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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Fields and quantities
I'm a bit confused about the concept of a field defined as a physical quantity. For example on the Field (physics) Wikipedia page a field is defined as a
physical quantity, represented by a number or ...
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Thought experiment: EM fields and coils
Hello Physics Exchange,
I have been thinking a lot lately about EM fields. I thought about something the other day and wanted to check with the experts if my intuition is correct or not. I know this ...
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In Maxwell’s Fluid Analogy, is the Magnetic Field the “Wake”?
Does Maxwell's analogy of incompressible fluids extend so far that the magnetic part of a wave created by a moving electric charge is like the "wake" of a moving body through fluids, only ...
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Problem from Electromagnetic Induction of IE IRODOV
According to Faraday's law, a change in the flux associated with loop generates an EMF in the loop and when we are bringing the loop into the region containing field obviously the flux associated with ...
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How would the field in between two semi-infinite placed next to each other look like?
Suppose two semi-infinite solenoids placed next to each other are separated by a small gap as shown below
If the solenoids are identical to each other, What would you expect the field in between the ...
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Can we explain the perpendecularity of electric and magnetic vectors in the electromagnetic wave in a 'physical and tangeable' sense? [closed]
ive tried my best to understand the physical why behind it with the relativistic contraction from lorenz transformation so here is what i know correct me where am wrong :
The magnetic field arises ...
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What actually is the EMF in a current carrying wire?
My basic idea of what a DC current is that, when a potential difference is applied to the ends of wire it creates a force which propagates through the wire all the way to the other end. It propagates ...
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Does the Fermi surface drift opposite to electrons in an electric field?
I have encountered somewhat of a paradox when it comes to electrons in an electromagnetic field. I hope someone here knows where the problem lies.
Upon minimal coupling of a free classical electron ...
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Maximum Impedance for LCR series circuit
Impedance of an LCR series circuit can be maximum when either Inductive Reactance or Capacitive Reactance is maximum at an instant of time.
Max Capacitive Reactance is at minimum frequency, and max ...
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Is the north pole magnetic field negative charged & south pole magnetic field positive, plus other questions [closed]
Firstly. does the north pole magnetic field have a "majority" of "negative charge", while south pole have a "majority" of "positive" charge ? If so, then there'...
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Units of Poynting vector (or flux of energy) and field intensity
In optics, the Poynting vector of an EM wave is
$$\boldsymbol{\mathcal S}=\frac{c}{4\pi}\,\mathbf E\wedge\mathbf H$$
and if I am not mistaken its units in the SI system should be $\mathrm{W/m^2}$, or ...
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Electromagnetic energy density in dielectric
Poynting's theorem can be interpreted to show that the total electromagnetic energy in a volume from the electric field is
$$\frac{1}{2\epsilon_0} \int_\mathcal{V} E^2 dV$$
However, when using Maxwell'...
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Faraday's paradox
I have studied that Faraday's law of induction and motional emf are two different lines of thinking but are essentially same.
But then, how can Faraday's paradox be explained by Faraday's law of ...
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Are electric fields a physical input of the real world or a mathematical elaboration of Coulomb's law? If it is real what is it?
If the electric field is real, how does it affect the way we see the world? Or does nothing change? Is there a different interpretation between classical and quantum view of the electric field?
I am ...
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How to derive the magnetic field at a distance $x$ (in the same plane) from the centre of a circular loop with current $I$ and radius $R$? [closed]
how to get the expression for magnetic field at any point in a circular loop (plane) with current $I$ and radius $R$, I can't seems to find it anywhere and all I'm getting is the derivation for ...
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Explaining how a magnetic field affects currents in a conductor, in the limit of high conductance
Recently, I gave an answer to this question,
explaining my intuition on how much electric field impinges into
a good conductor under certain conditions, in order to reason about the limit of
perfect ...
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Papers About electromagnetism [duplicate]
What papers by people who developed electromagnetism are worth reading to help understand their original thoughts?
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Flux pinning upon a ultracold vapor of neutral atoms
Suppose I have a mixture of two different atoms A and B, both with an even but different number of electrons. The two are different elements.
Now, suppose I turned both into an ultracold vapor. Atom A ...
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What parameters of a material must i know to deduce its internal electromagnetic field?
In continuum physics, it is assumed that an open region in space $\Omega$ that contains a given substance has the standard topology in $\mathbb{R}^3$, is isotropic and is homogeneous everywhere... But ...
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Magnetic potential energy in a Gauss gun
How does magnetic potential energy have an effect on the velocity on the final ball of the gauss gun (magnetic linear accelerator)?
it is said that the kinetic energy of the last ball (the ball that ...
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What the hell is going on with electricity? [closed]
I am doing an engineering project and I need to understand basic stuff like Voltage, Electricity and Resistance. But I don't understand anything, electricity is much different than let's say special ...
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Physics of microwave oven
I am looking for a definitive discussion of the physics of microwave oven - I mean I would like to see actual evidence in favor of this or that explanation, rather than just popular physics/...
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How come electrons are negatively charged when they can have a spin that can make them appear to be positive or negative when unpaired?
It is commonly denoted that electrons are negative and move opposing to Magnetic field, however doesn't the Stern-Gerlach experiment contradict this as it shows how electron spin can make unpaired ...
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Dispersion Relations in a Cold, Unmagnetized, Collision-less Plasma
Currently I am trying to understand the physics of waves in cold plasmas. So in a cold, collison-less, unmagnetized plasma you can derive two different different dispersion relations: one for ...
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Classical limits of Quantum Electrodynamics?
Quantum Electrodynamics is the theory that studies the interactions between matter and radiation (somewhat).
How would one explain for example the movement of an electron in a constant electric field ...
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Would mechanically moving electrons create a super-strong magnetic field?
