Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
2answers
36 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 ...
1
vote
1answer
62 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 ...
2
votes
2answers
71 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 ...
0
votes
0answers
45 views

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 ...
0
votes
0answers
26 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.
0
votes
1answer
47 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, ...
2
votes
0answers
65 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, ...
-1
votes
3answers
86 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.
0
votes
2answers
170 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 ...
0
votes
1answer
55 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: ...
-1
votes
1answer
28 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 ...
0
votes
0answers
16 views

How to choose contour when finding magnetic flux density?

In this question, how we decided to use such this contour? Also, why integral (B dot dl) the outside and sides parts are zero? At the outside part; contour and B are parallel, because of their dot ...
0
votes
2answers
39 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 ...
1
vote
1answer
52 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!
0
votes
2answers
98 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 ...
1
vote
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 ...
0
votes
1answer
83 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 (...
0
votes
1answer
64 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 ...
1
vote
1answer
35 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 ...
0
votes
3answers
64 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 ...
-1
votes
0answers
29 views

Measuring a magnetic field using a loop

I am trying to use a loop to measure oscillating and pulsing magnetic fields. Using Faraday's Law (N - number of coil turns, B - magnetic field, A - area of coil, t - time) I should be able to ...
4
votes
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) ...
0
votes
2answers
134 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 ...
1
vote
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 ...
0
votes
4answers
67 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 ...
-1
votes
3answers
239 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: ...
-1
votes
1answer
75 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 ...
-6
votes
3answers
108 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 ...
0
votes
2answers
90 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. ...
1
vote
0answers
39 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 ...
0
votes
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 ...
0
votes
1answer
73 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 ...
0
votes
2answers
41 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 ...
0
votes
3answers
47 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 ?
1
vote
2answers
72 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 ...
0
votes
0answers
39 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 ...
0
votes
1answer
126 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 ...
0
votes
1answer
39 views

Permanent magnet generator tooth width

I am thinking about designing a radial flux permanent magnet generator. However, I could not find any information about determining the tooth width. Should the tooth width be all the way the same as ...
0
votes
1answer
50 views

Lenz Law and Magnetic fields in an Inductor

Hoping somebody can set me straight on the magnetic fields involved in an inductor when the current is changing. This is how I see it: The source current has a magnetic field. This changing flux ...
-2
votes
1answer
113 views

Energy in induction furnaces [closed]

I have seen a question in my exam today and I don't know the real answer and need an explanation. Energy conversion in induction furnaces: heat -> electric energy -> magnetic energy electric ...
-3
votes
2answers
77 views

Electric field around a current carrying conductor?

The picture shows the direction of the magnetic field around a current carrying wire. I wonder what will be the direction of the electric field with respect to the direction of the magnetic field ? I ...
0
votes
1answer
31 views

U Electromagnet Optimization

I have a U shaped magnet (like the one we used to see in school, half red half blue) that I want to make out of it an electromagnet by winding around it a 0.5mm diameter insulated copper wire, ...
0
votes
1answer
52 views

E-Mag Biot-Savart law (line current - Magnetic field)

I am taking an electro-magnetics course and I have these problem. When I found the alphas values (\$\alpha_1 = \frac{3}{\sqrt{13}}\$ and \$\alpha_2 = 0\$ because of the infinity line). The equation ...
0
votes
0answers
42 views

EMF - DC Permanent Magnet Motor

I am using FEMM to design a dc permanent magnet rotor. I am trying to calculate the EMF that is induced to the rotor. Since each coil has a different position, the induced emf will be different. In ...
1
vote
0answers
137 views

Finding the equivelent capacitance of the circuit

Finding the equivelent capacitance of: simulate this circuit – Schematic created using CircuitLab I think that it should be: $$\frac{1}{\frac{1}{C_1}+\frac{1}{C_2}}+\frac{1}{\frac{1}{C_3}+\...
3
votes
0answers
138 views

0.5 tesla solenoid

Alright, I am supposed to make a solenoid (water cooled) having 0.5 T field at the center. The solenoid should be ideal so we are supposed to make the length of solenoid quite large as compared to ...
2
votes
1answer
185 views

Build a horn antenna for 10.525 GHz

I want to build a Horn antenna to increase directivity of HB100 sensor and I studied principles on an Antenna's book. I started from a void rectangular waveguide. Since the frequency is 10.525 GHz, ...
1
vote
0answers
323 views

Electromagnetic pendulum (pulse movement)

I would like to make a cost effective (without using large circuit and micro controller and all) electromagnetic pendulum for my wooden clock (so the second wheel will move according to pendulum ...
0
votes
1answer
48 views

How to move a magnet to a specific coordinate on a board

I was just reading about Claude Shannon's famous maze-solving mouse, Theseus, which used a movable magnet under the maze to draw the mouse in a given direction. I'd like to play around with this idea. ...
9
votes
4answers
2k views

Why no macroscopic electrostatic electromechanical parts?

So, I understand that relays, motors, and other electromechanical devices are almost always electromagnetic devices. Why is this? I know that electrostatic motors exist, but what makes them ...