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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Confusion regarding the quasi neutrality approximation for PN Junction analysis

Why are they called quasi neutral and not exactly neutral? What happens which make them that? In the analysis we have done to derive the I-V characteristics , we always maintained neutrality where ...
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What is equation output voltage in oscillator? [migrated]

I was reading about oscillator circuits but could not find any equation of output voltage in terms of circuit parameters (like mutual inductance, inductance, capacitance, DC sources etc)over internet. ...
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Can we use the photochromic lens as a MOSFET?

So the way a MOSFET works is it has a channel through which either hole or electron current is controlled through the gate voltage making it a switch. Now a photochromic lens has changeable ...
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30 views

Voltage amplifier transistor [closed]

Can we make a voltage amplifier by a simple transistor circuit? The voltage gain of this voltage amplifier wil depend on the resistance we put between the Vout- and the Vout+ terminal . And the ...
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How do you calculate the reflectivity of material from its conductivity?

How do you calculate the reflectivity of material from its conductivity? For example, gold at v=9x10^12/s (this problem is from the electronic property of material by Hummel). Is it possible to use '...
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1answer
22 views

Is “quaternary” adjective redundant while speaking of InGaAsP?

I'm reading an article. One sentence looks as following: The 500 nm thick waveguide layer consists of an InGaAsP quaternary layer But since InGaAsP is quaternary compound, why do they write ...
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1answer
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p- and n- contact metal difference

I'm reading an article about some electronic components and the authors specify that they used p- and n- contact metals, but without giving details about those metals, or what material are they really....
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5answers
378 views

Why complex numbers are used in electronics? [duplicate]

The impedance of a capacitor or an inductor is imaginary. How do we know these quantities are imaginary?
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Can someone help me decipher the code for the arduino? I am totally lost [migrated]

The code is as follows: void loop(){ light = analogRead(5); Serial.println(light); analogWrite(3,light/4); }
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1answer
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How can a doped piece of silicon (with different concentration) still be intrinsic? [closed]

I am trying to solve a question which says: A piece of silicon is doped with Nd = 1.8*10^(13) and Na= 3.8*10^(13) Prove it is intrinsic at 500k. I don't know how is it possible for silicon to be ...
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1answer
38 views

Does aluminum in between stop induction cooktop from warming iron?

There is an ongoing discussion about induction cooktops on Seasoned Advice. The situation in nutshell is: About 1 cm of aluminum on the cooktop. About 1 cm of iron on top of the aluminum. My ...
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1answer
53 views

Why a photon cannot change the crystal momentum of an electron?

We know that absorption of a photon excites an electron from the valence band to the conduction band without changing its crystal momentum $\vec{k}$. Why can't a photon change the crystal momentum of ...
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1answer
48 views

Derivation on the effect of temperature on Fermi distribution function [closed]

With reference to Section 10.7 Effect of Temperature on Fermi Distribution Function from the text Solid State Physics, 2nd ed., M. A. Wahab, the last two equations are given like this: $E_{F_0}^{3/2} ...
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What is the maximum negative output voltage of an emitter follower with a split +10v/-10v supply? [migrated]

I'm perplexed by a passage in Horowitz and Hill's "Art of Electronics" (1st ed., p. 54). They present the reader with a simple emitter follower circuit. The input voltage is a 10v amplitude sine-...
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28 views

Physics behind impedance matching and reflection

I have been looking for cause of signal reflections in transmission lines everywhere it is concluded that the reason is impedance mismatch. I understand that if the impedance changes in the path of ...
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1answer
26 views

RLC Bandpass Filter network

Can anybody tell me what the "s" in this equation is? I am looking for the transfer function of this circuit
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27 views

Can an extrinsic semiconductor have a positive temperature coefficient?

My professor says in his notes that, because electron mobility decreases when temperature increases high enough, the conductivity of an extrinsic semiconductor actually decreases at such temperatures. ...
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17 views

Emitter current doubt

In my semiconductor lesson about npn transistor I found emitter current (Ie)=base current(Ib)+collector current(Ic).Now for practical purpose we can get the values of different current using micro and ...
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1answer
22 views

Signal demodulation in a frequency mixer

Let's assume we have a signal $f(t)=A\sin(\omega t)+B\cos{\omega t}$. In order to isolate the '$A$-part', the signal is mixed with an oscillator signal $g(t)=\sin(\omega t)$ generating a constant ...
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1answer
65 views

How do semiconductor devices break when hot? [closed]

When a diode gets too hot it may start to conduct in both directions, and it may remain this way even after cooled down. What happens in this process? I found some answers that suggest melting. ...
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3answers
88 views

$V$-$I$ characteristic of a solar cell

please explain the VI characteristics of a solar cell. The characteristics is given in my book without any explanation. How can the Voltage decrease on increasing current shouldn't it be opposite. ...
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1answer
69 views

Passive dissipator block between two peltier cells seemingly raising overall temperature differential

I am experimenting with stacked Peltier cells trying to build a simple diffusion cloud chamber. I noticed that when simply stacking two peltier cells the upper side reaches a temperature (around -15 C)...
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59 views

Why don't cell phones pick up music in phone calls? [duplicate]

Why is it that a listener on a cell phone cannot hear music on the other end? For example, the source phone is located either in a car with music being played, or is at a concert. The listener hears ...
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1answer
161 views

Noise cancelling speakers to cancel sound in the room [duplicate]

A thought of mine from class, where not everyone is the "silent kid" type. The teacher would very often need to shout to keep the class barely quiet enough for the students who actually are paying ...
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0answers
13 views

What happens to an insulating barrier in a semiconductor nanowire during thermal fluctuations?

