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 ...

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47 views

Contactless detection of current

So I'm wondering if it's possible to detect a current passing through a specific cable inside a bunch, without being able to touch the cable at all... In other words : Is it possible to detect the ...
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2answers
61 views

Troubleshooting small home made electromagnet

I used bolt cutters to cut a piece from one of those wire campaign poster sign legs, took that piece and wrapped it (all in the same direction) with wire that was unwrapped from a small fan motor, ...
1
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2answers
65 views

What exactly are surface charges and what do they do?

How does the voltage/electric field of the battery relate to the surface charges on the wire? What determines the amount of surface charge on the wire? (Why more near the battery, less farther ...
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1answer
21 views

Calculating energy accumulated in toroidal coil

That's a cross section of said coil. My question, is since there are two different permeabilities, can I split it into two toroidal coils, with unique permeabilities, or should I've done the ...
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1answer
40 views

Magnet Wire vs Resistance Wire - What's the difference

What's the difference between magnet wire and resistance wire? Which is better for building an electromagnet? Resistance Wire Magnet Wire
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1answer
43 views

Voltage between two points of a square contour in a magnetic field

a,d,R is given. Current of infinitely long wire is \$ i(t)=I \cos(\omega t) \$ I get the flux derive it over time what to do with R? The solution in the book is: ...
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2answers
52 views

How does a synchronous motor know to increase current when the mechanical load is increased?

Consider a very simple singe phase synchronous motor, such as the one shown in figure 1. This motor will not be self starting, but if an AC voltage is applied and the permanent magnet is given an ...
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0answers
14 views

van de graff generator belt related [closed]

I have made a VDG generator with a rubber band as the belt and a glass roller. It doesnt seem to work because I think the rubber band may be conductive. I was thinking of using other materials for ...
0
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0answers
12 views

Magnetic torque on a loop current, nonuniform field

Magnetic torque from a wire of charge. I = 2oA, a=1m. The equation that I think is the one for this problem is $$M=mXB $$ (vector product of moment=I*S and Induction) I tried calculating moment as ...
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0answers
26 views

How to connect a microcontroller to a magnetic coil loop?

I generated a 10MHz square wave from one output pin of a microcontroller using on and off mechanism. I want to give this as an input to the coil.I can connect the output pin to the one end of coil, ...
1
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1answer
121 views

Is the scalar wave phenomenon real, and if so, why is it not much in practical use?

There are a bunch of videos on YouTube describing something called scalar waves (sometimes referred to as "superluminal"). Two examples are this one: Superluminal Scalar Waves for Communications ...
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0answers
22 views

SMD thin/thick film resistor in external Magnetic field

I have an application where the need is to use SMD and MELF type resistors that have tolerance of 0.05%. I prefer the Vishay thin film resistors. Then comes another constrain -> The entire PCB needs ...
0
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0answers
35 views

Same length single wire electromagnet vs multiple wire

This might be more of a Physics question, but I will try it here first.. Today I was experimenting with making electromagnets from 30 AWG copper magnetic wire. I cut two pieces of wire of the same ...
0
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2answers
79 views

How does electricity move when slowed down?

Everything I know about the basics of how electricity works assumes that everything happens instantly, which obviously can't be true since it would violate causality. So say you have a battery and a ...
2
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2answers
275 views

Why does a metal sheet block all noise, but not when wrapped around a cable?

If I place a flat sheet of aluminum foil between a near-field probe and a noisy wire, the sheet completely blocks the noise. However, if that sheet is then wrapped around the wire, it seems to have no ...
0
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3answers
109 views

What kind of electronics (if any) would stop functioning if earth's magnetic poles suddenly switched places?

If earth's magnetic poles suddenly switched places, would electronics continue working as normally? Would there be any visible signs in the electronics that a pole shift has taken place? How about ...
0
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1answer
92 views

Moving a small pin up and down using <12v

Hobbyist here. I'd like to move a pin up and down using <12v. How can I do that. I don't wanna do it the mechanical way as I have three of them. my first option is using a servo in vertical way ...
0
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1answer
51 views

Induced-EMF due to the induced magnetic field of a wire?

