# Questions tagged [electromagnetism]

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.

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### Is there an electromagnetic analogue of thermoacoustics?

I've just learned about thermoacoustic heatpumps. My understanding is that a standing acoustic wave in a tube of gas produces areas of higher and lower average pressure which results in a gradient of ...
1 vote
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### Can two waves have the same amplitude but different frequencies? [closed]

If the question above is true, how is that possible?
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### Why armature is being rotated in DC generator?

I am wondering about why armatures are being rotated instead of being static? The magnetic flux will still cut the armature windings and because of this induced current will be generated. So, why it ...
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### How much can we push the plates of capacitor?

I am currently a highschooler and came across this question in physics A capacitor of plate area $A$ and separation $d$ is connected to battery of emf $V$ and is charged to steady state. Now the ...
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### Explain this para on electric field? [closed]

Suppose we consider the force between two distant charges $q_1,q_2$ in accelerated motion. Now the greatest speed with which a signal or information can go from one point to another is $c$, the speed ...
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### Conservation of a specific type of charge

The Law of Conservation of Charge states that 'the total charge in an isolated system is conserved.' Can we say that total negative and positive charges (individually) in an isolated system is ...
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### Mass Spectrometer [closed]

Say, we have a mass spectrometer and we want to determine the mass ratio of Hydrogen and Deuterium. Suppose the ions are positively charged and $q=1.6 \times 10^{-19}C$. The magnetic field can be set ...
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### Maximum voltage induced in a coil due to an ac current [closed]

Problem Given a coil of cross-sectional area of $A=0.1 \, \text{m}^2$ in which there is a magnetic field of $10 \, \text{T}$ when there is a current of $I=100 \, \text{A}$ flowing through the wire. ...
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### Ampere's law on a finite wire [duplicate]

Consider the circular Amperian loop of radius $r$ in this case. The wire carries a current $I$. Integrating using biot-Savart law gives the field as: \begin{align}B=\frac{\mu_0}{2\pi r}\frac{L}{\sqrt{...
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### Modeling ferromagnetic materials in a primitive python FEA

I am working on a primitive 2D DIY magnetic "FEA" solver for a class project. It's really just a big NumPy array where each element in the array can be one of the following: Air Current ...
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### How do we get from LHP to RCP on the poincare sphere?

A paper that I was reading wanted to transform the jones matrix of linearly horizontal polarization(LHP) to right circular polarization(RCP). The paper states: Consider... $J_{LHP}\to J_{RCP}$... In ...
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### Can the following system work as a perpetual motion machine? [duplicate]

A friend of mine came with this idea ! In the photo ,,we have an external magnet ,and as can be seen in picture ,it shuold interact with the upper magnets( that are similar in design to a padestal fan ...
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### The positive and negative terminal of a coil when the flux through it changes [duplicate]

I want to know what will be the positive terminal and the negative terminal of a coil,when the flux is changing through the coil. I know about the direction of the induced current, but wondering what ...
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### How to identify north pole of a magnet using only a battery, and a copper wire? [closed]

I have a magnet, a copper wire, and a battery. I need to find the north pole, and the south pole of a magnet using only these items. (not a compass). Here's my attempt: create a circuit, battery is ...
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### What is the correct definition of EMF in a circuit?

The EMF $\mathcal{E}$ in a closed circuit $C$ is defined as the closed line integral of the electric field ${\vec E}$ around the loop: $$\mathcal{E}=\oint_C{\vec E}\cdot d{\vec\ell}.$$ But in Section ...
1 vote
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### A doubt about the topic of motional emf from Griffiths

Consider a closed rectangular loop of wire, which is moved to the right with a velocity ${\vec v}$ w.r.t a magnet that provides a static, uniform magnetic field $\vec B=-B\hat{z}$ over a region as ...