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Questions tagged [electronics]

Electronics is the study of electric circuits and electrical components, and the design of useful devices. Some questions in this tag may be more appropriate for the [Electrical Engineering(https://electronics.stackexchange.com/) SE site.

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11 views

Problem in Sequential Digital circuit [on hold]

i want to know that for this circuit do we have to put values of x from least significant digit and also as i have done my calculation can anyone verify the value of z. These are the values i had ...
102 views

Why is contact resistance proportional to $\frac{1}{\sqrt{F}}$ not $\frac{1}{F}$?

See pages 13-15 in "Electrical Contacts: Principles and Applications" for reference. Imagine the following system: Two flat, but rough, surfaces of the same finite area $A$ being brought together. ...
31 views

Diode as a voltage source [closed]

We have known that diodes cannot be used as a voltage source. Eventhough is has a constant barrier potential depending on material used. Why can't we use an unbiased diode as a voltage source?
11 views

Magnetic field dependence of resistance

Experimentally, under the application of an external perpendicular magnetic field, we observe a change in the longitudinal resistance. However, in the theoretical development starting from the Drude ...
13 views

Oscilloscope and Multimeter working principle [closed]

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

Understanding simple LC circuits

I'm trying understand the physics of simple inductor-capacitor circuits such that there is just an inductor L and a cacpacitor C and a switch. Imagine first that the capacitor is fully charged and ...
15 views

What defines a material is an anode or a cathode?

How to know if a material is an anode or cathode? and if i connect an anode and a cathode will it be a diode? Like the pensil razor diode, if it worked not because of that, how does it work?
57 views

Conceptually understanding RL circuits

I'm struggling to conceptually understand the current-time profile of an RL circuit. Specifically, what causes the rate of change of current, $\frac{\partial i}{\partial t}$, to start off high when ...
31 views

In a simple resistor circuit, does the current reach V/R instantaneously?

Essentially, if I were to plot current against time for a simple circuit with a DC cell and a resistor in it, would there be a non-flat profile from time $t = 0$. So, between $t = 0$ and $t = t_1$, ...
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), ...
28 views

Charge preamplifier

A charge amplifier/preamplifier is supposed to have $v_{output}$ proportional to $q(t)$, or proportional to integral $i(t)$. (proof: for example wikipedia : https://en.wikipedia.org/wiki/...
56 views

How important is quantum mechanics to solid state electronics? [closed]

How important is it to know quantum mechanics if one wants a career in solid state electronic devices? I want to do a PhD in semiconductor physics, but I don't know much quantum mechanics. What do ...
21 views

What does mean an electronic symbol of operational amplifier, but with only one input?

What does mean a symbol of operational amplifier with only one input ? See for example : http://physicsopenlab.org/wp-content/uploads/2016/11/CSP.png Does this means that the + input of the ...
25 views

Electromagnetic Waves in a Dielectric [duplicate]

I read that when an EM wave enters a dielectric material, it keeps the same frequency, while its wavelength is reduced, so that their product is a quantity less than c = 3 × 10^8 m/s. Why does it ...
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 ...
10 views

Window comparator [migrated]

What happens if we reverse the configuration of diode in window comparator? will it remain a window comparator?
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?
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-...
15 views

Noise Fundamentals - Johnson Noise

How can be Johnson Noise measured with the help of single electronic instrument (experimentally)?
28 views

Johnson Noise experimental measurement

How can we experimentally find out value (extent) of Johnson Noise of any resistor with certain bandwidth and teperature?
53 views

Phases of current and voltage

Why $u(t)$ and $i(t)$ are in the same phase in a resistor, but in a condensator $i(t)$ is ahead of $u(t)$ by $\pi/2$, and vice versa in a coil? Note: I need physical explanation, like main reason of ...
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 ...
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 ...
15 views

Hydraulic analogy for electrical compounds

I want a source (website or a book) where there are hydraulic simulation (or analogy) for all (or at least the most useful) electronic compounds?
20 views

Resistance to electric current in conductors [duplicate]

Why does the resistance to electric current increases in a conductor when the temperature is increased?
59 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 ...
48 views

Creating some sort of optical transistor

Is there a way to create an optical transistor that runs using a cheap laser and made using mirrors and lenses? My point of using that is to make an optical logic gates, but there is another problem ...
63 views

What are the correct current directions? [closed]

i have a problem in my text book asking me to find the equivalent resistance of this circuit : so i used kirchhoff's first law and drew some abitritary current directions : the two 6 ohm resistors ...
41 views

How much is the phase difference between current and voltage in RC circuit?

