Questions tagged [electrical-engineering]

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23 views

Johnson-Nyquist Noise and the Assumption of a Noiseless Load

I'm a little stuck on a subtlety of RF/microwave design that I find a bit baffling. It has to do with the convention of using of noiseless resistors as loads in circuit noise analysis. I have not yet ...
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25 views

Photonics 2 . Honorarium will be paid for good solutions [on hold]

!can anyone help me for doing this problem? It's related to photonics 2 , one of the courses in mqster of electrical engineering. I have uploaded the picture of the problem
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13 views

Oscilloscope and Multimeter working principle [on hold]

How do Multimeters measure voltage? How do Oscilloscopes measure voltage? Is there any difference?
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12 views

Voltage tunable capacitor?

I am working on a circuit project which requires some capacitor to be dynamically tunable, preferably by an external control voltage. Just wondering if there are any capacitor components in the ...
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21 views

If the current entering a charge preamplifier is a positive pulse, could the output voltage really be a positive pulse?

In this web page: http://physicsopenlab.org/2017/09/27/charge-sensitive-preamplifier/ they show the input voltage to a preamplifier and the output voltage. If I do the quick computation (see below), ...
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1answer
33 views

Force acting on a current carrying hollow conductor within a magnetic field

It is known that when a current carrying conductor is placed within a magnetic field and current flows perpendicular to the magnetic field, a force is exerted on the conductor. In figure 1, a square ...
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0answers
23 views

Simplifying electrical circuits [migrated]

I have looked everywhere, but i can't seem to find a way to simplify this circuit. I wish i could tell you some of my ideas, but i'm really lost here, can someone help me? If you could explain how to ...
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0answers
10 views

Window comparator [migrated]

What happens if we reverse the configuration of diode in window comparator? will it remain a window comparator?
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1answer
18 views

No commutator or rectifier?

Homopolar motors and generators don't need a commutator or rectifier. Are there any other motors or generators that don't need a commutator or rectifier? If so, what are they?
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33 views

Make sound pipe for JSN-SR04T

JSN SR04T is an ultrasonic sensor. It has a large measuring angle 75degrees. I have read that a sound pipe can help the ultrasonic beam to be more focused. I found this https://autosen.com/en/Mounting-...
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2answers
50 views

Why the potential across the voltmeter is not affected by changing metals? How can we prove it?

A voltmeter has both its leads made of metal Cu. When connected across a battery, it measures a voltage V. One of its leads is replaced by metal Au. But the potential across the voltmeter is not ...
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4answers
151 views

Sinusoidal currents in AC circuits

(I had edited this question a number of times but did not receive a satisfactory answer. So I am re-wording this question yet again. The earlier version of this question can be found here : https://...
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21 views

Electronic explained by hydraulic

Where I can find a book or website (or any source) which contain many electric compounds (capacitor, transistor, diode … and more) explained by a flow of water (hydraulic analogy) which is more easy ...
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2answers
58 views

Why brushless DC (BLDC) motors usually have low voltage and high currents? [closed]

I am not an engineer, and neither familiar with motors, so bear with me. :) Thorough explanations needed. :) The question is, why brushless DC motors intended for RC models and possibly paragliders ...
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0answers
27 views

The physics of microwave vacuum tubes

I've searched this extensively, but I couldn't find anything (the only thing I found was this one). I know this question seems to be more of engineering than physics, but I've found some engineering ...
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1answer
62 views

What causes changes in frequency in the Nation Grid electricity supply? [duplicate]

Following the power cuts in Britain this week, we were told that lack of power being generated led to a drop in the AC frequency as shown in this graph: I understand why a stable frequency is ...
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2answers
73 views

Why to use non-inductive resistances in Callendar-Griffiths bridge?

Worsnop in his Advanced Practical Physics for Students states that All the resistances should be 'non-inductive', for in this method it will be seen that the galvanometer is permanently connected ...
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0answers
15 views

Practical Transformer output

I am a junior on Electrical engineering, on one of my experiment, I have yet found any explanation for this: Is there any possibility that a practical transformer would produce a zero real power on ...
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1answer
112 views

5G networks and health concerns

Are there any peer reviewed journals on 5G networks and health concerns? I know very well that 5G radiation is of low frequency and non-ionizing and some concerns are related to the power of the ...
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1answer
35 views

Modelling behaviour of a transformer

I'm looking for a physical-mathematical model to describe the behaviour or working point of a power transformer in dependency on its most critical parameters like oil temperature/heat dissipation, ...
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1answer
64 views

How is quantum physics translated into the world of electronics? [closed]

I remember watching a documentary about early works in quantum physics and how it was essential to the microelectronics revolution and the invention of the transistor. What part exactly helped? Is ...
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22 views

Why RMS for average voltage in AC current? [duplicate]

We write rms formula as $$v_{rms}=\sqrt\frac{\int_a^b[f(x)]^2dx}{|b-a|}$$ I know if we take arithmetic mean average voltage will be 0. So we want all voltage values to be positive. Why don't we do ...
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25 views

Half wave rectifier confusion

I am searching for a good book or link or video that might give some fresh idea about half wave rectifier properties I mean in my book prescribe by my university that has introduced some of the basic ...
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1answer
34 views

Question about the purpose of a transistor [closed]

I've been studying about diodes and transistors and something made me wonder about the purpose of transistors. In the examples we were talking about increasing current by using two batteries with a ...
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1answer
90 views

Why do we have to switch off mobile phones during flight in airplanes? [closed]

During take offs the flight attendant makes sure that mobile phones are switched off (or maybe turned in airplane mode), why is that necessary? (I suspect that there is something to do with physics ...
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0answers
13 views

