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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How does energy travel in the system in a conducted RF immunity test,?

I have a question regarding some conducted RF immunity (IEC 61000-4-6) tests. We inject noise starting at 150kHz until 80MHz. The signal injected is AM at 80%. The level is 20Vrms. Here is the setup ...
Dimitar Zhekov's user avatar
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1 answer
94 views

What is the utility of inductors in circuits? [closed]

I was wondering what all the possible purposes of inductors in electrical circuits are. Inductors, as I understand, are wires wrapped in a helical pattern around some sort of solid material or simply ...
Runsva's user avatar
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How can I calculate the coupling coefficient between two coils?

I have two planar, circular coils of different number of turns, inductances, and radius, stacked on top of each other. How can I calculate their coupling coefficient (k) based on their properties and ...
Theodor's user avatar
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-1 votes
1 answer
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Charges in receiving antenna and polarization if alternating current is changed to stay high

A dipole antenna receiver placed in parallel to a dipole antenna transmitter will have a current induced in the opposite direction to the current in the transmitter. This causes charges (electrons and ...
BipedalJoe's user avatar
4 votes
3 answers
1k views

Why is it not standard practice to integrate the output of an antenna?

This is a follow up question from my question answered here: Why does a loop antenna not measure the differential magnetic field? Essentially I just found out today that we are actually measuring the ...
Christian's user avatar
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0 answers
37 views

Advancing PCB Design Knowledge: Seeking Resources for EMC, Analog Signals, RF and More

I'm designing 4 layer, 2 sided pcbs with MCU, radio module, digital sensors (i2c, UART..) and analog ones (4-20 mA, 0-10V). All on an average budget of 50 uW. Everything is quite slow here, 115200 ...
Alexander Ohm's user avatar
1 vote
2 answers
123 views

How does electricity flow if circuit is not complete? [closed]

https://youtu.be/oI_X2cMHNe0 What is he saying at 13:20? How can bulb glow if the circuit is not complete?
Shubham Singh's user avatar
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0 answers
39 views

How to create RF source in CST Studio

I have designed a microstrip patch antenna in CST studio and I want to test its efficiency for energy harvesting. Having followed some youtube videos, I understand creating a waveguide port across the ...
KimchiKiller's user avatar
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0 answers
267 views

Transformer Phasor Diagram And Circuit Diagram

I have been reading the construction of a practical transformer and facing difficulty in understanding the phasor diagram of it. When we connect \$V_1\$ supply to the primary side, say \$V_1 = sin(wt)\...
Preet's user avatar
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1 answer
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UPML and tensor multiplication?

I am studying uniaxial perfectly matched layers. In order to absorb outgoing waves we introduce a tensor S (I have anderstood how it is calculated) \begin{bmatrix} \frac{s_y s_z}{s_x} & 0 &...
MementoMori's user avatar
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72 views

Help with circuit for school

I am doing a project for school with two friends. We are going to make a DIY metal detector. We are using a source as our circuit. Can someone help us describe what is happening in the circuit?
Mattiz Ketels's user avatar
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Is this Molex flexible antennas feeding method consider insert or probe feed? what is the most accurate way to simulate it in HFSS?

I want to do some data augmentation to the radiation pattern of an off-the-shelf flexible antenna (in terms of bending, material, size...etc). To get started I tried my best to recreate the trace ...
Xingda Chen's user avatar
0 votes
2 answers
49 views

Understanding voltage in simple electromagnet and DC motors

I made a simple electromagnet with enameled copper wire wrapped many times around a metal allen wrench. I attached the electromagnet to my PSU and it works great, but I do not understand the voltage ...
vm1988's user avatar
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1 answer
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Fundamental Question - how does magnetic permeability work for weak signals?

This is basically a physics question. If a sophisticated answer is needed, please go for it. The standard explanation of magnetic permeability is something like this: In a ferromagnetic material, ...
Colin Marcus's user avatar
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Metal detector discrimination problem

I was experimenting with discriminating metal detector I'm using TX coil about 28cm diameter, and 0.9mH with 470nF capacitor- pushing about 5Vpp sin wave from a signal generator The RX coil also about ...
Ron Vaisman's user avatar
5 votes
3 answers
1k views

Building an MRI safe video camera (e.g. webcam)

I would like to use a small camera inside an MRI. The eye-tracking cameras that are commercially available are both too expensive and also not suitable for my purposes. How would one go about making a ...
socialresearcher's user avatar
0 votes
1 answer
80 views

How do I create an AC electromagnet for a particular type of field generator?

