Questions tagged [field]
The field tag has no usage guidance.
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40 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
40 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 ...
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0answers
55 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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0answers
71 views
Evolving a very simple E-field detector
I'm looking into non-contact solutions for detecting charge (even through certain casings) in passive components.
This circuit:
is from this site, it works and I've experimenting with a go/no-go ...
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3answers
128 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
94 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
31 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
63 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 ...
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1answer
44 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
69 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 ...
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1answer
97 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 ...
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1answer
39 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
55 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
314 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
69 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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4answers
2k 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
59 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
231 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
29 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
1k 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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1answer
591 views
Disposable Camera EMP coil not producing any field, why isn't my coil working, is it incorrectly winded?
I recently took on this project: https://www.youtube.com/watch?v=WIMhraVcdTg
Trying to use a Disposable camera as a EMP Generator. I wrapped my wire around a bottle, But it still won't do anything, ...
1
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2answers
89 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
138 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
68 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
191 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
105 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
104 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 ...
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3answers
260 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 ...
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2answers
82 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
135 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 ...
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2answers
1k 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
152 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 ...
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1answer
308 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
254 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
276 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
757 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
65 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
266 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
178 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
132 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
82 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 ...
0
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1answer
94 views
What happens when I put a charge inside a conductor that is already in static equilibrium?
I understand how, when a neutral conductor is charged, the charges will repel each other and after the relaxation time will all be distributed in the surface of the conductor.
My question is: after ...
3
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1answer
85 views
Where can I find a good theoretical treatment of conductor shielding?
Suppose one has three current carrying cylinders lying on the same plane. Some of the electric field of the first conductor ends up on the second conductor, which creates capacitance \$C_{12}\$. But ...
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3answers
766 views
Electrical Machines based on Electric Fields
Our teacher asked us this question during the lecture for Power Electromagnetics. We know that Electric Fields and Magnetic Fields are easily transformable into one another. And they are used greatly ...
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2answers
550 views
JFET hidden wires detector
I want make hidden wires (AC, 220V) detector (circuit is below), based on Soviet p-channel JFET transistor КП103, but JFET's now is very rare. Can i replace this JFET by any low-power MOSFET?
My ...
0
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1answer
192 views
Electric field around tape
So, there's a tape with width of 2a, -a on the -y and a on the y, and it very long, penetrating the the plane of picture, it's charge density (dQ/dS) is
σ=σ0 * y /a , σ0 is a constant.
What is the ...
2
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0answers
54 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 ...
2
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1answer
369 views
Why does the Earth's electric field affect things so little?
Starting here:
http://hypertextbook.com/facts/1998/TreshaEdwards.shtml
"Over land the average electric field is about 120 V/m …. Assuming an exponential increase of the conductivity with altitude, ...
