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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What's the physical meaning of the imaginary component of impedance?
As you know, impedance is defined as a complex number.
Ideal capacitors:
$$
\frac {1} {j \omega C} \hspace{0.5 pc} \mathrm{or} \hspace{0.5 pc} \frac {1} {sC}
$$
Ideal inductors:
$$
j \omega L \...
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Pn junction voltage drop?
This image from wikipedia, explains that there occurs a potential drop across a pn semiconductor junction, and an electric field confined to the depletion region.
I already know the reason for the ...
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What would be the effective resistance of the ladder of resistors having n steps
I'm a tutor. This is a high school level problem. In high school, every one have might have solved a problem of effective resistance of a ladder of resistors having infinite steps. Now the problem is ...
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Why can't you hear music well over a telephone line?
Why can't you hear music well well over a telephone line?
I was asked this question in an interview for a university study placement and I unfortunately had no idea.
I was given the hint that the ...
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In the diode equation, why the exponential $\exp$ and the ideality factor $n$ are there? What do they represent & what is their significance?
In the Shockley diode equation, why the exponential $\exp$ and the ideality factor $n$ are there? What do they represent & what is their significance?
I have to work on Solar Photovoltaics, and ...
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How does current flow from the emitter, through the base and to the collector in a NPN transistor?
So, I understand that for a NPN transistor to work the emitter-base junction needs to be forward biased and the collector-base junction needs to be reverse biased. I understand how current flows from ...
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Why do circuits work so fast?
Drift velocity (explained to me as how fast the electrons are moving) is really slow. My book says the electrons move at around 10 mm/ s.
If electrons move so slowly how do circuits work so fast? If ...
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Dust patterns inside electronic product - what causes this? [duplicate]
(Note: another similar question from a few years ago yielded nought but speculation. I have at provided some detailed observations in the hope that the community can come up with something rigorous as ...
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Working of a p-n junction diode when forward biased
If p-type semiconductor and n-type semiconductor of a diode are equally doped, and if the diode is forward biased, then holes will move toward the n-type semiconductor and electrons will move toward ...
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What's the purpose of capacitors in parallel
In my school textbook it is written that the capacitor acts as a filter, that is, it decreases the fluctuations in the potential difference across the load.
But since all the components are ...
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What is meant by phase coherence of electrons?
I came across a term "phase coherent electron devices" in the book Condensed Matter Field Theory by Atland and Simons. What is meant my phase coherent electrons (coherence is a term generally talked ...
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What is the role of center-tapping in a full wave rectifier?
Note: I have already tried googling. Although similar questions have been asked on different forums, I couldn't find a detailed explanation, which I could really understand.
Circuit diagram courtesy ...
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Why is 2-terminal sensing less accurate than 4-terminal sensing if the internal resistance of leads is known?
I have a pretty good understanding of 2-terminal vs. 4-terminal (kelvin) sensing measurements. I understand that in the 4-terminal measurement, current is supplied by 2 terminals that are separate ...
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Why capacitor pass AC and block DC current? [duplicate]
We know that in circuit capacitor block the DC current and pass AC current. My question is how a capacitor block DC and pass AC?
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Why, microscopically, is the voltage drop across a resistor affected by the current through it?
If voltage is a potential difference, describing how much energy will be lost per unit charge as charge carriers pass through the resistor, why would the rate at which charge flows (i.e. current, $=dq/...
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Photomultiplier/ voltage divider troubleshooting
I have a Photonis XP5301 PMT to use for fast neutron detection (detector optically glued to the PMT window). I can't quite figure out why its not producing a spectrum. First of all, I have multiple ...
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Are holes electrons moving in the same direction of the electric field?
Holes are electrons, but with negative mass. That's said, so by applying electric field, electrons (n) move in the opposite direction of the field, while holes (other electrons) move in the same ...
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3
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Small resistance in parallel with with a large resistance. Does it affect the current in the larger resistance?
I'm a stupid high school student trying to understand domestic circuits. I've recently learned about the earth wire which reduces the value of current traveling through a person's body when they touch ...
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Semi conductors (holes and electrons)
The following relation is mentioned in my text book for semiconductors in thermal equilibrium.
$$n_e ×n_h = n_i^2$$
$n_e$ stands for the number of electrons.
$n_h$ stands for the number of holes.
...
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Why do the following Network Transformations give different answers?
I did a Star to Delta Network Transformation and a Delta to Star Network Transformation on different parts of the original circuit as shown in the image below.
It gave me two new circuits. On solving ...
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light point and photosensor
When a laser pointer is pointed at a screen or at a target that spot can be detected because the laser beam falls on the target and bounces back and then is detected by a photosensor.
But, what if it ...
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Saturated BJT Transistors. V CE < V BE : AKA - Things that make you go “Hmmmm”
At the risk of being blasted for cross-posting, I am posting this question again here in the Physics department. It is a duplicate of this post in the EE forum. However, I would like to get some ...
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Is there a physical limit to data transfer rate?
Is there a physical limit to data transfer rate (e.g. for USB $3.0$, this rate can be a few Gbit per second)? I am wondering if there is a physical law giving a fundamental limit to data transfer rate,...
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How is data transferred between devices?
If you send a text from your phone to your friend, do electrons move from your phone to your friend's phone? How is text transferred (physics wise)? I am a programmer and I want to know how it is ...
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How do Zener diodes maintain the potential across their terminals?
My physics book has a topic about Zener diodes being used as voltage regulators in the reverse bias.