If a current carrying wire is placed inside a magnetic field(B), the wire will produce it's own magnetic field that will oppose the applied external magnetic field(B). Due to the two fields opposing ...
0
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1answer
43 views

Forces, on a wire in motion in a magnetic field?

When a wire is placed inside a magnetic field, and current starts to flow in that wire, and that wire experiences the Lorentz force = \$ I\ell\times B \$, and begins to move, aside from Induced ...
0
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1answer
52 views

Why would induced EMF be zero?

If a rectangle loop would move inside a magnetic field, would the induced ϵ be zero? Why would it? Is it due to the induced ϵ canceling out? Being in series and in opposition? If it we're a single ...
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1answer
69 views

What to expect when i place a diode in magnetic field

I am designing a PCB that senses basic NTC values and converts it into digital format. The problem is the entire PCB is above a magnet(about 70mT at the board) that is moving. Hence i want to know ...
0
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1answer
73 views

bipolar linear hall effect sensor choice

ANSWER: This is the best one I found for my purpose mouser.be/new/Texas-Instruments/ti-drv5053-hall-effect-sensor I'm doing a project where I use Hall effect sensor as a proximity meter. Using to ...
1
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3answers
56 views

Net Lorentz force?

From the following diagram: Each (golden) wire is exposed to the magnetic field \$B\$, while as the black wires are not. Assume current supplied from the power supply to be \$50A\$, length \$L\$, ...
0
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0answers
22 views

CST 3-D FDTD simulation

I am working on FDTD simulation of any space. I can work with Matlab and C code for 1D and 2D case but for 3D case it becomes complicated so I want to use CST microwave studio. I want to run simple ...
1
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5answers
191 views

Can an electromagnetic field be created in a non-metallic coil?

OK, so here's a simple one. When current flows through a wire, it produces a tiny magnetic field. If you bend the wire into a spiral, the fields of each loop merge together forming a field you can ...
1
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2answers
69 views

Direction of current flow?

From the following diagrams: Are the current directions correct? Based on where the terminals are connected on both conductors?
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0answers
82 views

Does this article contradicts my textbook?

In my textbook it says that when you apply a voltage to a system the electrons start moving between the atoms in the wires following the direction of the field. Something like this: ...
3
votes
3answers
151 views

Appropriate shapes of an Electromagnet

What is/are the thumb rules for determining an appropriate shape of an electromagnet? By appropriate I mean having a reasonable amount of attraction/repel strength towards metal pieces. If I were to ...
0
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2answers
61 views

Induced EMF of a slope wire?

If a single wire is moving at \$v\$, inside a magnetic field \$B\$, with length \$L\$ then induced EMF is:$$\epsilon\ = -vBL$$ That is for a vertical wire that's motion is perpendicular to a magnetic ...
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0answers
51 views

MHz EF-probe/sensor design

So I have a coil (sender) with a signal of the following approx specifications, for which I want to build an electric field sensor (receiver coil/probe), or alternatively an EMF-probe, if ...
0
votes
3answers
76 views

Effect Of Electronic Devices In Close Proximity

From reading other posts, it seems like electromagnetic induction is the greatest threat to electronic devices these days with either traditional HDDs or newer SSDs. Since current in a wire creates ...
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votes
1answer
142 views

Hendo: Does it need a specific floor? [closed]

Does the Hendo board need a specific floor underneath it? https://www.kickstarter.com/projects/142464853/hendo-hoverboards-worlds-first-real-hoverboard
1
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1answer
88 views

Can AC mains induce a negative voltage in my photodetector circuit?

