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Questions tagged [electromagnetic]

Electromagnetism, or the electromagnetic force is one of the four fundamental interactions in nature. This force is described by electromagnetic fields, and has innumerable physical instances including the interaction of electrically charged particles and the interaction of uncharged magnetic force fields with electrical conductors.

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Electromagnetics - Capacitance of a two wire transmission line

This is a problem from a book. Two #16 AWG copper conductors (diameter = 1.29mm) are parallel with a separation d between their axes. Determine d such that the capacitance per unit length between ...
Amit M's user avatar
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Energy stored in a capacitor with dielectric

This is a problem from a book. The exact words of the problem are below: A condenser of 1 µF contains titanium oxide (\$TiO_2\$) as a dielecric with \$ε_r\$ = 100. For an applied D-C voltage of 1000 ...
Amit M's user avatar
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1 vote
1 answer
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Electrically long loop antenna with homogenous near B field inside antenna loop

I wanted to know is it possible to create a loop antenna that functions in a way like a high frequency helmholtz coil. Because a helmholtz coil is usually made with multiple turns of wire having high ...
Girts's user avatar
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Numerical calculation of the Electric field in a system knowing the potentials on the contour

I have a problem in numerically determining the electric field lines given the potential in a system described in the photo. The electric field vector E is related to the potential at a point with the ...
Franc's user avatar
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1 answer
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How does a Current Injection clamp work from a physics persepective?

Current injection clamps are normally described as a transformer with a single turn secondary, which is all fine and good, but the construction of a transformer is different from a current clamp. ...
EricEverton's user avatar
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Can a photon be modeled using AC driven electron and AC driven wire loop?

Can a photon ("electromagnetic wave packet") be simulated in software as an electron bouncing up and down (for the oscillating E field) and a loop of electrons with neutralized electrostatic ...
user323947's user avatar
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0 answers
30 views

How to predict the efficiency of a very low speed Railgun Actuator/Lorentz Force Actuator?

Well, I read somewhere that the slower the railgun is, the higher its efficiency, so I started trying to find out what would be the efficiency of a railgun actuator to move a heavy object (3000kg) at ...
Fulano's user avatar
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2 votes
2 answers
580 views

If electromagnetic waves are indeed created by a changing electric and magnetic field, then why don't we see magnet based antennas?

I understand that exciting electrons, basically freely moving electrons cause electromagnetic waves. The faster they accelerate the higher the frequency of the waves. If this is indeed the case, then ...
Vishwa Mithra Tatta's user avatar
4 votes
4 answers
1k views

Can a slanted magnetic field be created with this insulated stranded wire arrangement?

I am considering building a small-scale experimental coil gun because I have an idea of how a magnetized projectile could be rotated while it is traveling through the coil(s), similar to how a bullet ...
WaterSparkle351's user avatar
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39 views

TM transmission coefficent derivation

Please help, I have exams and I am not sure if my derivation for transmission coefficient for TM case is correct.
Cillantro's user avatar
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Can the formula for magnetic field intensity be used for cores with varying cross sectional area?

Can the formula H = NI/l be used for cores with varying cross sectional areas?
Kurt Thomas's user avatar
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Can I use electromagnet to hold a cabinet door shut while driving (in my campervan)?

I have a bathroom/kitchen cabinet in my camper van that I keep forgetting to close correctly before driving away. Then in the first corner it'll swing open. I was wondering if I could use an electric ...
Joel's user avatar
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2 answers
85 views

Self Inductor - Where do I go wrong when calculating the EMF?

I have the following problem : I have a self inductor L. Its characteristics are L = 10uH and R = 12Ohm. If a current I = 200mA DC goes through L at t = 0 decreases to 1mA in 100ns, what would be the ...
R Strem's user avatar
3 votes
3 answers
218 views

Deflection of current in a metal plate conductor

If I have a metal plate (square in shape) and an electric current moves from one side to the other. I understand that most of the current will take the path of least resistance but all paths will be ...
Daniel's user avatar
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1 answer
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Finding the velocity and current on a 'moving' resistor [closed]

I came across this example which to me looks kind of non-sensical. I think the Hall effect is supposed to be used to help solve this, but I struggle to use it as I think that there is some information ...
Vuko Mijušković's user avatar
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2 answers
97 views

EMF Meter: difference between AC magnetic, AC electric, and RF Measurements

let's consider this EMF Meter. Regarding its description, I have some doubts regarding what it is physically trying to measure: Detects all three types of EMF pollution: AC magnetic, AC electric, and ...
Kinka-Byo's user avatar
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Magnetic field generated by a current-carrying wire

When dealing with the magnetic field generated by a current-carrying wire, the formula for the magnetic flux density is B = μi/2π·d, but what if the point is located on the wire it self? In this case ...
Ahm2025's user avatar
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How are the currents induced by the E-field and H-field flows on a sphere? [duplicate]

Please correct me if I am wrong? We consider a sphere made of thin metal, with a radius of 1 m, at 20 km distance from an AM transmitter operating at 1 MHz. The alternating current in the transmitter ...
HAPU's user avatar
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1 vote
1 answer
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Would tempered glass be a good material to use within this simple axial flux permanent magnet motor?

