Questions tagged [field]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
3answers
59 views

If greater potential energy is toward pos charge, then why PN energy band diagram show lower energy toward pos charge across depletion region?

If in an electric field, greater potential energy and voltage are toward the positive charge and away from negative charge, then why do PN energy band diagrams indicate lower energies toward the ...
10
votes
4answers
817 views

Construction for a homogeneous field using permanent magnets

Please let me describe what I am trying to achieve and I will pose my question in the end. I am trying to design a small chamber which can have a uniform magnetic field inside. I want to see if a ...
2
votes
2answers
95 views

What causes the electric field to change over series resistors?

So for example if we have a a wider and a narrower wire of the same length in series, since v1A1=v2A2, in the narrower wire the charges will move with a greater velocity. Since v is proportional to ...
-1
votes
2answers
70 views

Relation of drift velocity and electric field?

So I attached the standard derivation of the relationship between drift velocity and electric field. My problem is: Tau=s/Vd, where s is the mean free path of the electron. Substituting this into the ...
7
votes
1answer
712 views

Sewing machine motor repair

I'm a sewing machine mechanic, trying to increase my electric motor knowledge. I have a Bernina 830 sewing motor where the carbon brushes ran down and the wire damaged the commutator and ran a groove ...
1
vote
0answers
38 views

Field Coil Help - Varnish, cotton, wrapping etc

I am restoring a 1940s sewing machine. The motor wire war in really bad condition and needed replaying. I take off the wrapping on the coils to solder some new wire. The wrapping that was used was ...
0
votes
1answer
39 views

How to detect a magnetic field from a distance?

I want to detect a magnetic field, like those of small neodymium magnets, from at least 6 inches away (the further the better, I'd like at least a foot but I won't ask for too much). I'd like to do ...
0
votes
2answers
62 views

A very basic question about PLC field input switches

Below shows two simple ladder logic examples written for a PLC: As far as I understand, the -| |- and -|/|- above are the symbols we write for the PLC not the actual input switches. But we also need ...
-1
votes
1answer
40 views

Transistor Electric field [closed]

For unbiased transistor, is the maximum electric field larger in the emitter – base junction or in the base – collector junction? Why (draw)
0
votes
0answers
40 views

What are the chain reaction that create the electromagnetic wave?

From my very limited knowledge I know that an electromagnetic wave is created by some chain reaction of accelarating/oscillating electric and magnetic waves, I also know about how the electromagnetic ...
0
votes
2answers
68 views

Why is \$E_1=\frac{F}{q}=\frac{K\frac{Q_1 Q_2}{x^2}}{Q_2}\$, instead of \$=\frac{K\frac{Q_1 Q_2}{x^2}}{Q_1}\$?

I have a question about these electric field strength formulas Why is \$E_1=\frac{F}{q}=\frac{K\frac{Q_1 Q_2}{x^2}}{Q_2}\$, instead of \$=\frac{K\frac{Q_1 Q_2}{x^2}}{Q_1}\$? \$K\$ is constant \$=9 \...
2
votes
1answer
109 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 ...
0
votes
2answers
50 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 ...
1
vote
0answers
29 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}}...
0
votes
0answers
25 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
vote
1answer
159 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 ...
0
votes
2answers
51 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 ...
0
votes
1answer
97 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 ...
1
vote
1answer
72 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 ...
0
votes
0answers
73 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 ...
1
vote
0answers
51 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
votes
1answer
155 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 ...
-1
votes
3answers
2k 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.
1
vote
1answer
126 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 ...
1
vote
1answer
34 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 ...
1
vote
1answer
77 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
votes
1answer
99 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 ...
0
votes
1answer
288 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
votes
1answer
138 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
votes
1answer
50 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 ...
0
votes
0answers
58 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 ...
1
vote
3answers
565 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 ...
0
votes
1answer
94 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 ...
3
votes
5answers
8k 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 ...
0
votes
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 ...
0
votes
4answers
343 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 ...
0
votes
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 ...
0
votes
3answers
3k 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 ...
1
vote
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,...
1
vote
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 $$\vec{E_0} = -\vec{e}_y * 10\frac{kV}{cm}$$ ...
1
vote
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 ...
0
votes
1answer
76 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. ...
0
votes
2answers
283 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. ...
1
vote
0answers
137 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 ...
1
vote
2answers
184 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
votes
3answers
264 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
votes
2answers
84 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 ...
0
votes
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
votes
1answer
159 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
vote
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 ...