A smart meter, such as the one in the picture below emits a red light from an LED based on the power consumption (while I was measuring it, it was around 7 sec on 7 sec off i.e. ~0.25kw). The ...
1
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1answer
179 views

How to Run 12v 1A Electromagnet From Arduino (3v) Without External Power Supply

I have a project that I am working on that uses a micro controller to control an electromagnet that I want to run with a 3.7 volt battery. I would like to reverse the polarization on the electromagnet ...
1
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2answers
127 views

Estimate current through inductor in DC circuit with PWM control

I am designing a circuit to control an electromagnet (coil with iron core) through a N-channel MOSFET driven by a PWM signal. I can't figure out how to derive the relationship between the PWM duty ...
0
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0answers
49 views

What does it mean for a voltage to be attenuated by X dB [duplicate]

Say that a signal is passing through a medium, and in the middle of it, the amplitude of that signal drops by 90%, in this case I would just say that the media attenuates the amplitude by X factor. ...
0
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0answers
48 views

Induced EMF of a horizontal wire vs vertical wire?

From the diagrm above, would the horizontal wire induce EMF = -vBL? All of the examples on motional EMF are based on the vertical wire, what about ones that are horizontal that have the same ...
0
votes
1answer
49 views

Two wires induced-EMF?

Is there an induced-EMF from two wires being close to each other (d = 1mm)? I'm assuming since each wire has its own magnetic field. Only in the beginning when current starts to flow and then ...
1
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2answers
77 views

Waveguides: How can you propagate at only one frequency?

In a rectangular waveguide, we know we can find cut off frequency as a function of mode and geometry. Is there a way to design the waveguide so to ensure that we can limit the frequency of ...
0
votes
1answer
52 views

Magnetic flux outside a solenoid perpendicular to the direction of axis of solenoid

I know that using straight forward Biot-Svart law it is possible to calculate field inside a solenoid or at a point on an axis away from the circular coil. Now is it possible to calculate the Flux ...
0
votes
1answer
43 views

How can I combine my knowledge of signal processing with electromagnetic physics? [closed]

Now at University I've learnt both signal processing and electromagnetics, I am curious as to how these two areas can be combined into one. For example, in signal processing you are required to find ...
4
votes
1answer
178 views

Maximizing force of magnetic mass accelerator

I am planning to build a coil gun to fire small neodymium magnets out of a pipe. For this I am planning to use a large 400 Farad 2.7 Volt capacitor. I am wondering how many coils of wire I should ...
4
votes
2answers
75 views

Thickness of low frequency Mu shield calculation

I am dealing with a low frequency varying magnetic field, say 10 - 100Hz with a magnitude of 0.8T. It seems shielding at this frequency gets tricky. Even though Mu is capable of doing it, there should ...
3
votes
1answer
93 views

Standing Wave ratio vs frequency in power transmission lines?

What is the relationship between Voltage Standing Wave Ratio (VSWR) and frequency in context of transmission lines?
1
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1answer
172 views

EM MWD Gap Sub Telemetry Theory Explanation in Drilling Applications

I have been doing an extensive amount of reading on EM (Electromagnetic) Telemetry in MWD (Measurement While Drilling) applications. From my reading, there are a few considerable gaps in my ...
0
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0answers
26 views

plane electromagnetic waves

In free space with no charge, both the curl and divergence of electric field is zero. Plane electromagnetic field exists in such region. Besides plane electromagnetic fields, does any other solution ...
2
votes
0answers
53 views

TV antenna problem: Transmission line problem

I have to solve the following problem: A TV antenna lead-in wire 10cm long has a characteristic impedance of 250 \$\Omega\$ and is open-circuited at its end. If the line operates at 400 MHz, determine ...
0
votes
2answers
73 views

EMF transmission from cell phone's battery

According to Cell Phones & Wi-Fi―Are Children, Fetuses and Fertility at Risk? While one can put the phone in ‘airplane mode,’ which disconnects it from Wi-Fi and the Internet, the cell phone ...
1
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1answer
141 views

Circuit for finding engine RPM using the magneto's coil ground wire

I'm looking to see if there's a solution without using a microcontroller to find the engine RPM (perhaps spark frequency is a better term?) using only the magneto's coil grounding wire. This wire ...
2
votes
1answer
37 views

Does an increase in load current change field winding current?

I would like to know if the current in the field winding of a DC generator using a field winding in its stator increase as the load across the output of the generator itself increases.