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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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How to find force pull solenoid

Sorry for the previous post that was wrong. I want to know F=(NI)^2*μ0*A/2L^2. What is the cross-sectional area? Reference.
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Find force pull solenoid

Sorry for the previous post that was wrong. I want to knowF=(NI)^2*μ0*A/2L^2 A What is the cross-sectional area? NewRef.https://www.researchgate.net/publication/...
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why the mmf created by armature current in dc machine is triangular in nature?

Why is the mmf created by armature current in dc machine triangular in nature? I have read but not understood. the graph's picture is also being attached here.
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How does a electropermanent magnet work?

I’m trying to wrap my head around electropermanent magnetism. I read this wonderful PhD Thesis by Ara Knaian as well as details the history of this concept as well as Kyle Gilpin, Ara Knaian, and ...
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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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4answers
66 views

How is electromagnetic interference possible when measuring voltage difference?

This question is primarily concerned with audio but it's probably applicable to other areas as well. As far as I understand, EMI is caused by electromagnetic waves adding power to wires as they ...
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4answers
4k views

Why does magnet wire need to be insulated?

What is it about having multiple coils that enables the magnetic field? Why can't I just have one big wire or threaded wire on a motor? Sorry, it's kind of a baby question but I couldn't find the ...
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1answer
72 views

Why does adding more coils make my electromagnet weaker?

I've built a couple of simple electromagnets, using a nail (not sure of the material) and copper wire connected to a 1.5V AA battery. I'm really confused because the electromagnets with less coils are ...
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1answer
97 views

Treadmill causes nearby electronics glitch

I don't know if it is right place to ask, if not correct/guide me. I recently have built treadmill workstation, where I could walk and work (rather than just sitting). But as soon as I turn on ...
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2answers
67 views

How do I convert the units of a moving magnetic field to volts?

Copper wire wrapped around an iron core produces current when a strong magnet is moved in its vicinity. I gather the "magnet movement" part is expressed in units of "weber" (kg⋅m2⋅s−2⋅A−1) or perhaps ...
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0answers
22 views

Which power converter topology has higher benefit of EMI/EMC?

Which power converter topology can be best suited for EMC compliance for small power converter to be used in LED lighting products. In my context I'm using a 5W non-isolated AC-DC converter which is ...
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1answer
51 views

Magnetic material demagnetization through Curie temperature

It is known that some materials lose their permanent magnetic properties when they are heated above certain temperature known as Curie temperature or Curie point. As those materials are cooled down to ...
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4answers
92 views

Sinusoids represented using Euler's formula notation, confusion

EM plane waves are represented using the equation (ignoring amplitude) $$E(x,t) = e^{j (wt - kx)}$$ They are also represented in this form: $$E(x,t) = \cos(wt - kx)$$ I want to get the electric ...
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2answers
58 views

Learn how information is transmitted

Maybe this is not the right place to ask this, it is so, please tell and I will delete this question. I want to learn how information is transmitted using radio and TV. I want to learn that because I ...
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1answer
125 views

How to generate a high energy electromagnetic wave? Using high voltage or high current?

I am about generating an electromagnetic wave which should be powerful enough. So I should manipulate its electric field and magnetic field simultaneously. As far as I know E amplitude depends on the ...
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2answers
45 views

Magnetic Flux loss in PM Motors

The PM motors specially BLDC or PMSM they get their armature energy from the permanent magnets on their rotors unlike the Induction Motors in which the armature gets its energy from the Stator ...
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1answer
81 views

Contradicting ideas about differential signal route, confining fields vs Increasing impedance

By initial sense I think we must: keep pair intra-distance as close as possible for field cancellation. Fill surround of pair with GND plane and have via near to it to confine the fields, prevent ...
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2answers
83 views

“Electromagnet 5kg DC 3V 5V 6V 12V” - what do these multiple voltages mean?

I wanna buy an electromagnet from aliexpress and many of them are lifter magnets and have 6V, 12V, 24V and 5kg. So if i choose the 6V option does that mean the magnet can lift 5kg at 6V? Why would ...
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Why aren't homopolar generators more commonly used?

In particular with the advent of HVDC(high voltage direct current). Using mercury(metal), the resistive losses can be greatly reduced. There has even been some experimental research into neon plasma ...
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27 views

Air core design

what is the appropriate air core design for inductive power transfer that is suitable for 30khz? I used 200 turns and 7 inches diameter.
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1answer
52 views

What happens in a generator so that we get a sinusoidal voltage as an output?

I read this online, " For a travelling magnetic field in a circle, the induced magnetic field in the armature of the generator will be sinusoidal. That's why the generated voltage is a sinusoid, ...
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0answers
68 views

What it the base technology used in electronic speaking pens?

I am interesting to learn more about the technology used in electronic speaking pens which can be found as education toys for small children. When the pen is placed over a book illustration or text, ...
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3answers
102 views

What is the SI unit of magnetic force?

As derived from F = qvB sinθ, what is the unit of magnetic force, and why? Edit: I mistakenly asked about magnetic field before. -- I'm asking the magnetic force.
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2answers
190 views

Explain this circuit

I know this circuit is an oscillator circuit and it senses another signal of same frequency, but I don't understand the calculation behind it, and the reason for emitter inductor, 3.9k collector ...
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1answer
105 views

Practicality of using flat-spiral coil as electromagnet?

For my project, I'm using a 3D magnetic sensor to track the proximity of a local electromagnet at any time, no more than a finger length away. Ideally, I would like the the electromagnet to be: ...
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1answer
30 views

How to determine direction of induction current (I inc) according to V emf?