In a purely capacitive circuit it is $\pi/2$. But in a RC circuit $$V=v \sin \omega t(1-e^{-t/RC})$$ while $$I=i \sin\omega t (e^{-t/RC}).$$ For such a function how to calculate phase difference?
22 views

Solar cell: Surprising change in EL for varying PEDOT:PSS-thicknesses

I am currently working on improving a solar cell, which is partly transparent and therefore utilizes two transparent electrodes (TCO on top and PEDOT:PSS on the bottom). As PEDOT:PSS alone is not ...
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 ...
58 views

Do noise-cancelling headphones make a lot of unheard noise?

The way noise cancelling headphones work is by listening to sound, and created the inverted sound to 'cancel it out'. Doesn't this mean that the headphones create double the amount of noise, but our ...
86 views

How can I calculate the equivalent resistance of this circuit with resistors in parallel with wires? [closed]

Problem: Calculate the equivalent resistance, $R_\text{eq} ,$ of this circuit: $\hspace{50px}$. My solution attempt Тhe $12 \, \Omega$ resistor and the $6\, \Omega$ resistor are in parallel, ...
38 views

can there be a circuit that changes its input source after a certain limit of voltage is hit? [closed]

I have only recently started learning about circuit components and only know about common components such as a capacitor and a little about diodes, so excuse if im not able to understand common terms ...
16 views

How to synchronize a pulse from function generator and an external pulse

I am currently trying to sync two pulses. One is from a function generator(5V, 1MHz) and the other is from femtosecond laser(which is 76MHz). The femtosecond laser has a {38MHz, 2V} pulse thats in ...
45 views

Strange electromagnetic phenomena

Well, I have some doubts about two electromagnetic phenomena that may be related so I wanted to ask you if you could explain them to me. The first one happend some days ago: I was about to go to bed,...
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 ...
14 views

Why doesn’t the focussing anode diverge the electron beam again?

Consider this diagram of a focusing anode in a CRT: Question: Why does the electron beam not diverge again when it enters the focussing anode (or accelerating anode) while leaving the pre-...
48 views

Distance $E_F-E_i$ in a compensated semiconductor

Given two energy level diagrams for a compensated conductor: At $0~\text{K}$ At $500~\text{K}$ I want to determine for which diagram is the Fermi level closest/farthest from $E_i$. It's a ...
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 ...
52 views

Will high voltage but low current glow a bulb?

Suppose I increase the voltage supplied to a building from a constant power source substantially by putting a transformer. Doing this would reduce the current substantially as well. So will the ...
23 views

Why cant a wire emit light if we apply high enough electric frequency to it? [duplicate]

From my understanding of physics radio and light is the same but with different frequency. Why then there is no lightsource yet made of just a wire and high frequency generator?
26 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 ...
45 views

Electron gun design

I have a question about electron guns. I have read a lot, and all designs use high NEGATIVE voltage ($-1000$ V for example). Is possible to use high POSITIVE voltage like this drawing? Or do you think ...
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 ...
31 views

How does the stud finder work?

My textbook explains how a type of stud finder works by an illustration. What I can’t understand is how does the piece of wood have an effect on the capacitance of the plates when it is so far away ...
33 views

Lagrangian Mechanics to solve arbitrary maximization problem

I've been thinking for some time about how to better find the optimal weights for neural networks and it struck me that when solving Lagrangian mechanics problem you are optimizing the action function....
38 views

Electronics and junctions

In a p-n junction, is it only the electrons that move from the n-type part to the p-type part in order to create a depletion region or is it the movement of both electrons and holes from the n-type ...