Reverse bias under 0.7V

Assume we have a diode. Well, I was wondering what is happening if we connect the negative terminal of the battery to the p type region and the positive terminal of the n type region to the positive ...
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1answer
40 views

MOSFET Body terminal

What is the point of the body terminal in a MOSFET. If we assume Vsoure=0, Vdrain>0 then we will have a linearly changing voltage from drain to source. Then if Vgate>0 , depending on the difference ...
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0answers
16 views

Reverse bias voltage drop

In reverse bias , when we go up the breakdown voltage why is there a voltage drop across the diode?.I mean the diode does resist to the flow of charges but when the electrons flow inside the diode ...
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0answers
16 views

Diodes normal polarised with voltage below forward voltage

Assume we have a circuit with a diode and a voltage source . The voltage source has potential 0.4V .If we polarise forward the diode ( p type region connected to cathode and n type region connected to ...
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32 views

Why does applying a voltage through the gate on a transistor help lower the potential barrier?

At the potential barrier, all that atoms are "satisfied"; they each have the appropriate number of electrons in their valence shell since the free electrons on the n-type side fill the holes on the p-...
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2answers
38 views

Current law explained

Kirchhoff's Current Law (KCL) is experimentally proven but what exactly happens?. I have made a model by taking the drude model and adding the interactions between the electrons and the reason why ...
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0answers
22 views

Drude model for diodes

Well I was wondering how we can apply the drude model for diodes.The normal drude model is used on conductors and insulators and since the diode in forward bias is a good conductor(not the best but no ...
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0answers
29 views

Can anyone help me to clear some questions about diodes and transistors?

i don't understand the basic of the working of diodes, because i imagine that if we have a n-p junction and we want to pass current through from side of n region to p region, if we beat the potencial ...
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1answer
99 views

What is energy band gap?

Explanations for graphene's high electrical conductivity often discuss energy band gap. What is energy band gap and how does it relate to the conductivity of a material?
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1answer
137 views

How to calculate total power generated?

I have a circuit with a piezoelectric transducer which converts mechanical energy to electrical. The ceramic is connected to a 1 Megaohm resistor and a voltmeter which reads voltage. If I want to ...
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1answer
187 views

Quantum tunneling in zener diodes

Well Zener diodes operate as a voltage regulator because of the Zener effect-Quantum tunneling . Quantum tunneling is the effect when an electron faces an energy barrier but after the energy barrier ...
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3answers
108 views

RC circuit discharge while being connected to a battery?

I am facing a conceptual problem in analyzing the following situation which was part of a physics exam; A series RC circuit with $R = 200k \Omega$ and $C = 10 \mu F$ is connected to a 5V battery and ...
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2answers
69 views

Multiple frequencies [closed]

could someone please inform me how it is possible to send multiple frequencies down one wire? I’m referring specifically to a communication protocol known as HART. It seems they send a 4-20mA signal ...
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1answer
51 views

Which types of collisions contribute to electrical resistivity?

Do electrons only bump with other electrons in a circuit and that only causes resistance? Or do they bump with the nucleus as well? Here's a post I have been studying recently: The path of a ...
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19 views

Why does nMOS using N+ gate have lower Vth than nMOS using P+ gate ? (w/o band diagram)

I understand it from band diagram.(Band bending is more stiff in N+ gate case) However, I don't know what's essentially happening. If P+ gate and N+ gate have same dose, their poly depetion will be ...
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2answers
173 views

Difference between diode and LED

What is the difference between a diode and a led? I know a led is a diode and I know how they are used and so on but I'm not really sure why a regular is not also light emitting. Therefore, what is ...
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1answer
20 views

What does the phase discriminator portion of the Costas Receiver do mathematically?

What does the phase discriminator portion of the Costas Receiver do mathematically? The output of the $I$-channel is $ \frac{1}{2}A_C \cos \phi \, m(t) $. Which means for small deviation of phase $ \...
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1answer
137 views

How do I connect a four way key in a potentiometer?

How do I connect (which wire to which terminal) a four way key to a Potentiometer to compare the EMF of two cells. Circuit diagram and a four wayway key is shown in the pictures.
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1answer
64 views

Is a radio receiver antenna a capacitor?

I think so, but its capacitance should be very small, so how can the antenna correctly receive the signal, the low capacitance wont bother the signal?
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1answer
45 views

Why can I hear the treble sounds through a speaker, such as on my phone, better than I can with headphones?

I'm not sure if this is related to my hearing loss, or if anyone else has noticed it, but I find it easier to hear higher frequency sounds coming out of a speaker that I hold up against my ear versus ...
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2answers
72 views

How does a sound box amplifier work?

I read in a few places that in a guitar for example, the vibrations are passed through the connectors to the wood and the wood with its bigger surface is more efficient as a coupler to the air, ...
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2answers
258 views

Principle of potentiometer

I could not understand why the emf of the main cell (labelled E) in the circuit (can be a battery eliminator) should be greater than the emf of the cells (E1 and E2) used in the secondary circuit. ...
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1answer
73 views

How to calculate the dispersion parameter of a Fiber?

I am writing a presentation about DCF Fibers. From many articles i am reading, the dispersion parameter of Fibers are given. But it is not shown how it has been calculated. For example ,in this ...
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3answers
224 views

Is there a physical limit to memory reading and writing speed?

Is there a limit to the speed at which a memory, quantum or classical, can be read or written into? I've seen this interesting question : Is there a physical limit to data transfer rate?. Here I'm ...
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1answer
44 views

How would a square waveform effect an acoustic wave?

I recently did an experiment where I tried to measure the properties of an acoustic wave by using a microphone and speaker in a tube. I was wondering how would changing the waveform to a square change ...