According to this Veritasium video, the magnetic field in a wire with a non-zero current is an artifact of special relativity. A moving charge sees a speed difference between the wire and the ...
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Deriving Lagrangian density for electromagnetic field
In considering the (special) relativistic EM field, I understand that assuming a Lagrangian density of the form
$$\mathcal{L} =-\frac{\epsilon_0}{4}F_{\mu\nu}F^{\mu\nu} + \frac{1}{c}j_\mu A^\mu$$
and ...
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Interaction of light and charge leading to uncertainty in position?
To understand hysemberg uncertainty principle first I want to understand the uncertainty in position term . In hysemberg thought experiment he told that the uncertainty in position is due to the ...
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How to transform the volume integral of a curl of the product of a potential with a magnetic field into a surface integral?
Problem 6.5 of Jackson electrodynamics says:
A localized electric charge distribution produces an electrostatic field, $\vec{E} = - \vec{\nabla}\Phi$. Into this field is placed a small localized time-...
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Deriving the Electrostatic boundary conditions
When deriving the electrostatic boundary conditions for any charge distribution (to my knowledge at least), Griffiths in his textbook references this illustration:
So, when considering the boundary ...
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Interpretation of Diffusion Coefficient in Photon Diffusion Equation
The diffusion coefficient in photon diffusion, as explained/defined here: Factor of 3 in Photon Diffusion coefficient
seems counterintuitive because diffusion is inversely proportional to the ...
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How does a wireless charger work if there is no transfer of electrons?
I have read this:
the definition of electrical current is the flow of charge.
Now, it is also possible to transfer energy (and therefore power) through either free space or a conductor by ...
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Wrapping a Voltmeter Around a Solenoid
I just read this really interesting paper by Robert H. Romer and it has me curious: what would happen if you wrapped the positive lead of a voltmeter once around a solenoid with a linearly increasing ...
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Will the potential on surface of a irregular conducting sphere surface be constant?
We know that potential on surface due to a regular conducting sphere is constant. But what will it be when the surface is irregular and charge distribution is non-uniform?
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Why is the Voltage across the coil the difference between the induced emf and the total voltage [closed]
I understand all of this question except for the very end.Its from a test I was looking at from a couple of years ago.
A coil consists of 150 turns of wire and has a total resistance of 200 Ohm.
It is ...
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Non-homogenous Helmholtz equation in 3+1D: Green's function and solution
I've been reading Jackson's Chapter 8.10 and trying to find the Green's function for a non-homogenous Helmholtz equation. The problem is in cylindrical coordinates.
I first made a Fourier transform to ...
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Why can we calculate the electronegativity of an atom? [closed]
learned about electronegativity from my teachers at school, but none of them explained how to calculate or why there are data on the electronegativity of an atom. For example: the electronegativity of ...
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Photon and Observer effect
We cannot determine the position and momentum of a particle simultaneously with certainty . The product of uncertainty of them is greater than or equal to reduce planck's constant . The reason for ...
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Magnetic flux through circular loop
Purcell says
If finite current flows in a filament of zero diameter, the flux threading a loop made of such a filament is infinite! The reason is that the field $B$, in the neighborhood of a ...
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Doubts regarding the statement "Ampere's circuital law does not depend on Biot-Savart Law"
Here Ampere's circuital law is specifically referring to: $\oint{\vec{B} \cdot \vec{dl}}=u_o\cdot I $ , I do not think it's also considering the displacement current, according to the statement.
Since ...
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Metals behaving as dielectrics for certain frequencies
I'm studying the complex refractive index of material media, which is given by:
$$n_c=n+i\kappa$$
where $n$ is the refractive index and $\kappa$ is the absorption index. I interpret this as though $n$ ...
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Application of Faraday’s law of EMI [closed]
I’m a high school student. In this question the magnetic field is confined to a cylindrical region. I’m assuming that the answer will be same if the magnetic field was not confined. Is my assumption ...
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Apparent paradox of current through two parallel plate capacitors in series in an open circuit
This apparent paradox has been wrecking my brain. Suppose we charge up two parallel plate capacitors (with distance $d$ between each pair of plates) independently with different batteries to voltage $...
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Magnetic field of a uniformly moving charge paradox
Suppose we have 2 charges $q_{1}$ and $q_{2}$ in a constant $\vec{r}$ distance from each other.
Now lets calculate force of magnetic field for each of them.
$\overrightarrow{\mathbb{F}_{12}} = \frac{...
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Physical interpretation of a dielectric's absorption curve
A given dielectric will behave as an absorbing medium for some frecuencies (those near one of the material's several resonant frequencies), whilst it will behave as a non-absorbing medium for the rest ...
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Now some say its product of special relativity effects.if so why do we still consider it fundemantle propretie and treat it as a seprated phenoman [closed]
I am at highscool so am not ready to talk in professional manner but from what i understood from lorenz transformation equations is that electric field is just manifested as magnetic field in other ...
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If there's magnetic field around current-carrying wire, why doesn't it always exist?
Motion is relative.
If we say train is moving, it moves with respect to the Earth. If we are inside, it doesn't move from our point of view.
Then, with respect to what object do we say that electrons ...
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If a material is homogeneous in $\varepsilon$, can this material be made of different atoms?
I'm currently trying to derive the microscopic expression for the dielectric constant of a material following my proffessor's notes. However, he admits that, even though he assumes $\varepsilon=...
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Finding net force on third point charge [closed]
Why the teacher wrote F13's direction as (i-j)/2*sqrt 2
Shouldn't it be (i-j)/2
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Why do two magnets facing each other with opposite poles but offset horizontally repel?
When you place two magnets with opposite poles facing eachother vertically they attract. However if you move one magnet horizontally by a distance greater than the magnets diameter they will begin to ...
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