Questions tagged [field]

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1answer
62 views

Does this sensor measure electrical or magnetic fields (with oscilloscope)

I want to measure electrical and magnetic fields of the frequency 50Hz to 1MHz with my oscilloscope. For electrical fields I learned that any bunch of metal will work. For magnetic field derivation ...
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2answers
37 views

Magnetic field of a coil composed of stacked coils

Basically my question is that if you have a coil with N turns with its ends connected to a source of current (I), and you have another coil which is N number of single coils stacked on each other with ...
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0answers
25 views

Parabolic wave equation, electric and magnetic field definitions

The split step solution for Parabolic Wave Equation (PWE) applied to the tropospheric propagation problem is: $$u(x+\Delta x, z)=e^{ikM(z)10^{-6}\Delta x}\mathfrak{F}^{-1}[e^{\frac{-ip^2\Delta x}{2k}}...
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0answers
22 views

Electric Field in a Multi - Cell Cavity

let's consider a multi cell cavity like this one. The image has been taken from here. My question is about the magnitude of the electric field inside it. Let's consider each single cell of this ...
1
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1answer
48 views

Interface conditions and surface current density

let's consider the interface condition for magnetic field strength: 1) I do not have a clear idea of what js represents. If I have understood it correctly, it is a linear density ([A/m]) of a surface ...
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2answers
47 views

Floating Conductor Next to AC Power Source

Let's say I have a conductive metal sphere connected to a 50Hz 1kVrms AC Power Source referenced to Earth ground. About 3cm away, there's an identical metal sphere suspended by a non-conductive ...
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1answer
87 views

Does a pcb as patch antenna isolate itself?

I'm currently working on a prototype patch antenna for UHF. Since I'm out of copper at the moment, I used empty PCB's as base material (don't mind the PCB in between, it's only a spacer): So now my ...
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1answer
49 views

Magnetic Monopoles and Magnetic Current Densities

I see that in electronic engineering the Maxwell equations are written with also some terms which represent the magnetic charge and the magnetic current densities. I was told they are inserted only to ...
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0answers
59 views

Alternator field winding VS equivalent inductor

I have a question which I know is going to be more opinion biased than factual. I know this isn't the purpose of the forum, but I would really appreciate some extra opinions so I'm going to ask it ...
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0answers
45 views

Should I daisy chain start connect or wire separately?

This is related to field wiring schemes and interference. Sometimes tens of transducers are needed to be coupled to a single-ended data acquisition board's analog input channels where the transducers ...
3
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1answer
114 views

Detrimental impact of magnetic field on PCB and battery?

We are developing a small consumer electronics product consisting of a small 4-layer PCB along with a few PDM microphones and BLE chip/ an antenna, as well as a LiPo battery. We are locating a small ...
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3answers
1k 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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1answer
108 views

Understanding oscilloscope pattern

This is likely an obvious question for anyone with professional experience but I'm just a humble software engineer trying to fathom the mysteries of my oscilloscope... I created a simple square wave ...
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1answer
33 views

What determines the direction and cause of electric field exerted on test charges?

-I understand when there is an on-going electric field, if it is produced by a positive charge, the direction of electric field is away from it etc. And, if we get a +ve test charge, it repels it, and ...
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1answer
70 views

use battery to generate weak electric field?

i am a biology student interested in how marine animals react to weak electric fields. My professor and I want to do a trial experiment and were hoping to rig something up ourselves for cheap. Is ...
0
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1answer
62 views

Enhancement type MOSFET - channel formation

In an enhancement type MOSFET (an n channel one assumed here), when a positive gate to source voltage is applied, the holes of the substrate near the gate move deeper into the substrate away from the ...
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1answer
190 views

Question on MOSFET - small signal model

In the small signal model of a MOSFET, the current from the drain to the source (for an n channel MOSFET) is a function of the gate to source voltage only. But, if a positive voltage was not applied ...
2
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1answer
125 views

How to extract energy from an alternating electric field?

