Questions tagged [electromagnetism]
The kind of magic without which all of this wouldn't be possible. This tag should be used for questions about the **physics** of the fields that charged particles create and how these fields interact. It should not be used for all questions involving electromagnetism; that would be everything on the site.
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questions with no upvoted or accepted answers
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What role does permanent magnet strength play in BLDC/PMSM performance?
It seems to me like stronger permanent magnets are preferred by motor designers, but my current understanding of what role they play in performance is fuzzy at best. I would assume that stronger ...
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Building an electromagnet to work over an air gap
I am currently working on a project where I am building an electromagnet that works over an air gap. Specifically a gap of about 0.3 inches. The electromagnet type was selected because I need to be ...
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Is there any way to wind this 4 pole motor to behave as 2 or 8 poles properly?
I got an induction motor in a junkyard, a WEG motor made for an Electrolux washing machine.
It is a single-phase 1/2 hp 4 pole motor. It runs in 127 V and has a 40 uf capacitor feeding the auxiliary ...
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What's the circuit diagram symbol for a variable reluctance sensor transducer?
I know I've seen the symbol before, it's something like a circle with an open triangle facing in the direction of current flow with a line through the middle. I'm specifically thinking of the ...
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Spiral hoar frost and spiral device around telephone or electric landlines
I live in Germany.
When I travel by train, sometimes there are cables that run from pole to pole parallel to the train track.
From the lack of insulation between wire and pole, I guess these are ...
user205148
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How can a wire be influenced by a electromagnetic field?
I have a problem in one of my project. Here are some details:
A train is moving on tracks. To know its location, some beacons (transmitters) were placed at different locations in between the two ...
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Analytical solution for the characteristic impedance along vertical wire over PEC ground plane (at given point h)?
For the purpose of TL transformer simulation I need a solution for the characteristic impedance of vertical wire, with radius a, at the infinitesimally short segment - not point, at the height h above ...
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ESD problem and how to solve
We have a problem with contact discharge of 3kV on a housing part. The PCB with the PHY are installed in an aluminum lower part with plastic upper part (dimensions approx. 80x80x80mm). The contact ...
user220456
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A question on radar cross section of rain by using radar reflectivity factor
The question is one of the past exam papers of the RADAR 1 course given in TUDelft, unfortunately, solutions are not provided to the past paper yet.
The question:
What will be the radar cross-section ...
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Does acceleration come from a change in current?
I have a current connected to a wire and let's say when we measure the current at a particular time it reads differently than it does after some time.
Does this imply the current is AC?
I'm asking ...
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De-embedding ceramic filters
I want to design a diplexer using two ceramic filters.
S2P files of the filters are not provided. Therefore, I designed a PCB which can be shown below to obtain their S2P parameters.
In the first ...
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Fourier transform of the electrical conductivity function
In this pdf https://studylib.net/doc/18704299/chapter-1 the author writes that the Fourier transform of the current density is:
$$
\Delta j_{i}(\mathbf{k}, \omega) \equiv \frac{1}{(2 \pi)^{2}} \iiiint ...
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Contour (curve) selection in the Ampere's circuital law
I need help understanding Ampere's circuital law. Consider a square shaped iron core with an N turn coil on one side. Let each side of the core has the length a an has equal cross-section. The ...
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How to apply Ampere's law with the integration path crossing a permanent magnet?
I read several books on permanent magnet synchronous machines (PMSM), and they tend to describe the relationship between H and B as \$B_{mag}=\mu_0\mu_{r,mag}H_{mag}+B_{rem}\$.
Then when they apply ...
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Problem with switching solenoid valve by relay
I've been trying to drive a 12volt solenoidal valve with a 5volt relay .Relay is working perfectly for driving normal loads(light bulbs).But it is not driving my 12volt solenoidal valve.
I've already ...
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Magnetic field in the center of a coil
I have a closed core with a coil attached to it and metal inside the core. The N is 100, I is 100mA and l = 300mm. I have computed the magnetic field B = (μ0 * μr * N * I) / l. But I have also given ...