I am in the design phase of building a simple axial flux permanent motor, and I am wondering if I should use a piece of tempered glass as both an insulating material and as part of the motor's frame. ...
WaterSparkle351's user avatar
0 votes
2 answers
127 views

Re-Magnetizing A Magna-Tip Screwdriver Handle

See what I added to the bottom of this question Sorry for the high school level question. I would rather not spend my time experimenting. I have a quality gunsmith screwdriver set. The set contains ...
B. Varner's user avatar
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1 answer
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Radar's radiation inside air traffic control tower [closed]

As a person working in a tower cab on which a ground movement radar is installed, I am curious what the typical power flux density would be inside the cab due its proximity. The frequency of the radar ...
logicWP's user avatar
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Magnetic Force Between 3 parallel conductors

I have a problem with 3 parallel conductors carrying currents, as shown in the picture. I need to determine the force per meter length acting on the bottom-right conductor (carrying current I2). I ...
TheDegman's user avatar
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1 answer
37 views

Phase shifting 2 waveforms to create a rotating magnetic field

I'm trying to set up a rotating magnetic field with 4 electromagnets coils (2 pairs) arranged around a fluidic cell. I have read that you need to shift the 2 waveforms out of phase by 90 degrees to ...
LeviB's user avatar
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9 votes
3 answers
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Would reducing the air gap between the rotor and stator to micrometer/nanometer scale distance proportionately increase a motor's power?

I'm asking this because the smaller the distances between electromagnets, the stronger the electromagnetic field. I don't know if this would mean a proportional increase in power, be it either torque ...
Fulano's user avatar
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2 votes
2 answers
275 views

High Switching Coil Current Circuit

I've been working on building a circuit designed to handle a 40 A current with a switching time of less than 1 ms (currently using 500 us). I've attached the circuit for your review. Initially, I ...
Nim4eng's user avatar
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2 votes
3 answers
154 views

Measuring magnetic fields in the 1-10 Hz range

I apologize in advance but I am a chemist just venturing into the world of electrical, so you may need to explain to me like a 5 year old. I have a chemistry project that involves the use of AC ...
LeviB's user avatar
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0 answers
60 views

What is the consideration when installing or replacing the shaft of an induction motor?

Here are two picture of my washing machine's motor. I am not sure whether you still have such that machine in your country. It is a top loading washing machine's washing motor (a another smaller one ...
AirCraft Lover's user avatar
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measuring and characterizing magnetic field of pulsed electromagnetic coil

I'm trying to measure the characteristics of a kinda-high-powered pulsed electromagnetic coil. I'm trying to characterize different coil designs, and different pulse-generators. It's operating between ...
zmcginty's user avatar
2 votes
3 answers
119 views

Why are signals reflected from an antennas dish as opposed to being absorbed?

I am trying to learn in the area of electromagnetic noise ect. I see online that a Faraday cage can work without been contected to ground (like the ones found on radio PCBs.) It sort of makes sense to ...
George kirby's user avatar
-1 votes
2 answers
3k views

Power supply makes a static/coil whine noise when the power supply is off and the PC is off

I have noticed that my power supply (PSU) makes a VERY slight coil whine/static noise while it is plugged into the power outlet, regardless of the power status of the PC and the PSU. It sounds no ...
P. Z.'s user avatar
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0 votes
2 answers
135 views

Reluctance concept

I would like to appeal question, where the correct answer was given as option (B) 'Cross-sectional area.' However, I believe that option (D) 'Permeance' is also inversely proportional to reluctance. ...
Dragnovith's user avatar
1 vote
2 answers
164 views

Electromagnet design and powering it up? (Fault prevention of DC supply for a small coiled Electromagnet)

I want to create an array of multiple electromagnet which I will be controlling using a microcontroller. I will have around 100 such magnets lined in a squared grid 10x10. Only three or five at a time ...
Kush_Uttam's user avatar
1 vote
4 answers
404 views

Is ferrite core inductance similar to iron?