Given an alternating electric field E inside e.g. a big parallel plates capacitor, how can you make use of the field's energy to power an electronic device? So far I thought of putting two smaller ...
0
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1answer
42 views

E fields and M fields in Near Field

I am reading a textbook that mentions that small loops with high dI/dt on a PCB tend to produce predominantly magnetic waves and stubs with high dV/dt tend to produce predominantly electric waves in ...
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0answers
57 views

What is the direction of electric field inside a battery?

Outside the battery, in the conductor it is in the direction of conventional current. But what about inside? Somehow linked: For p-n junction, at the depletion region which side is at higher ...
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3answers
499 views

Solenoid's field intensity calculation dependency on width/diameter of coil?

Textbook formula for field intensity in solenoid coil is H = (N * I) / l H magnetic field intensity in ampere-turns NI ampere-turns l is length between the ...
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1answer
85 views

How to excite a fluorescent lamp without connecting it?

I'm a newbie in electrical engineering, so this might be a silly question. But are there any standard ways to create an electric field over a volume of air, strong enough to excite a compact ...
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5answers
6k views

How does a capacitor resist changes in voltage?

I was reading about how capacitors work and two sentences confused me: "A capacitor’s ability to store energy as a function of voltage (potential difference between the two leads) results in a ...
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1answer
61 views

Strong H fields: electronic items susceptible to thier damaging effects and how to shield them

This is another question related to magnetic fields. I'm trying to determine the thickness of copper foil that would be required to shield common electronic items from H fields of about 133 A/m over ...
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4answers
294 views

What is voltage exactly? [duplicate]

First, let me start off by saying that I have read the answers to this question (which is the same as mine), but the answers basically explain the different ways voltage is created or compare it to ...
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0answers
31 views

Electrical field of cathode ray

In my study book of radio frequency engineering is a question, which is pretty odd in my opinion. Calculate the electrical field of a cathode ray for the cases r < d and r > d. There are two ...
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3answers
2k views

How does the range of bluetooth increases by adding an antenna?

I have seen too many tutorials on how to increase HC-06 bluetooth module range. They all involve cutting the on-board antenna and adding an external one (a piece of wire or a 2.4GHz antenna). I was ...
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3answers
1k views

Disposable camera EMP coil not producing any field

I recently took on this project: https://www.youtube.com/watch?v=WIMhraVcdTg Trying to use a disposable camera as an EMP generator. I wrapped my wire around a bottle, but it still won't do anything,...
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2answers
95 views

Electric Field electrical charge

Hey i dont know how to solve this. Can somebody help me? In the two-plate arrangement shown in the sketch, there is homogeneous electrical field strength $$\vec{E_0} = -\vec{e}_y * 10\frac{kV}{cm}$$ ...
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1answer
141 views

Is Work done to Transfer Energy?

The example below is for a perfect lossless circuit with no resistance for the sake of illustration only. In reality this does not exist, but again the purpose is for simplicity. If there is 1 Joule ...
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1answer
75 views

Does my electric clearing field actually make ions?

I am using an electric clearing field of 15v/10cm (~150V/m) to remove ions from a test chamber, however I'm wondering to what extent the localisation of the field's reference voltage plays a role. ...
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2answers
267 views

EMI Field Strength

I tried to look up this kind of question in the archives but didnt find much usefull information. I also have another question in regards to EMI but I will ask this later in a seperate post. ...
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0answers
126 views

Equipment to measure strong constant (in time) and slowly changing electric fields

I would like to measure the electric field in the vicinity of an object of interest. I would like to have decent spatial resolution (i.e. be able to pinpoint a measurement to a point in space within ...
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2answers
147 views

How does current flow inside a grounded coax shield?

