Questions tagged [electrical-engineering]

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7 views

MOS Capacitance variation with Voltage [on hold]

Can anyone indicate me about the details of MOS static capacitance variation with applied Vgb (gate to substrate voltage)? what I found in the literature is (afraid not) dynamic capacitance in ...
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0answers
13 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
88 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
34 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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0answers
22 views

Engineering aquatics [closed]

I have a 300 gallon aquarium. The water to the filter system is gravity fed. I need to replace the pump that feeds the water back up to the top of the tank. What size GPH pump should i get in order ...
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1answer
55 views

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

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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0answers
20 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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24 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
28 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
74 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
27 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
15 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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30 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
36 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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20 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
50 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
59 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
106 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
90 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
64 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
42 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
94 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
19 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
91 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
54 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
41 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
52 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
184 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
53 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
219 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
39 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 ...
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1answer
47 views

How do multi-meters measure capacitance?

Many multimeters have the ability to measure capacitance along with the ability to measure AC voltage, DC voltage, current, resistance ... The only equations I am aware of that determine capacitance ...
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2answers
44 views

Need of LED Modulation

I have an experiment of calculating the velocity of light by using phase difference produced (link of the experiment is at the end). The experiment has a control unit which has an LED installed to ...
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0answers
57 views

What is the uncertainty on 50 Hz a.c.?

We are doing an experiment to measure velocity using the ticker-tape timer which runs on a 50 Hz a.c. 12 V power supply. I am in Ireland. So the time interval between each pair of dots is 0.02 s. But ...
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82 views

Why the product of hole and free electron density is constant in semiconductor?

I have learned from a text book of electronics that the free electron density, n (which is equal to that of hole, p) of intrinsic semiconductor due to thermal excitation is a function of temperature ...
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2answers
79 views
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1answer
30 views

DC Battery Charging Question

I have a 7.4v LiIon that hold 1450ma. I have a variable DC bench power supply that I can crank up or down and adjust as needed. I want to quickly charge the battery and noticed if I adjust the ...
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2answers
46 views

Grounding secondaries in isolation transformer

In an isolation transformer (I assume a 220v-110v step down transformer is also called an isolation transformer), you can ground either of the secondary leads. I'd like to know the following: If you ...
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1answer
42 views

What does ground in low voltage electronic circuits mean?

I have been confused a lot by the word "Ground". The ground that I've usually heard about is connecting a wire of appliances with the rod buried under earth but what does the word Ground mean when it ...
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0answers
69 views

Conductivity of a heavily doped semiconductor at Absolute zero temperature

As the Fermi level moves toward the conduction band in an n-type semiconductor; when heavily doped, it moves into the conduction band of the semi conductor. So, will the semi conductor behave as a ...
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1answer
14 views

What influences the variance of signal transmission speed?

I'm currently thinking about the various sources that influence time when it is synchronized with the NTP protocol. One of them is the physical layer (OSI-model). When sending a bit over a cable, ...
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1answer
27 views

How do scintillation detectors work, for gamma ray spectroscopy

So I understand what happens in the crystal with respect to the interactions and how the electrons in PMT are multiplied by hitting dynodes etc. But what I can't really seem to find any information on ...
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1answer
53 views

Bjt configuration

In common base configuration,we know that alpha is almost 1 which means that the base current is almost zero.But what is the physics behind this base current almost equal to 0?And similarly in common ...
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1answer
53 views

Ohm's Law in Practise [closed]

When the AUX pin of a stereo is connected to my mobile phone's audio female port, I just measured the voltage at the end of this AUX pin (No load is connected) approximately 2mV using a DMM. But when ...
6
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3answers
1k views

Confusion about how an electron gun works

I'm a little unclear about the charge balance aspect of an electron gun. Referring to this diagram and similar diagrams I've seen, what I don't get is wouldn't the target of the electrons have to be ...
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1answer
71 views

Why we don't utilize most of the radio or microwave spectrum?

WiFi is from 2400-2500MHz or from 5000-5100. Fm Radio is 87-108Mhz, Phones : 450-3400Mhz But most of the spectrum is "wasted". For eg - Why we don't use above 5Ghz?