I was wondering about semiconductor nanowires with a barrier during thermal fluctuations. Could anybody explain or account for why (or refer me to an article that does), when running a current ...
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1answer
88 views

Drift velocity component of electrons in alternating current

I'm not sure if this question will qualify as cross-posting, but feel free to tell me if it does so that I can delete it. However, this question certainly does relate to both physics and electronics, ...
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2answers
79 views

Is the EMP threat to the power grid supported by physics? [closed]

Every once in a while I come across some article saying that our modern power grid could be knocked out of commission for up to a year by an electromagnetic pulse. I'm skeptical of such warnings. ...
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1answer
68 views

Why mobile phone and laptop computers’ screens are polarized?

Why is it necessary to use either a linear or a circular polariser for mobile phone and laptop computers’ screen?
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1answer
23 views

Is there any factors depends for electromagnetic waves?

I am staying in hostel. One person said me that he is getting better connection with the wifi when the door is opened. I am wondering that what an electromagnetic wave can do with the door? Is there ...
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1answer
23 views

MOSFET Mobility

The surface mobility is lower than the bulk mobility because of surface roughness scattering What is surface roughness scattering? How does it affect the mobility?
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How is resonance isolated from other parts of a system

I am looking for a qualitative answer, if possible - that is an interpretation of the laws and corresponding mathematics, since neither of these is relevant to my area - but the overall trends/broad ...
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2answers
70 views

Doesn't a commmon emitter amplifier violate law of conservation of energy?

Basically voltage and current is gained in an amplifier which ultimately results in power and energy gain? Where does the energy come from? Does it violate law of conservation of energy?
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2answers
104 views

Why is the power unchanged by a transformer?

If we have a step up transformer then the voltage at the secondary side will be more than the voltage at the primary side. Since we all know that POWER = VOLTAGE * CURRENT and because voltage at the ...
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2answers
27 views

Why does increasing capacitor dielectric allow it to store more charge under constant voltage?

Take two capacitors that are each connected to and charged from identical constant voltage sources. The capacitors are identical in every way (distance, area, etc) except that their dielectric ...
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0answers
48 views

Why does this magnetic charger cause short circuit when it sticks to the metal leg of my table? [closed]

Recently, I have bought this product. It is basically a USB cable, with a magnetic end, and a tiny attachment that goes into the mobile device. I plugged it into my laptop cooling stand (which has ...
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0answers
40 views

How does a transistor work in an electric circuit?

For example, if this is the circuit containing the transistor: The positive holes move to the right hand plate of the collector. The electrons must be moving in the opposite direction from the wire ...
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1answer
19 views

P-I-V laser diode characterization: Integrated sphere or not?

I read that to do a P-I-V laser diode characterization there are two ways: -Coupling the laser to the Detector through an Integrating Sphere. Setup would be: laser diode-integrated sphere-...
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1answer
180 views

What is the source of high pitch noise made by Polaroid instant cameras?

I've been wondering for a long time now, what is the source of that faint high pitch noise that is made by old Polaroid instant cameras. For the reference, the sound at 0:24-0:30 in this video. I ...
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42 views

Hetero junction - similar work-functions

Why is it important that the two semiconductors in a hetero-junction, that is brought into contact, have similar work-functions? (If it is important). Obviously it's important for a metal-...
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1answer
41 views

Using capacitors for rectification

In my textbook it states that: To decrease the size of the ripple and make the DC even more constant we can: use a larger capacitor use a load that draws a smaller current (has a high resistance). ...
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1answer
30 views

Floating Voltage Referenced to Ground [closed]

So, I came across something interesting today at work that is completely confusing me. We have floating 130V battery backups, and I am told there is neither any ground reference, nor any center tap on ...
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2answers
46 views

What Temperature Will Electrons Escape Quantum Wells?

I'm watching this video to understand quantum tunneling (Infinite Barrier/Particle in a Box model). The speaker says that electrons will most likely not gain the energy to escape a quantum well at ...
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1answer
53 views

Small speaker with full frequency range? [closed]

As I understand Hi-Fi headphones are usually small in diameter and support full range like from 20 to 20 000 Hz. But when I try to buy small loudspeaker I see that they do not support low frequencies ...
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1answer
125 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. ...
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14 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 ...
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3answers
49 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 ...
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1answer
18 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?
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3answers
63 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 ...
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1answer
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 $t = t_1$, ...
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1answer
43 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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