I’m trying to generate a special sort of field in a spherical spinning iron core using two orthogonally oriented coils. One single-layer coil of 18 AWG magnet wire is wrapped directly onto most of the ...
magnetwhisperer's user avatar
1 vote
0 answers
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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{...
Jes's user avatar
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1 vote
1 answer
710 views

Parallel magnetic circuit with 2 air gaps

I have the following ferromagnetic core. N = 300 core thickness = 5 cm relative permeability = 2000 the air gap's efective area rises 5%. 1 A going through the coil I need to know the flux going ...
Aleat's user avatar
  • 177
0 votes
2 answers
152 views

Voltage generated by individual coils goes down the larger the number of coils

I'm trying to make my own alternator & study the physics behind it. So I have a circle of magnets rotating over 4 coils, forming a square (90 degrees each). When I remove 3 coils from the square ...
Charles-Ugo Brouillard's user avatar
1 vote
2 answers
50 views

EMF Sensors - Tri-axial Inductors vs Tri-axial Magnetometers

I took apart a bunch of EMF sensors (such as this one) and found that almost all of them instead of having a magnetometer inside, have usually three inductors. In the case I just shared, it has 3 33mH ...
Tom Hayden's user avatar
0 votes
2 answers
120 views

Equation relating alternating magnetic field strength to induced voltage in search coil

I have a search coil (loop area A, N turns) placed normal to an alternating magnetic field with equation B(t)=Bp.sin(2.pi.f.t), B=field strength at time t, Bp=peak field strength, f=frequency, t=time. ...
user201341's user avatar
2 votes
3 answers
714 views

Moving magnet frequency over a coil

It's my understanding that : Changing magnetic field over a coil induce current in the coil itself. Current running through a coil makes it magnetic. (To put it simply) Can these 2 rules affect ...
Charles-Ugo Brouillard's user avatar
4 votes
3 answers
949 views

Understanding the flux linkage in transformers

I am having difficulty understanding the concept of flux linkage in transformers, particularly how the secondary winding receives its flux when all the flux is said to be confined to the iron core. I ...
Adhithya S's user avatar
1 vote
2 answers
113 views

Analysing the behaviour of inductor in the circuit

Suppose we have an L circuit with DC power supply of emf \$\mathscr{E}\$ simulate this circuit – Schematic created using CircuitLab By KVL, \$\mathscr{E}=L\frac{dI}{dt}\$. This suggests that \$\...
Iti's user avatar
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1 answer
96 views

What's the best solution for creating a magnetic field around a small cylinder?

I'm a beginning electronics hobbyist so forgive the naive question. I'd like to have a small cylinder (1cm radius, 3-4cm length) where I could control a magnetic field around the cylinder with voltage....
Lucian Thorr's user avatar
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0 answers
62 views

Making an automated chessboard [duplicate]

I want to create an automated chessboard. At the moment, I'm making the project and deciding what technology to use to detect which piece is at what position and how to move them. I'm not so skilled ...
Mukund's user avatar
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0 votes
1 answer
54 views

In what direction does skin effect take place?

I'm working with some problems with coaxial cylinders and the currents driven in those when considering high frequencies. In such cases, the skin depth has to be taken into consideration. One thing I ...
Tanamas's user avatar
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1 vote
1 answer
39 views

Why do we still need to calculate the equivalent exciting current \$I_{eq}\$ when we have the exciting current \$I_F\$ already?

Here is the compound DC machine schematic: The equivalent exciting current is \$I_{eq}=I_F+\frac{N_{SE}}{N_{SH}}I_A-\frac{F_{AR}}{N_{SH}}\$ \$F_{AR}\$: the equivalent magnetomotive force of armature-...
user16266657's user avatar
1 vote
1 answer
35 views

Angular speed and voltage-intensity

I have a square frame with 200 windings rotating in a magnetic field B=0.2T. If I increase the angular speed of rotation of the frame will only the voltage increase? will the electric current also ...
liontass's user avatar
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2 answers
160 views

Why is only the electric field considered in the calculation of the total radiated power of an infinitesimal dipole above ground?

I don't understand how the average energy density and total radiated power of an infinitesimal dipole above a conductive surface is being calculated and why the magnetic field is not being considered ...
Shakiba HS's user avatar
1 vote
1 answer
105 views

Can a solenoid be made of copper strips?