Well, I'm curious to know how does a Zener diode maintain the potential across its terminals after ...
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Why does it spark when I push a plug in the electrical socket?
When I slowly push a plug into the electrical socket I can often see sparks. Can anybody explain why? Can this be possibly harmful for the devices I plug in?
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Verifying radiation measurement smart phone applications
I've stumbled upon a strange class of Android applications lately. (And I'm sure such applications are available for other platforms too.)
These apps claim the ability of detecting radiation. The ...
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Current when resistance is 0
A short circuit has $\rm 0$ resistance. We use Ohm's Law $\rm V=IR$. If $\rm R=0$, then $\rm V=0$. Doesn't this mean $\rm I$ can theoretically be anything? Thus $\rm I$ can be like $\rm35A$ for ...
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Main cause of self-charging of unshorted capacitors?
In the lab, we keep all of the high voltage capacitors shorted when not in use, and rightfully so. They tend to spontaneously charge when left for some time and become extremely dangerous. while the ...
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How come a mobile phone signal is blocked by aluminium foil, but Wi-Fi gets through?
Major puzzle for me. I have done a demonstration in lectures for years now, where I show that a mobile phone call can be blocked by wrapping the phone in a single sheet of standard Aluminium kitchen ...
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Could we build a supercomputer out of wires and switches instead of a microchip?
I thought of this question; would too much wiring make a computer burn down? Or can you build an actual full-speed supercomputer computer using switches and wires?
In other words, could simply adding ...
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The role of resistor in e.g. an AND gate
What is the role of the resistor in e.g. an AND gate like this one? :
One often sees lots of resistors in electric circuits, but I haven't really understood their role.
user6511
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Current through the reverse biased junction in transistor [closed]
A transistor is a three terminal device. One terminal is called emitter, one collector and in between them is base. Now, during biasing the junction between emitter and base is made forward biased and ...
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Textbook recommendations for electrical circuits and electronics?
I'm a junior physics major focusing on theoretical physics. I didn't take any courses in electrical circuits or electronics (though I did take E&M).
Recently I started feeling that this is a ...
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Can we prove "Lumped element model" mathematically?
Maybe this question is both in the fields of engineering and physics.
As it seems the electrical quantities like Resistance, Capacitance, Inductance, and so on are quantities we assign to distributed ...
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Memristors: how are memristors modeled in terms of impedance?
How are memristors modeled in terms of impedance?
I have been searching the net for memristors, but could not get much of an idea. I'm not interested in how memristors are made (by combining ...
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Are the $V$ in electronics and the $\phi$ in physics the same?
Is the electric scalar potential $\phi$ in physics the same thing as 'voltage', $V$, in electronics?
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When does Thevenin's theorem not apply (modelling a power source with a ohmic internal resistance)
Most physics text books say that a power source can be modelled as an EMF with a internal resistance. This is also know as Thevenin's theorem or Norton's theorem. However I have read in some sources ...
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Why are there two quasi Fermi levels and only one Equilibrium Fermi level?
I am reading a book and I'm trying to understand the concept of quasi Fermi levels.
For example,
A steady state of Electron Hole pairs are created at the rate of $10^{13}\ \mathrm{cm}^{-3}$ per $\...
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Photomultiplier pulses only at first few channels?
I have an old Hamamatsu PMT, and I have a scintillator that can detect neutrons, gammas, alphas. But no matter what source I use, I'm only seeing counts at the first few channels (up to about the 15th ...
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Confusion on AC in LIVE & NEUTRAL WIRE
So if an AC current means the elctrons are alternating or changing direction in a given time, how does this apply to live & neutral wire, don't they flow in one direction only? Please answer it as ...
user209491
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Spin FET Transistor
Spin FET Transistor.
When a gate voltage is applied to a current of spin polarized electrons, a spin precession will occur. If this spin precession is enough to make the bulk electron spin ...
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Why some elements of same group cannot be used for doping semiconductors?
15th group elements like As, Sb, P can be used for doping whereas N and Bi cannot be used for doping even though they too belong belong to 15th group. Why?
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Non-ohmic conductors
Non ohmic conductors are said to be the conductors that do not obey Ohm's Law. The V-I graph for them is not a straight line unlike ideal ohmic conductors.
According to me Ohm's Law states:
The ...
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Current contribution in a p–n diode under equilibrium
We say that under equilibrium, no further movement of majority carriers takes place due to the immobile ions or the electric field or built in potential stops it.
But in many cases and videos I seen, ...
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Shifting of Energy levels in PN junction under Equilibrium
My question is during equilibrium is achieved under no biasing, why it is that in fermi level diagram representation fermi levels are raised in p type nd lowered in n type. Is it not possible we ...
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Inductor back emf
If I have that circuit, the equation that describe the circuit is: $\epsilon = L \frac{dI}{dt}$.
Now, if the back e.m.f. is equal to the source e.m.f, how current can pass? and it should pass because ...
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Dynamic resistance of diodes and the depletion zone
According to Resnick, Walker & Halliday's Fundamentals of Physics (10th edition),
Figure 41-15 shows why a p-n junction operates as a junction
rectifier. In Fig. 41-15a, a battery is connected ...
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Using DC voltage in Transformers
I understand that a transformer can step up or step down voltages when it is fed in AC. However, I am wondering why can't we use a non constant DC source as input.
For example, if I rectify the AC ...
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If vacuum is an insulator, then why do charges flow inside a vacuum tube?
Since vacuum or free space is used as insulators in capacitors, how is it possible for charges to flow inside a vacuum tube?
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