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In an induction cooktop, what happens to the coils resistance when there is no pot? Does it vary between pots? How does the appliance respond?
An induction cooktop (or an induction rice cooker) uses a copper coil with a high-frequency alternating current going though. The magnetic flux heats any iron-alloy pot placed above.
But what ...
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What would be the effects of a -1000 nanotesla geomagnetic storm be on modern electronics?
After reading the Wikipedia article on geomagnetic storms, I'm curious about what the effects of a -1000-nanotesla-minimum geomagnetic storm would be on modern military and consumer electronics, as ...
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What are the consequences of not having a magnetic field in the atmosphere on electronics?
Electronics super-noob here! (I did EE in school but have managed to forget practically everything since, to an alarming degree!).
I'm wondering how the field of electrical engineering and electronics ...
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Reverse electrowetting on dieletric using air bubble displacement for electricity generation
I read this research paper and it uses bubbles to change the electrolyte and electrode interface, thus causing a change in capacitance as the bubble forms and exits the electrolyte.
For reference: ...
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Are transistors on MMICs considered lumped elements?
Are transistors, in practice, always small enough to be considered lumped elements in Monolithic Microwave Integrated Circuits (MMICs)? Similarly for discrete transistors used in hybrid microwave ...
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Coil winding direction in a shaded-pole motor (4-pole)
I have rewound a shaded-pole motor (4-pole).
It's wound around the stator in a clockwise motion and around each coil in a counter clockwise motion.
Is the winding being incorrect the reason why the ...
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How could you make a polarity-switched electromagnet at home?
For context, I have lots of electrical parts and I am looking into ways to make a small polarity-switched electromagnet out of the parts I have. I can Information on the parts I have if needed. If ...
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How to simulate a Large Structure at low frequency in CST Microwave Studio?
In CST Microwave Studio, I attempted to simulate a large (215x30cm) loop structure at 1kHz. However, CST gives a warning of 'too large' mesh size. The mesh size increases up to 6 Billion, however, if ...
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Transformer Design and Ripple Formula
When I was researching flyback inductor I saw a formula which is showing the effective transformer core volume with related the ripple factor. r = 2Iac/Idc = ΔI/Idc
Where does this formula come from?
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Formula relating attenuation and loss tangent in EM wave propagation?
in this previously answered question, a relation is established between the attenuation and loss tangent in EM waves. The formula given is the following:
$$ \alpha = \frac{\omega}{c} \cdot \sqrt{\frac{...
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Winding coils in an AC generator
Assume a coil arrangement in an AC generator like the one seen below:
Given that the magnet has one pole on each side (2 poles in total in the magnet), how must the surrounding coils be wound? In ...
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Dowell 1-D Eddy Current Model
About this paper, I have a question; please see the yellow part.
I don't understand why the current density distribution in
the conductor is only related to the y-coordinate.
Can someone tell me in a ...
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How powerful would be a Bitter configuration electromagnet made of aluminium foil?
The specs:
The electromagnet has 7,2 cm of height, 1 cm of radius.
A hole with 2,5 mm of radius in the middle.
An aluminium foil has 0,024 mm of height so I assumed the insulator layer has the same ...
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Why is physical optics an approximate technique?
Consider the problem of known electromagnetic source in free space near a perfect electric conductor (PEC) object. Finding the total electromagnetic field in this situation can be done through solving ...
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How can I set up a reed switch/magnets on an electronic chess board to consistently detect pieces?
My goal is to build a chess board that can detect the movement of pieces on it. My current approach that I'm testing is to have a reed switch underneath each square and magnets attached to the bottom ...
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How to create an equivalent circuit model for the excitation in HFSS EM field calculation?
I am new to circuit simulation, and now got stuck in the problem of modeling the excitation when transforming a electromagnetic field calculation problem into a circuit calculation. I would appreciate ...
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At which point do we take the value of impedance to tune an antenna?
