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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23 views

Work done by the Lorentz force? [migrated]

Im trying to calculate the work done on a single wire placed inside a magnetic field. Now for the force I've used the Lorentz force formula to calculate it, for the distance should I used the width of ...
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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
56 views

electromagnetic levitation

I'm trying to create a platform that utilizes electromagnets to levitate an object. Very similar to what has been done in this product. It's very difficult to deduce how the magnets are positioned ...
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0answers
42 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 ...
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1answer
39 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 ...
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0answers
23 views

Reflection coefficient as a function of frequency [migrated]

I am trying to relate the equation for reflection coefficient in oblique mediums to the frequency but can't figure out how the frequency affects the reflection of light. \$n_1\$= intrinsic impedance ...
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2answers
64 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
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1answer
40 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
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1answer
40 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
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1answer
152 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
65 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
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1answer
41 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
56 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 ...
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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
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0answers
34 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
63 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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0answers
83 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
30 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.
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2answers
140 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
96 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
39 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
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1answer
40 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
120 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
87 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 ...
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2answers
138 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
62 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
138 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
61 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
72 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
129 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
83 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
78 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
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0answers
76 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
59 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 ...
7
votes
2answers
528 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
120 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
62 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
84 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 ...
2
votes
3answers
153 views

Is Back EMF relevant in dynamos, where there is electric generation?

While doing some research about dynamos, I came across a situation wherein there was a question about the validity of my dynamo design. The counter to the design I suggested was that there would be ...
0
votes
2answers
154 views

A cubical LC circuit

I would like to solve for currents through inductors and the voltage across capacitances of the attached circuit. I am trying to figure out a correct method to solve such circuits which could have the ...
0
votes
0answers
73 views

2mm linear actuator (electromagnet, hydraulic, etc.)

I am currently trying to make an idea become a reality, but I do not have a background in the electrical engineering, I am in fact a Software engineer. I have been searching a lot for a 2mm x 2mm x ...
-1
votes
2answers
64 views

What are evanescent fields?

I am not able to understand what is the origin of the evanescent field, how do they interact and what is the physics behind it.
1
vote
2answers
134 views

How does the shape of the coil relate to the magnetic field around it?

I want to know if the shape of the coil affects the path of the magnetic fields around it. The two different shapes that I have are Helical coil and a spiral coil (in a plane).
0
votes
1answer
302 views

How to make a simulation for wireless power transfer circuit in HFSS (High Frequency Structural Simulator) software?

I want to simulate a circuit of wireless power transfer consisting of two resonating coils along with a loop with each coil. I am stuck with introducing a coil in HFSS.
0
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2answers
50 views

Is there any simulation software that can be used for simulation circuits of wireless power transfer?

I am searching for a simulation software that also shows the interaction between electromagnetic waves in a wireless power transfer setup.
0
votes
1answer
73 views

Can magnets break LED notification light on phone? [closed]

I'm posting this question here because it's about magnets and electronics. Please tell me if it's better suited to another site! I've been messing around with some reasonably strong magnets around my ...
1
vote
2answers
87 views

How to make an effective electromagnet?

I am making a speaker with some neodymium magnets and about 3m of copper (insulated) cable. How would I configure this to make it loudest/best electromagnet?
1
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0answers
53 views

Electromagnetic interference in a Car

I am currently working with a 12 volt inverter to power EL tape. The tape is wired in various places in my vehicle, I have tested it in my car and I hear a high pitched noise on my radio when I try to ...