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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Does charge carrier concentration vary with magnetic field (due to Hall effect)?
I'm writing up an experiment on the use of the Hall effect to determine charge carrier concentration for n-doped Germanium. Which initially led me to believe that the concentration is a constant for a ...
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No EMF generated on a loop lying outside changing $\vec B$ (but $\vec E ≠ 0$)
If we establish a changing magnetic field in a region of space, circular electric field lines are induced. This electric field extends even after we exit the region of the magnetic field. If a closed ...
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Is it possible for both electric and magnetic fields to have longitudinal component in a rectangular waveguide?
I know a rectangular waveguide cannot support TEM waves, but supports TE and TM waves. In the TE mode, $E_z=0$ and in the TM mode, $H_z=0$ (where propagation direction is along the $z$-axis). I want ...
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Volume distribution of charge in a wire in a DC circuit
According to this and several other articles some amount of charge in a DC circuit distributes itself on the surface of the conductor, making the electric field inside parallel to the said surface.
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Confusion regarding phase
As far as I know about phase if the phase difference between two waves is positive, the former is leading..and the latter is lagging. Then why has D J Grifith stated this?
If the phase of the magnetic ...
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Explanation of crystal formation in a Fitzroy's storm glass with the change in weather conditions
I was recently reading about Admiral Robert FitzRoy's storm glass and how it was used to predict the weather conditions based on the formation of camphor crystals in a sealed glass tube containing ...
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Magnetic force acting on a current carrying wire
I am a high school student and I would like to know why in a magnetic field the Force, $F$, is equal to $BIL\sin(\theta)$, where $\theta$ represents the angle between the magnetic field and the ...
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I don't understand Green's derivation of the Laplace/Poisson equation inside an electrically charged body
I am currently reading George Green's "An Essay on the Application of Mathematical Analysis to the Theories of Electricity and Magnetism"Green's essay to gain some insight into the original ...
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Magnetic field of coaxial cylindrical capacitor
I have a coaxial cylindrical capacitor as shown, with inner radius a and outer radius b.
The potential difference across both cylinders is V. I need the magnetic field everywhere when the inner ...
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Current loop and electromagnetic energy
Take a fixed circular loop of wire in a uniform magnetic field. As far as I can tell, the work we have to do to accelerate the electrons in the wire so a particular current is attained is independent ...
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The puzzling interaction between an anapole moment and external fields
Consider an electrical current distribution with only an [anapole, or toroidal moment] but no electrical or magnetic multipole moments, like this current on a torus:
Its magnetic field is completely ...
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When refrence frame has the same velocity of electron the we observe that electron seems like satatic. Then why it produces megnetic field. And why it [closed]
When refrence frame has the same velocity of electron the we observe that electron seems like satatic. Then why it produces megnetic field.
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Larmor Frequency for Spin Transition
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/larmor.html
Consider the process of Larmor precession of the magnetic moment associated with the spin angular momentum of an electron inside a ...
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Why is potential directly proportional to charge?
In my textbook, it’s written that conductors' charge is directly proportional to voltage and they used this idea to develop the concept of capacitance. How can you prove this for any conductor?
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Why would the peak strength of the magnetic field of an AC-electromagnet be higher than the peak field strength of a DC-electromagnet?
Elsewhere on Stack Exchange several people have said that the average, mean or RMS value of the magnetic field of an AC-electromagnet would be about the same, or slightly lower than, a DC one. But, ...
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Why don't static magnets attract copper wires? [duplicate]
I have a few simple magnets, like 1x2 cm (probably neodymium) magnets and similar smaller circular ones (similar to fringe magnets). They attract a (probably zinc or iron) wire: the wire is ~dark-grey,...
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Moving charge to define magnetic field
Why charged particle has to be in motion to define magnetic field?
Will magnetic force exert any force on a static charge? (as in the static test charge in electric field)
A line from my book reads-
"...
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The absorption of infrared light for regular materials, like fabric wallets backpacks and clothes
I work as a brand partner for a company that produces a patch which strengthens the production of stemcells in the body.
The patches are activated with the help of the bodys own infrared radiation.
I ...
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Electric field under gravity
For a spherically symmetric mass m of radius r and charge q, how does the electric field vary with distance d from the center where d > r.
Does it still vary as $\dfrac{1}{r^2}$ or is there a ...
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Lienard-Wiechert Potentials Issue
I have had some difficutlies in trying to obtain the Lienard-Wiechert potentials of a moving "point charge" and would greatly appreciate any help in this matter. I will adopt the definition ...
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How do I find magnetic force between two particles? [duplicate]
First, for a charge $q_1$ with position $\vec{s}_1$ and velocity $\vec{v}_1$, the magnetic field caused by the particle at position $\vec{s}_2$, the equation I've found is
$$\vec{B} = \frac{\mu_0}{4\...
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Is there a (semiclassical) electric field operator?
So I come from a chemistry background, where the electronic structure of atoms and molecules is central. For practical purposes, we usually work with a charge density operator
$$ \hat{\rho}(r) = q \...
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Is the charge density value in the electromagnetic wave equation necessarily equal to zero?
The transmission space of electromagnetic wave is divided into source free and source region. In the case of source region, the current density is not equal to zero because the electromagnetic wave ...
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Why do we need an objective lens in a scanning electron microscope?
I've been studying scanning electron microscopes quite a bit but can't seem to get my head around why we need objective lenses.
On paper I don't see a reason, if we would want to focus the electron ...
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Can an oscillatory field produced by a time-dependent charge distribution fall off faster than $1/r$?
An electric charge has a field that decays at large distances like $1/r^2$. A charge distribution with total charge zero, but with a nonvanishing dipole moment, has a field that decays at large ...
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Biot-Savart Law
Today we started learning about Biot-Savart law. While deriving the formula, our professor listed out a bunch of relations, which have been experimentally determined,
->dB is directly proportional to ...
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Would it be possible to use Diamagnetic force working along with gravity to make a sort of two-way stream?
I was wondering if it would be possible for someone to generate some sort of two-way stream by positioning a strong NdFeB magnet below an upward pointing tube containing something like a Bismuth or ...
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Location of high and low potential points in motional emf
Okay so in the above image the semi circular loop is rotated and a sector of it is introduced into the magnetic field.
Questions:
I know the magnetic field is constant so no non conservative ...
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Growth of Current in an Inductor Connected Across a Battery [duplicate]
When baterry is connected across inductor with no resistance in circuit, won't the current flowing through it be zero, as inductor back emf will counteract the effect of potential difference due to ...
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Behavior of the Electric- and Magnetic-field under time reversal and parity
The behavior of the electric- $\mathbf{E}$ and the magnetic-field $\mathbf{B}$ und time reversal and parity can be calculated in different ways.
My first solution is to study the transformation ...