My 0.5" (1/2 inch) iron core inductor did not have a high inductance due to (I assume) eddy currents. Theory seems to suggest that ferrite cores are the ticket to increase inductance. I ordered ...
zdanman's user avatar
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0 answers
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Antennas Far field radiation pattern

I want to understand this Far field graph of an antenna generated in CST, from the picture: Is this a good radiation pattern? If yes, then how? How to explain the graph?
Trisha Das Mou's user avatar
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0 answers
26 views

ISO permitted RF emission spectrum for medical devices in hospitals

I've been searching to find the electromagnetic compatibility requirements for medical devices to be used in hospital but cannot find the correct ISO standard. The list here only lists implantable ...
SeanJ's user avatar
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0 votes
1 answer
89 views

What happens when a three phase motor designed for delta connection is run star-connected? [closed]

What happens when a three phase motor designed for delta connection is run star-connected?
Sabare alam Khan's user avatar
2 votes
3 answers
129 views

Don't understand a symbol in this circuit

I'm trying to fully understand this circuit. I don't understand how the connection from the power source is going into the center of this coil. What does this represent? The circuit is for an ...
3nigma_'s user avatar
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0 answers
65 views

Why is a magnetic encoder required to detect orientation of BLDC motor?

In the well known “Smart Knob” project: https://github.com/scottbez1/smartknob an magnetic encoder is used directly below the brushless gimbal motor to detect the orientation of the motor. But why is ...
NickC's user avatar
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1 vote
1 answer
151 views

Forms of Magnetic Noise Coupling

I was watching a video of Bob Pease discuss magnetic coupling of noise into the ground lead of an oscilloscope probe. See video at 5:40 https://www.youtube.com/watch?v=2vzvWUqUtb8 I noticed another ...
mrbean's user avatar
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1 vote
0 answers
35 views

How to determine the length of a quarter wave transmission line which would be added to an existing circuit for impedance matching?

Are the values I have calculated accurate? With this setup, there seems to be a 90 degree phase difference across Tx2. I'm not sure if the 90 degree phase shift is supposed to across just Tx1 or ...
Manav Ganesh's user avatar
1 vote
2 answers
108 views

I am wondering if magnets can be safely used to connect power from one to the other? [closed]

I am thinking of trying to create a extension cord that can be taken apart or separated as needed. And rejoined at any length of cord but connected only through magnetic connections. So I'm wondering ...
HEO's user avatar
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0 votes
0 answers
39 views

Toroidal/cylinder single turn transformer to circular waveguide coupling

The questions is mostly in the title. Is it possible to effectively couple a toroidal/cylinder shaped ferrite core with thick spread out single turn of wire to a circular waveguide? The idea is that ...
Girts's user avatar
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2 votes
3 answers
412 views

Scattering matrix of quarter-wave transformer

I am trying to solve for the scattering parameters of a quarter wave transformer. The example that I am given is a transformer with characteristic impedance 100 Ohms, and the reference impedance (...
ff18192021's user avatar
0 votes
1 answer
75 views

Multimeter range

I've been using a small multimeter meter and the problem is that anytime I want to measure amperage that exceeds 200 mA, I have to switch the red probe the 10 A port. Unfortunately, I can't get the ...
imran muhd's user avatar
2 votes
2 answers
194 views

Visualizing current flow in transmission line

This may be a trivial question, but I am not sure how current flows in certain types of transmission lines. Consider for example a coaxial cable working in its TEM mode. The wave travels perpendicular ...
fraghotmailcom's user avatar
3 votes
1 answer
258 views

Time-Varying Inductance in Electrical Systems

How to derive and solve equations for electrical systems when the inductance of an inductor is not constant and changes over time? I'm familiar with the standard equations like E = 1/2Li^2 or V = Ldi/...
MohammadAli Zeraatkar's user avatar
0 votes
1 answer
126 views

Design of an antenna on a PCB card emitting between 1000 and 5000 Hz

I would like to create an antena on my PCB thanks to copper track. My antenna has to be a square like a coiled coil in order to emitt a magnetic field. Is it possible to create an antenna like that ...
Bouboubi's user avatar
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0 votes
1 answer
203 views

How does current flow in a circuit with a capacitor, Can you please explain the concept of displacement current

When a capacitor is coupled to a DC source, current begins to flow in a circuit that charges the capacitor until the voltage between the plates reaches the voltage of the battery. How is it possible ...
Confused's user avatar
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7 votes
3 answers
1k views

When an electromagnetic relay is switched on, it shows a dip in the coil current for a millisecond but then increases again. why?

I am currently studying the effects of current on the coil of an electromagnetic relay and came across this graph: Image source: Ramirez-Laboreo, E., Sagues, C., & Llorente, S. (2015). A new ...
Syed Muhammad Ghufran's user avatar
2 votes
4 answers
824 views

Spending money on gold cables [closed]

Recently a friend of mine spent several tens of euros to buy a set of gold connectors to connect to the audio amplifier, justifying this expense on the grounds that they were gold and therefore the ...
KaleM's user avatar
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