here's the context; I'm studying biological tissues that are supposed to behave like dielectrics. Using the modified cole-cole equation for theoretical predictions:
$$\tilde{\varepsilon}_r (\omega )= \...
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Transformers: How does current in primary coil change?
I was doing a question on transformers and found this really confusing question:
A 100% efficient transformer converts a 240V input voltage to a 12V
output voltage. The output power of the ...
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Derivation of covariant derivative
I'm currently doing Introductory QFT and was confused about the origin of the additional terms in the covariant derivate. My understanding is as follows:
If we begin with the Dirac Lagrangian ...
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Why electric field increase near the cable connected in AC 220V socket even current is zero?
If I put low frequency electric field meter near the connected cable in AC 220V socket, he show 1200 V/m even if device is turn OFF(zero current), if disconnect cable from socket, field drop to 8 V/m.
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Assessing Error Step Size in Continuous Charge Distributions
For obtaining the electric field for bodies at the macroscopic scale, the discontinuities in the charge distributions are ignored. A continuous function for the charge distribution is considered.
But ...
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Magnetic field for a cylindrical shell in which current flows
If we have a cylindrical shell along the z-axis, with current density $\vec j= j_0 \vec e_z$ and small radius $R_i$ and big radius $R_a$. I tried to find the magnetic field inside by using Ampere's ...
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Force acting on an infinite wire with current inside a magnetic medium
I've recently stumbled on an electromagnetics problem that I don't quite understand.
There is an infinite wire carrying current I that is placed inside a medium with magnetic permittivity μ1. At a ...
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Displacement current and magnetic field in capacitor with dielectric
I have a capacitor with round plates of radius $r_{2}$ kept at a distance $d$, with a voltage $V\left(t\right) = V_{0} \cos \left(\omega t\right).$ Inside, there is cylindrical material with a certain ...
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Coulomb Gauge misunderstanding
If we have $\vec A(\vec r,t)$ and $\phi (\vec r,t)$ and we make the following gauge transformations:
$$\vec A(\vec r,t)'= \vec A(\vec r,t) + \nabla f(\vec r,t)$$
$$\phi(\vec r,t)'=\phi(\vec r,t) - \...
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