Questions tagged [electrical-engineering]

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35 views

Reason of saturation region in MOSFET

I can't wrap my head around the circumstance that, somewhen when I increase $ V_{DS} $ the current $ I_{DS} $ will remain constantly. Why is that? https://www.electronics-tutorials.ws/amplifier/...
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5 views

Max frequency of Helmholtz coils

What is the max frequency achievable with helmholtz coils? And is the magnetic field as strong as a dc electromagnet or does it lose strength with the increase in frequency?
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0answers
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Electromagnetic field propulsion [closed]

Assuming that we have a metamaterial that can slow down the velocity of propagation of changes in an EM field to around 15 000 m/s (without felling or applying any forces), can we build a propulsion ...
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0answers
11 views

How to simply explain correlation between Range, Power and Bandwidth in RF Technologies?

First off, I don't have a great understanding about the physics behind radio frequency technologies. I'm working on a paper evaluating if LoRa infrastructure can help developing communities for a ...
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0answers
52 views

Does the “electricity saving box” work? [migrated]

https://electrical-engineering-portal.com/the-real-truth-behind-household-power-savers concludes Power factor correction devices improve power quality but do not generally improve energy efficiency (...
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1answer
90 views

How is Alternating Current (AC) used in Bipolar Junction Transistor (BJT) without ruining its operation?

In a BJT (Bipolar Junction Transistor), say NPN in common base configuration, we forward bias the Base-Emitter Junction and reverse bias the Base-Collector Junction when using a constant DC supply. ...
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0answers
32 views

Oblique incidence over a stratified medium - the transfer matrix is not unitary?

As you've read on the title, my problem is about an oblique incidence problem over a stratified electrical medium. I've made a quick sketch with the incidence on the first layer. Let's suppose that I ...
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1answer
53 views

What is causing the acceleration of charges in an ideal TEM transmission line?

As I understand, in an ideal TEM transmission line we can set up the telegrapher equations and solve to show that the line propagates voltage and current waves. My confusion arises when we recognize ...
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0answers
5 views

OPAM (when non-inverting terminal is open) [migrated]

What will be the output voltage in OPAM when one end (non inverting terminal) is open? (for circuit see the attached figure) The way I was trying this question was like this: for any arbitrary value ...
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0answers
47 views

How point-contact transistor work?

In December 1947 Bardeen, Brattain and Shockey introduced a device which is considered to be the first transistor. This transistor was point-contact device. So, it used metal-semiconductor junctions. ...
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1answer
34 views

What is the purpose of a resistor in an OR gate?

What is the purpose of a resistor in an OR gate? Isn't it useless since the gate works even if the resistor is absent?
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1answer
18 views

How to connect a computer with something like a little electric car? [closed]

I am a complete beginner and I wondered how to hardware like a controller with a f.e. little electric car. So when I want to program a controller like a ps4 controller so that it can let a little ...
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1answer
28 views

Parallel grouping of batteries

While studying 'Parallel grouping of batteries with internal resistance' I came across its derivation and found that the equivalent emf to be Σ(E/r)/(Σ(1/r)) Why didn't we take the equivalent emf as ...
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2answers
105 views

What do capacitors actually do? [closed]

I’ve read answers on Quora about why capacitors are used, and they all pretty much said they store charge, or filter out specific frequencies. But what does that actually mean? What do you achieve by ...
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4answers
90 views

What is the purpose of Thévenin's theorem on equivalent circuits? [closed]

What is the purpose of Thévenin's theorem use if there are multiple formulas and theorems available for solving a circuit like KVL, mesh, nodal, etc?
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1answer
29 views

Signal reflections on conductors at low frequencies where they are not transmission lines

This question might be suited for the Electrical Engineering forum, but I think I might get more scientific explanation/discussion (rather than anecdotal) on this forum. Is the reflection phenomenon ...
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0answers
39 views

What are these white pellet in my speaker used for? [closed]

These are the pics of the speakers in my surface laptop. What are these white pellets used for. Similar pellets can be found in many tiny speakers of iPhones and Samsung phones.
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2answers
48 views

How to show connection between measured data (sound in $\rm dB$) and the size of speakers? [closed]

How can we relate the measured data of speakers with its SIZE (speaker)? I have the data on white noise and pink noise (FFT and 1/3 octave), I'm a bit confused about how to show the relationship (...
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2answers
25 views

What is the difference between horizontal units and horizontal scale at an oscilloscope?

This is a picture of the data of a given measurement by an oscilloscope. I would like to know what the difference between horizontal units and horizontal scale at an oscilloscope is. I would be so so ...
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1answer
51 views

Physical Meaning of Joule Integral

I have been reading literature on fuses and came across the joule integral or $i^2t$ value many times. Often, it is referred to as energy but I am confused because shouldn't energy be $E=RI^2t$? I ...
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1answer
47 views

Can we make a motor without a permanent magnet and with wireless energy transfer? [closed]

If we could transfer energy wirelessly with 100% at short range. I think we could then use the energy to power an electromagnet from the stator side. So we wouldn't need a permanent magnet at all but ...
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2answers
23 views

Doubt about the impedance of the Instruments

It is correct to say that the instruments that measure signal have a large impedance as opposed to the instruments that generate signal, whose impedance turns out to be small. I know that this is true ...
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1answer
35 views

Where does the whine of electric engines come from?

In my city, electric motorbikes are becoming very common and I have noticed a high pitched whine coming from their engines when accelerated. How is this sound produced? Why electric cars are not that ...
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1answer
26 views

Which device we can use in place of relay for 35000 volt? [closed]

What can we use in place of relay for very high voltage and current supply switching (let's say 35000 volt).
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1answer
52 views

Why is n-p-n transistor typically “faster” than p-n-p transistor?