In this question, I easily understand the solution. But I want to determine the direction of induction current (I inc) with the Lenz Law. I know how works Lenz Law, but I couldn't determine the ...
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2answers
45 views

Determining magnetic flux density of a closely wound toroidal coil

I am using David K. Chengs's Fundamentals of Engineering Electromagnetics book. In chapter 5/question 5.2, there is a given closely wound toroidal coil, and it asks what is the magnetic flux density ...
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1answer
71 views

How to convert A/m to dBμA/m?

Lets say I have -2 dBμA/m as a limit. How do I convert the magnetic field strength in A/m to dBμA/m? Is it as follows? $$20\cdot \log(\frac{ |H| }{10^{-6}})$$ Thank you!
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2answers
107 views

Why does my laptop emit electromagnetic radiation when charging (only)? [closed]

I have an electromagnetic radiation detector that I've been playing with recently, going around the house and testing various appliances, and I noticed something weird. When I charge my laptop (or ...
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1answer
77 views

Current flowing through copper wire?

I am a grade 12 student, working with electromagnets for a physics project. My equation requires me to measure the current of a 20-25 cm bare copper wire 18 gauge. The power supply would be an aaa ...
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1answer
96 views

Can a magnet cause a microwave oven to unsafely radiate energy?

I've already successfully warped the colors on a large old CRT Television by setting unshielded speakers on top of it. If I understand correctly, this was due to the deviation of the electro-magnetic (...
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1answer
188 views

Calculating number of coil turns for a generator

I'm building a generator for a school project. I'm planning to use N42 neodymium magnets with performance of 5100 Gauss, How do I calculate what diameter of copper wire I need to make the coils and ...
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1answer
45 views

Is EMF induced in a conducting loop moving in a uniform magnetic field with uniform velocity perpendicular to the magnetic field?

Due to the the magnetic force= q(v × B), the separation of charges must take place. One point must be at high potential than the other. So can't we just take the separation of the charges as the ...
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3answers
73 views

RFID: Why is inductive coupling used instead of EM waves for LF and HF systems?

Is it because of antenna sizes? At 900 MHz a 1/2 dipole has a size of around 15 cm. That would be far higher for 125 kHz, so instead we use coils to power the transponder and use load modulation for ...
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3answers
3k views

Bad effects of coiling electrical cables [duplicate]

I have a desktop computer and a lot of external hard disk cases. I coiled all cables to make them organized and easy to clean. But an electrician told me; if you are using a cable, coiling (wrapping) ...
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2answers
159 views

DIY electromagnet using copper wire and AC adapter

I want to make for some demonstration (caching some paper clips on ON and doping them on OFF) electromagnet made from copper wire (should it be single wire?) with ferromagnetic inside coil: As power ...
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1answer
97 views

Why we can't copy car remote patterns?

I have a set top box remote that I can use to control set top box as well as TV by using the set button on my stb remote.That remote can copy any remote IR pattern but when I tried it on a car remote ...
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4answers
76 views

The fields and waves associated with a transformer

Induction in a transformer happens via a fluctuating magnetic field in coil A inducing a voltage and hence current in coil B. An electric field is associated with a fluctuating magnetic field. Is ...
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3answers
241 views

Does the phone transmit waves? [closed]

In a cellular connection, How much is power density (in W/m2 or mW/cm2) of the RF energy from the phone to the tower? If not possible in above units then can I know in dbm ? My phone has: Head SAR: ...
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1answer
110 views

What is the main difference between AC and DC generator basic working principles? [closed]

I cannot understand the main difference on AC- DC generator basic working principles. Lets consider how a loop wire works with a magnetic flux inside a DC generator briefly. Whenever the sides of the ...
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3answers
110 views

can we generate electricity from earth magnetic field? [closed]

can we generate electricity from earth magnetic field? As we know that earth behaves like magnet having two poles ..and according two Faraday law changing magnetic flilux causes emf ...what if I roate ...
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2answers
91 views

Can I use rectified AC current to heat an object inside a induction coil?

The reason why I would like to use rectified AC is because I want to keep the magnetic field inside the coil unidirectional. A changing magnetic field induces current in the coil and vice versa. ...
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0answers
45 views

Alternate formulation for the Neumann formula

I'm currently learning about the Neumann formula for the calculation of the mutual inductance between thin current filaments. However, for future purposes I want to find an alternative formulation of ...
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1answer
42 views

Ohmic power loss due to electric field

Recently I read in the basic EM theory course , that the Ohmic power dissipated in a conductor is directly proportional to the conductivity and the square of the electric field intensity , but we know ...
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1answer
79 views

If counter-emf is zero, why is COE violated?

I've been modeling this thought experiment a for a while now: If in a electromagnetic system, the induced emf wasn't opposing the change, but increasing it, we're getting energy from nowhere, that ...
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2answers
44 views

Circuit to control a magnetic field, using a laminated core

I need to produce a magnetic field that goes from 0 - 80 kA/m (0 - 100 mT), which I can control the amplitude of, and change its polarity. The diagram below outlines a couple of pieces of laminated ...
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3answers
48 views

Magnetic field direction

How do I know the direction of magnetic field produced by a bar magnet, assume a electron present side to the magnet ?
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2answers
77 views

Is this phenomenon capacitive coupling or human antenna effect?

I injected a 90 MHz signal into an electrical cable via a signal generator. And I used a spectrum analyzer to measure the signal strength of 90 MHz at the other end of the cable. Then I found the ...
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0answers
41 views

What keeps a delay-off timer energized when you cut off the power?

I've come to understand the function of the delay off timer as follows: When it is energized, it instantly changes its contacts. And when you "de-energize" it, it delays for a preset time and only ...
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1answer
195 views

How can I measure AC magnetic field using linear hall effect sensor with the arduino?

I have a SS49E hall effect sensor. I want to measure magnetic field in gauss using arduino analog output. I have a code for analog application but is this appropriate just for the dc magnetic field ...