I am a beginner in antenna design and tuning.
I want my antenna to have a resonant frequency of 2.45GHz for low-energy Bluetooth communication, and I want to know what to consider for the matching ...
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RFI noise impact on ADC
I am trying to debug the issue where RFI noise is increasing the ADC's analog input values when a Walkie-Talkie is switched on (transmitter mode, 470MHz) nearby.
What could be the quick tips to ...
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Modelling a single trace PCB?
I am trying to model a PCB trace as a R, L, C circuit.
Assumption: My PCB has a a single trace running through it. Just giving input from one side and taking output from other. There is not even a GND ...
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Multiple questions about magnetic levitation including modelling and how to achieve it
I have several questions regarding magnetic levitation. If I have missed something in one of these questions then please do let me know.
I am working on a magnetic levitation project using an Arduino ...
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What are the components I would need for an electromagnet with the given specifications?
I need to make an electromagnet that exerts at least 5 times its own weight on a ferromagnetic material kept 0.03 m away.
I know that:
F = [(number of turns × current)2 × magnetic constant(4 × pi × 10-...
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What generates the torque to rotate this micromirror around the _vertical_ axis?
I can see current in the coil could interact with a magnetic field could cause the coil to rotate around the horizontal axis (flexures 310 and 312), but what forces are making the inner micromirror ...
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Transmission Line Power Flow
Background:
So, I recently watched Veritasium's video, "The Big Misconception About Electricity" and EEVblog's response to it.
Here is the circuit in question:
I think understand why the ...
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Direction of magnetic flux of mutual inductance where coupling coefficient is almost 1
I've drawn the below diagram of the circuit.
We will handle the system as the switch is closed .
The coupling coefficient of the system is almost 1
I assumed \$~ L_{1} ,L_{2},M ~\$ are all positive ...
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(Too?) simple model of a pn junction
I want to build a simple model of a pn junction in order to show high school students how it works. I am not looking for something precise, so I use really simple discretization and I discard units. I ...
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magnetic flux winding
If an electric wire carrying some current is wound on a soft iron core, the magnetic flux increases according to the winding turns.
Does the same hold for winding the core, eg. winding a soft iron ...
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Autotransformer equivalent circuit
I am trying to find an equivalent circuit for autotransformer. But there is no any source about it. I tried to solve something about it. Can anyone have any idea about it?
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How to calculate the pressure and velocity of an ionised gas that is being impelled with magnetic pressure
Calculating the velocity and pressure of an ionised gas based on magnetic pressure and magnetic force.
Questions:
Based on magnetic pressure expressed on an ionised gas, how do I calculate the ...
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Current source and electromagnetic interferance
I have a current source which has to be really precise in order to charge a capacitor and count a certain time (about 100 ms.)
If anybody has seen a component which allows to count a time (without a ...
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0
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Designing an electromagnet
I'm new to magnetics and apologize in advance if any of these questions are too basic. I'm looking to build an electromagnet array to move around an object placed on top of the array. Something ...
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What is the purpose of a superstrate above a printed antenna?
I've seen that there are some planar antennas which are not simply a metal patch above a substrate, but present also a dielectric superstrate.
Some examples of this configurations are:
This planar ...
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How do i find the FNBW of a main lobe using a diagram?
Looking at the graph below, i can see that HPBW of the main lobe is around 45 degrees, but when it comes to identifying the FNBW i have trouble understanding it. Reading various articles online i've ...
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Determining Electric Field on a Charge Plane
Question:
A plane \$x+2y=5\$ carries charge \$\rho_s=6nC/m^2\$. Determine electric field at \$(-1,0,1)\$.
My try:
At first, I calculated gradient
Let, \$\phi=x+2y-5\$
\$\begin{align}\\
\vec\nabla\phi&...
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Loop inside a loop, where is the mutual inductance greatest?
I had a question while working a problem as to where the mutual inductance of a circular loop inside a rectangular loop is greatest.
Is it at the center, because the magnetic field of all four wire ...
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