I have been trying to reconcile the fact that current flows on the inside of a coax shield with the common practice of grounding the shield. These ideas seem contradictory at the moment. For a 2-wire ...
2
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3answers
263 views

Help me understand electrical fields better

I have a hypothetical scenario that would help me better understand (I hope) electrical fields and propagation of electrical fields better. So let's have a super simple circuit with one voltage ...
-1
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2answers
83 views

Would the Electric Fields of simultaneously transmitted waves affect eachther

If there are 2 waves, with different frequencies, wouldn't the Electric fields add up and impact both waves regardless of the frequency difference? I attached a picture of what I mean, when there are ...
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1answer
64 views

Find error in mathematical proof of electromagnetic fields

This is wrong but I can't figure out what is wrong, could someone help me find the errors.
2
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1answer
156 views

Antenna design for radio energy emission into a fresh-water test tank

I would like to emit as much RF energy in the frequency range of 433.9 to 434.5 MHz into surrounding fresh water with a 100mW transceiver. The antenna is in the middle of a 4mx8mx2m fresh-water tank ...
1
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2answers
2k views

Does a simple bug detector detect electric field or magnetic field?

Hi. This is a very cheap and simple bug detector that is supposed to make sound when it detect RF signals between 100Mhz-2600Mhz. I found out that it doesn't do what it supposed to do,since its ...
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2answers
159 views

Can an electric field have Electric potential difference with only one charge?

I know that when you have a charge, it creates an electric field that is equipotential. So, can you have potential difference without adding another charge? Maybe putting a material across the ...
0
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1answer
315 views

How can a battery have electric potential?

Electric potential is the potential energy of a charged particle in a point in space relative to another point in space in an electric field, all that divided by the charge of that particle. I don't ...
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3answers
289 views

Is electric field of capacitive sensing circuit harmful and is it radiation?

I have constructed a circuit for capacitive sensing. The code charges and discharges a conductive plate. This uses an Arduino which is connected to a computer via USB. I have decided to measure the ...
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3answers
290 views

how does negative differential resistance in a PCT work?

I understand that up until a point (Vforward), the differential resistance is positive. And then it turns negative, and as the voltage increases, the current decreases, as you can see in this IV curve ...
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1answer
891 views

Capacitive Coupling Between Adjacent Conductors

I have been unable to find a definitive answer to my questions after some extensive browsing online. My question involves the coupling between two adjacent conductors (wires, PCB traces, etc) due to ...
2
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1answer
73 views

\$2n\$ point charges on a circle at \$O\$, what's total electric field intensity \$\overline{E}\$ at \$\pm 1\mathrm{m}\$?

The problem reads is from a Schaum's Outlines of EMFT and reads: A total charge of \$1\mathrm{nC}\$ is equally distributed among \$2n\$ points which are placed equidistantly on a circle with \$1\...
4
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2answers
369 views

What is the nature of the near field at a receiving antenna (excited by a far-away transmitter)?

Near and far field are usually explained for transmitting antennas, but since antennas are reciprocal, I would expect a receiving antenna to have a near-field phenomenon. 1) Does the impinging field (...
4
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1answer
203 views

Detecting atmospheric voltages on high altitude balloon

Our High school is launching a high-altitude balloon payload and the experiment we want to perform is the detection of atmospheric voltages. My friend and I were amazed when we saw this video where ...
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1answer
134 views

What is the concept behind speed change in a constantly loaded DC series motor?

I have a problem regarding DC motors that I am trying to solve. I think that I might not understand the assumptions that are given. The question given is: A DC series motor is connected to a load. ...
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1answer
92 views

Electrostatics - Calculating the vector of electric field

Most of the problems I run into while studying electrostatics are ones regarding a charged thread for which I need to calculate the vector of the electric field. The thing that is confusing me is how ...
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1answer
1k views

Help me understand EM Field behavior around Ferrite sheet

I designed an NFC reader board that reads and writeS to tags. Some of the parts with NFC tags have metal frames inside them (think of cup holders with NFC tags, but the object in the cup holder can be ...