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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3answers
51 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
11 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
170 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
66 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
81 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
136 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 ...
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2answers
58 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
48 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
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3answers
72 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 ...
-6
votes
1answer
136 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
vote
1answer
78 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
vote
1answer
107 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
vote
2answers
76 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
46 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
43 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
vote
2answers
69 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
45 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
42 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
159 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
71 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 ...
2
votes
1answer
60 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
102 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
votes
0answers
24 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 ...
1
vote
0answers
38 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
69 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
vote
1answer
114 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
34 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.
1
vote
2answers
141 views

Where does radiated power come from?

I've had electromagnetism classes back in uni, but I'm having a hard time linking them with that matter: Take a car antenna -which I assume is simply a wire, coiled or not-, and apply a voltage ...
0
votes
1answer
106 views

Two conductors in a magnetic field, canceling each other's EMF?

If two conductors are in a changing magnetic field, oriented the same in the field, and they induced equal EMF's, can their wiring be oriented in a way that they can cancel each other's induced EMF? ...
0
votes
1answer
41 views

What material is comonly used as insulator in laminations?

I am trying to build a brushless motor for quadcopter use, with a semi-CNC lathe and a CNC mill. I know I can buy a stator core on gobrushless or maybe other place, but I want to know if I am able to ...
0
votes
1answer
43 views

Hall Effect and Magnetoresistors

As per my understanding, When an electric field is applied to a current carrying wire, it exerts Lorentz force on electrons and hence a transverse electric field is generated. Also when we apply ...
0
votes
1answer
132 views

Minimal Hall effect sensor circuit to keep something off after certain RPM achieved

I have a somewhat limited understanding of electronics and circuits. I'm trying to build a circuit that will keep a transistor in an off state after a given threshold of RPM is achieved using a A3144E ...
0
votes
1answer
104 views

Super fast magnetic field by an electromagnet?

Was wondering about the possibility of creating a magnetic field in milliseconds or less? I know it's possible based on certain labs achieving 60-100 Tesla and more. But what about creating a 2 - 5 ...
0
votes
2answers
197 views

Supercapacitors vs. High Voltage Capacitors with Inductive loads used in CoilGuns or Solenoids

I'm looking for some insight on whether an 1000 Farads at 2.7v or 5.5v would be more effective than say 10,000uF at 400v-450v when creating a strong magnetic coil. The intent is something similar to ...
1
vote
2answers
67 views

Magnet in the generator?

I'd like to know if there is some magnet in the rotor or in the stator of the generator? Or neither of those (rotor & stator) need a magnet for the current to flow?
1
vote
1answer
156 views

How to build an H-bridge using MOSFETs? [duplicate]

I want to reverse the polarity of my current source, which is a capacitor in this case, in the middle of discharging phase. Also the capacitor bank is being discharged through a coil to make a short ...
2
votes
1answer
73 views

How to calculate the Induced Voltage Given Spinning Conducting Loop? Intro to Electromagnetics problem

I'm having trouble figuring out a different variation of this problem. On my homework, I'm asked to find the induced EMF for the following B field: $$\vec{B}=50\vec{a_y}$$ I was able to figure out ...
1
vote
1answer
81 views

Magnet strength in dynamo design

I come from a computer background, and apologies if this question sounds elementary. While designing a dynamo, I came across a problem of how to calculate the the strength of the magnetic field, and ...
3
votes
1answer
143 views

What are the bare minimum parts needed to operate a magnetron?

I recently took apart a microwave, and I managed to get a magnetron out of it, as well as a transformer that appears to be the power source for the magnetron, but looks a little small for the ...
0
votes
0answers
18 views

reflection and transmission coefficients when not given information of second medium

I need help with only part (A). I am stuck on this question, i have to find transmission coefficient and reflection coeeficient. I don't know how to get this, I don't have any information from the ...
1
vote
0answers
38 views

Is it necessary for EM fields to be dependent & co-exist in static conditions? [closed]

I was having a discussion today with one my colleagues in the lab about the independence and co-existence of EM fields. My argument: In time-varying fields: EM fields are necessary dependent, and ...
1
vote
2answers
93 views

Solenoid Fail - No Force

I have designed and built a small solenoid and... it doesn't exert any force on the steel bolt I am using as a plunger. I could freely move the plunger back and forth without any resistance. I am ...
2
votes
1answer
87 views

Electromagnet for string vibration

I recently read a lot about guitar sustainers, for those who don't know what are they - it is basically an electromagnet with an amplifier. It takes an input from pickup, amplifies it and then ...
0
votes
0answers
81 views

What is the ideal shape for rail-gun?

I was trying to create a low voltage (30V) rail-gun. I have quite a hard source of power that doesn't drop voltage upon current drain, further more, this source is re-inforced by big Tesla capacitors. ...
0
votes
1answer
61 views

How to get an object charged?

I want to create electrostatic force between two isolated objects which are 3 meters apart from each other. The electrostatic force should be very noticeable, so I want to get the objects charged ...
8
votes
2answers
625 views

How does this iPhone app measure the power flowing through an AC appliance cord?

My electric utility released an iPhone app called "DTE Insight" which (among other things) measures the amount of power flowing through an appliance's power cord by asking you to hold the cord against ...
0
votes
1answer
156 views

Why does the speed of the Electromagnetic wave in the material depend on the frequency of the wave where as they are constant in vacuum (freespace)?

I am confused on why would the propagation speed of any EM waves at ANY frequency is constant in the free space (vacuum) but they seem to disperse in any other materials as the propagation speed of EM ...
1
vote
1answer
70 views

Can a solenoid have its magnetic field “focused”?

Imagine a solenoid generating a magnetic field. Can this field be focused so that it exists only in a certain section of that solenoid at a given time. If a typical solenoid looked like: ...
0
votes
2answers
96 views

Help with a ring launcher

I'm not sure if this is the right place to be asking this question, so close it if it's not, but I need help on a physics project. My current project is a ring launcher (Elihu Thomson Apparatus). I ...