Questions tagged [electrical-engineering]
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24 views
Question about the purpose of a transistor [migrated]
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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0answers
32 views
Adequate Power Supply for 300 Daisy-Chained LEDs [migrated]
I have 300 LEDs (ws2812b) wired in a series. They were sold as 150 LED/5 meters and rated to power at 9W/m, so 45W/5m strip. I would need 90 Watts to power my entire 300 LED strip. I have a 3-rail ...
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0answers
19 views
Open circuit voltage gain of JFET transistor circuit [migrated]
So this is one of the questions from my previous past papers, I worked out my Vgs and Vds value correctly (-1.25v and 10v). However, when calculating my open circuit voltage gain, I use the quetion Av=...
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0answers
10 views
Operational amplifier characteristics [on hold]
What are the differences between the Open and Closed loop gain of an operational amplifier? Also, what is the concept of “feedback resistance” in amplifiers?
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1answer
73 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
22 views
Zener diodes-Quantum tunneling
Hmm Hello .I would like to ask something about the operation of zener diodes.
We have the diagramm of quantum tunneling:
If a particle has to pass a potential barrier and after the potential barrier ...
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0answers
12 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 ...
0
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1answer
24 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 ...
0
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0answers
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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0answers
17 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 ...
2
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1answer
37 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?
0
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1answer
51 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
69 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
83 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 ...
0
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2answers
61 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 ...
3
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1answer
32 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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0answers
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 ...
0
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2answers
74 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 ...
0
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1answer
18 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
84 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
50 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
39 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
48 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, ...
0
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2answers
96 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.
...
0
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1answer
47 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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votes
3answers
215 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 ...
0
votes
1answer
38 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 ...
0
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1answer
41 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
43 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
53 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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0answers
68 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
72 views
Why diodes can be used to create a current-independent voltage drop? [duplicate]
How is current independent of the voltage drop in a diode?
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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 ...
0
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2answers
45 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 ...
0
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1answer
37 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 ...
2
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0answers
50 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 ...
0
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1answer
13 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, ...
1
vote
1answer
26 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 ...
-2
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1answer
51 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 ...
-2
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1answer
52 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 ...
1
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1answer
70 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?
0
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1answer
111 views
Potential difference between two points
Okay so this might sound kinda stupid but I'm new to electrostatics and I was doing a question that asked me to find the potential difference between two points . Now I calculated the potential at the ...
0
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1answer
27 views
Electrical potential with a combination of bodies
1) what would occur with respect to electrical potential if a +1 charged body is brought close to a -2 charged body?
2) a positively charged body next to an earthed conductor
For the 1st one I'm ...
0
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1answer
445 views
What happens to potential when a charged body is placed next to an uncharged conductor?
I know that the potential of the charged body decreases due to induction however I feel as though I need a more in depth answer. Why does induction cause the potential of the charged body to decrease ...
0
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1answer
38 views
Problem regarding phase difference in Transmission lines
In order to find impedence variation in Transmission line(T.L.) we usually draw Smith chart(it is a complex reflection coefficient ($\Gamma$) plane on which constant resistance and reactance circles ...