Could a coil of copper strips instead of copper wires be used as a solenoid? Are there any real world examples of making solenoids out of strips of copper?
David johns's user avatar
2 votes
0 answers
99 views

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 ...
Danko Dnevic's user avatar
0 votes
0 answers
60 views

Equivalent circuit of spiral resonator metamaterial

I require equivalent circuit for two sided square spiral resonator for metamaterials. I have found the equivalent circuit for one side, according to this paper: https://www.researchgate.net/...
FreddyBoat's user avatar
0 votes
0 answers
123 views

AC - impedance for a coaxial cable

Problem I want to calculate the AC impedance for a coaxial cable. A rough image is presented below: Because we have an AC current, suppose that the skin depth, which we can define as \$\delta\$ is ...
Tanamas's user avatar
  • 313
2 votes
2 answers
574 views

Why must an antenna be connected to ground?

My physics textbook states that connecting one plate of a capacitor to ground and replacing the other end with wire makes an antenna. So is an antenna really a capacitor? Does one end really need to ...
Kefas's user avatar
  • 89
0 votes
3 answers
197 views

Torque on generator due to reactive power

Since reactive power goes back and forth from load to generator, so when reactive power goes from load to generator this should manifest as torque that's exerted on the rotor right? (like that of a ...
diode's user avatar
  • 21
1 vote
3 answers
731 views

How does this toaster fix work?

Let's pretend your toaster need a little fix. Pulling the lever down, it does not stay low and immediately jump to its rest position. Apart from this, manually keeping the lever down, toasts your ...
InfiniteLooper's user avatar
0 votes
2 answers
130 views

How can energy be stored in a magnetic field?

A magnetic field can be thought of a vector field of force on electrons. Basically this can be thought of a some area that attracts or repels electrons. It is said that inductors are able to "...
Leftover Salad's user avatar
10 votes
2 answers
717 views

Parallel decoupling capacitors: Is inductance reduced?

Background In general, when placing decoupling capacitors in parallel, their capacitances add and their compound ESR is reduced (like for parallel resistors). But I am a bit uncertain if/how this ...
tobalt's user avatar
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0 votes
2 answers
54 views

Is power dissipation constant for a given mass of copper generating a given magnetic field?

What I mean, is that for a given field and a given mass of copper coil, power dissipation is independent of the form of that copper, whether thick wires or thin. Is it true?
Dirk Bruere's user avatar
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2 votes
3 answers
362 views

Does infinite magnetic permeability (e.g. for an ideal transformer) violate conservation of energy?

The ideal transformer is supposed to have infinite magnetic permeability. Creating infinite magnetic field lines from a finite applied field sounds like... a violation of conservation of energy or ...
artist_and_not_EE_by_training's user avatar
2 votes
0 answers
146 views

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 ...
user avatar
0 votes
2 answers
86 views

calculating magnetic field strength (H) of half wound solenoid or toroid

at school, I learned that the magnetic field strength(H) is defined by the Number of turns*current/Length. is the length in the formula the length of the coil or the core? so if an iron rod is 10cm ...
asker's user avatar
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0 answers
15 views

Query on labeling directions for electric force

On the second part of the problem, is my assumption correct? Do I even need to put the sign? or is the magnitude alone suffices as the answer?
Wolfram's user avatar
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0 answers
58 views

Electric field intensity problem

I have done two solutions regarding this problem. One with the unit direction and one with no direction (magnitude only.) All of these solutions are an exact copy of how my professor answered a ...
Wolfram's user avatar
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0 votes
0 answers
50 views

Calculate potential between two rods

Suppose we got four thin, long and parallell conductors with charges shown in the image below. Each conductor has a radius \$ r\$ and length \$ l\$ . Our problem is to find the potential between the ...
Tanamas's user avatar
  • 313
0 votes
0 answers
77 views

Voltage seen at load which has open circuit in parallel

If I send a sinusoidal signal down a transmission line, say with a source and line impedance of 50 ohms. Then if I have a 50 ohm load, in theory, there are absolutely no reflections. If however, I ...
Electronics Wizzter's user avatar
1 vote
1 answer
295 views

How does the electric field inside a conductor remain zero?

I'm learning about current in conductors, and came across the statement that "The electric field inside a perfect conductor is zero", this is frequently explained used Gauss´s Law by saying ...
Seidenki's user avatar
-3 votes
2 answers
119 views

How do we maximize core and winding losses in an electromagnet (and calculate them) for variable DC input?

Bigger Picture: Imagine a magnet approaching the solenoid with some initial constant velocity on \$v_0\$ on x axis. The approaching magnet will induce an EMF and induced current in solenoid. We want ...
student0's user avatar

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