# Questions tagged [field]

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### BLDC Hall Sensor Angle Offset

I'm running a BLDC motor and I'm working on my own Software. I want to run the BLDC Motor with field oriented control, that's why I need a precise electrical angle. I'm using three hall sensors in the ...
• 1
60 views

### Is this circuit measuring the electrical field?

I have found the following circuit on the web (https://electroclinica.org/2018/03/23/fabricacion-de-un-sencillo-medidor-de-campo-de-rf-diy/) which claims to be an "RF field" detector/meter/...
46 views

### Calculate the active and reactive power of the connected load after field increase in synchronous generator

A 3-phase synchronous generator connected in Y configuration has the following given parameters $V_L=38kV, R_a=0.3\Omega,X_s=2\Omega, S=360MVA, cos{\phi}=0.83$ Where the parameters correspond to ...
97 views

### Helmholtz coil - I don't understand the circuitry

I work in a testing laboratory. We recently introduced in our repertoire a testing method using Helmholtz coils to generate a magnetic field. In order to have a magnetic field I need to have current ...
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105 views

### Why is the magnetic field not blocked by the copper wires in a current transformer?

When I want to protect an electronic board from a magnetic field generated by a transformer, I put a circle of vias (as a jail grid) connected to GND planes to stop the magnetic field. How does a ...
• 27
94 views

### Help understand the role of an inductor and its value (educated guess)

This circuit is a part of a field strength meter circuit in an old magazine, the value of inductor J1 is unknown (due to a print error in the magazine.) The circuit works like this: With S1 open and ...
• 477
118 views

### Distribution of surface charges along the wire

Distribution of surface charges with a constant gradient is present along the length of the wire which produces a constant electric field along the entire length of the wire. This results in constant ...
160 views

### How many newtons are there in one coulomb of charge?

Or, I should have said, how many newtons of force does one coulomb of charge exert? At a distance, presumably, of one meter? Since N/C is supposedly equivalent to V/m? P.S. What are the values for a ...
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1 vote
83 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 ...
913 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 ...
• 103
273 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 ...
267 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 ...
1k 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 ...
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166 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 ...
1 vote
712 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 ...
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44 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)
71 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 \...
• 551
391 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 ...
• 101
101 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 ...
• 479
1 vote
580 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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76 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 ...
120 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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1 vote
165 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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143 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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1 vote
70 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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338 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 ...
4k 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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1 vote
195 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
44 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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1 vote
92 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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426 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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1k 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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180 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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63 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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71 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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1 vote
968 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 ...
• 334
113 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 ...
15k 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 ...
68 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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431 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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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 ...
5k 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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1 vote
2k 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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1 vote
97 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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144 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 ...
79 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. ...
380 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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1 vote
161 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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436 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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