I know that the n-p-n transistor is faster than p-n-p transistor. My book explains it with 'the hole is faster than an electron. But I think the hole is empty space of electron, so these speeds should ...
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0answers
10 views

How does forward biasing of both junctions in BJT leads to saturation?

As far as I know, for an NPN-BJT, when both (base-emitter and base-collector) are forward biased; we consider the operation to be in saturation mode. Here, the transistor functions as a short circuit ...
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0answers
15 views

Is Collector current depends on width of base and Vcb in forward active mode? (common base transistor)

I asked this question on electronics.SE but I don't get any good answer may be because its more of a physics question . I just started reading about transistors from book "Microelectronics ...
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2answers
44 views

Why are ultrasound devices using ultrasound?

I wonder why ultrasound devices are using ultrasound. Is it a biological reason due to our human audible range? Or is there a physical reason for that?
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0answers
58 views

Generating very large area gamma rays by other ways other than large accelerators

According to this link https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf, HERMES III at Sandia National Labs can generate very large area gamma rays by converting the electron beam into ...
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0answers
17 views

Bandwidth of a RLC Circuit

Bandwidth of an RLC circuit is defined as the angular frequency difference for which Power dissipated through circuit is half of that dissipated at resonance. What is so special about this range that ...
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1answer
110 views

Will an appliance metal case get alive if touched by the neutral wire?

My phyiscs textbook only discusses what will happen if a live wire touches a metal case and how it turns alive, however, I was wondering, will the same effect happen to the metal case if touched by ...
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1answer
29 views

What could be the meaning of “illuminance” in this home device?

I bought a Xiaomi sensor that measures light intensity. The data I get from it is called illuminance_lux and the unit is supposed to be ...
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0answers
28 views

Why is the worst case input/output impedance of an $RC$ filter $R$?

I'm going through the Art of Electronics in my spare time, and I ran across a problem I've been scratching my head about for a few days. The book states that in the worst case for any $RC$ filter, the ...
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1answer
46 views

Why is it hard to cool a mini-PC to room temperature?

I have this passively cooled mini-PC that froze every few days. After a lot of investigation I realized that it was overheating (running android studio and such) so I bought a fan, an arduino nano and ...
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0answers
19 views

Energy bands motion in an npn transistor

How do electrons move in an npn transistor along their energy bands, in active mode? How does the base current originate in this energy diagram?
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1answer
14 views

When the excess electrons move to equalise themselves in a negatively charged conductor, can it result in positively charged atoms?

i am a beginner in physics and am currently studying electrical engineering. I was wondering when the excess electrons move to equalize themselves, can it result in some atoms being positively charged ...
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2answers
72 views

Physics vs Electronics (Smartphone charger)

Basically, an electric charger consists of a transformer, which transfers electrical energy from one inductance to another.. َAs i imagine the process physically the first circuit (inductance) should ...
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3answers
150 views

What is the name of the shape of the iron core in a transformer?

I'm researching on transformers and curious to know about what this shape is called (the actual core block, ignore the wires around it).
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0answers
8 views

Do dielectrics feel significant magnetic force?

If we apply an high frequency ac magnetic field to a very dielectric material (order of millions) with very high refractive index (order of thousands) does it experiences any significant forces?
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1answer
32 views

AC field propulsion

Assuming that we have a metamaterial that can slow down the velocity of propagation of changes in an EM field to around 15 000 m/s (without felling or applying any forces), can we build a propulsion ...
0
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2answers
53 views

Is the performance of electronic devices affected by their age? [closed]

I always wondered what happens inside an electronic component during its lifetime. I am aware that passive or active electronic devices can have their performance decreased over a long period of ...
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1answer
27 views

Highest refractive index dielectric

What is the material or metamaterial that is a very good dielectric and has a very high refractive index at least in frequencies below $500\ MHz$?
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0answers
35 views

Attenuation in microwave and optical communications

I have read that the attenuations of microwave transmission lines and optical fibers are ~1 db/m and ~ 0.2 db/km, respectively. I understand that these values depend on the geometry, design, and ...
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1answer
28 views

Do electrons on $n$-side loses its energy to fall into holes on $p$-side during forward bias in a diode?

So in a diode in forward biased condition the electron from n side recombines with the hole in p side.I also understood that the electrons in n type are in conduction band and holes in p type are in ...
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3answers
77 views

Why does the power remain constant during the stepping up and stepping down of current in transformers?

I understand quite a bit of transformers, their structure and other concepts and formulas related to mutual induction. However I'm not able to explain why the electrical power has to be constant ...
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1answer
23 views

With a half-wave rectifier, wouldn't the charges accumulated on one side?

In a normal alternating current circuit, the charges just travel back and forth, so they won't accumulate. However, if only half wave can pass through, then will the charges get accumulated on one end ...
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0answers
31 views

Does writing a file to a solid state drive change the mass? [duplicate]

Some stupid meme my sister showed me went along the lines of "will my laptop get heavier if I put more files in it?", but it was sufficient to get me thinking--is there an energy change &...
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1answer
54 views

in photoelectric effect, where do electrons go when they are ejected from metal?

When light shines on a metal, electrons are ejected from the surface of the metal provided the energy of the photons are greater than the work function of the metal. My question is: Where do the ...
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0answers
13 views

Reducing current of a driver cell in a potentiometer

In a potentiometer in order to reduce the current from the driver cell shoudn't the resistor be connected in front of the positive terminal rather than behind it?
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0answers
24 views

In an AC Current, if the voltage is high, does this “amplify” the radiowave emissions without changing the frequency?

Hello My question comes from my interest in antennas i suppose: I understand that antennas utilize alternating current to generate EMF Waves along a particular frequency depending on how quickly the ...

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