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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474 views

Why a tunnel diode (TD) is called a diode?

Traditionally, a diode is a 2-terminal device that limits current to flow in one direction, i.e. a rectifier. But a "tunnel diode", according to wikipedia, is not rectifying: In the tunnel diode, ...
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2answers
9k views

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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2answers
453 views

Is it possible to record the 'blue air" effect when a core goes critical?

I've been studying about radiation, and I saw something called the Demon Core. Apparently, it was a core that was under experimentation by the government in Los Alamos to see the exact point at which ...
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1answer
47 views

How does a staircase switch work? [closed]

Well, I live in a descent old kind of house with old wiring and connections but a fascinating thing in my house is a 2 way switch (I don't even know if it is called so). The arrangement is like we ...
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2answers
28 views

Can someone explain me the following line: “The RC circuit averages past history at the input with a weighting factor of e−Δt/RC.”

"The RC circuit averages past history at the input with a weighting factor of e−Δt/RC."
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1answer
53 views

Does the shifting of the Fermi energy level of an intrinsic semiconductor mean that $n \neq p$?

It has been stressed out in the books that I've consulted that, for an intrinsic semiconductor, $n=p$. However, with this in mind, they also derivate the following equation: $$E_{F_i}=\frac{E_c+E_v}{...
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4answers
1k views

what could generate a high-pitched whine in electronics where the frequency depends on the current?

So I was operating a Laue machine recently which generates x-rays and fires them at a sample, and I noticed that there was a high-pitched whine coming from the instrument (nothing abnormal, just ...
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2answers
89 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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4answers
215 views

What makes quartz oscillators vibrate?

I understand that the principle behind it is piezoelectricity and electrostriction (inverse piezoelectricity), but how does one make the crystal vibrate? The only thing I can think of is using an ...
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1answer
858 views

Larsen effect and pitch of sound

Why Larsen effect produces always high pitched sounds, never low pitched?
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1answer
222 views

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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1answer
2k views

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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2k views

Can we “use” a capacitor while simultaneously charging it?

I know that capacitors can be charged to work like a battery . But I wanted to know whether we can charge a capacitor while it is in use ( given that the current supplied to it is more than what it ...
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1answer
207 views

Why Microchannel Plates can be operated only in vacuum?

Why it is said that the Microchannel Plates can be operated in vacuum? What is the maximum pressure in which it can be operated? Also, while it is not operating, should it be kept in vacuum? Is this ...
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4answers
10k views

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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2answers
4k views

What is the difference of the two stable states of a Flip-flop?

In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information. [...] Flip-flops and latches are used as data storage elements. Such data ...
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3answers
58 views

By what mechanism does a solar flare overload electronics?

I apologize for my ignorance, but I lack the underlying knowledge to meaningfully research this myself. My knowledge of both Solar Flares and EMPs comes almost exclusively from pop-sci reading. I've ...
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1answer
117 views

Why are the active noise cancellation headphones subjectively better in reducing “periodic” noise?

According to experience of mine and of my friends using active noise cancellation headphones, the technology is much more efficient in reducing "periodic" noise, such as humming of jet engine, fridge ...
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2answers
296 views

Science of Daisy-chaining [closed]

As everyone knows daisy-chaining power strips is very bad and dangerous. But could someone tell me why it's dangerous from a physics standpoint? (i.e. its effect on voltage, current, etc)
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1answer
58 views

What happen to organic solar cell when applied electric field? [closed]

For example, I have a PTB7:PCBM organic solar cell. I applied electric field in forward basis. Will it contribute to increase charge separation? Then, if I do in reverse basis, what will happen to ...
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2answers
223 views

Why don't radio waves ruin electronics?

Out of curiosity, I estimated the voltage amplitude for typical visible light. Wikipedia says that sunlight hits the earth at about $1000 W / m^2$. The intensity of an electric field is given by $$I =...
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1answer
319 views

What happens if a PMT (photmultiplier tube) is run below its operating voltage?

I have this Hamamatsu PMT that says its operating voltage is 1500 V. However, it has serious electronic/background noise at LLD=0 at that operating voltage. If I lower it down to about 1.02 KV, noise ...
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1answer
428 views

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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4answers
1k views

What is the potential difference across a disconnected diode? [duplicate]

I think potential difference across disconnected diode should be zero but how? the last graph tells that there is a potential difference between the two ends of a diode. then how can be it zero?
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1answer
134 views

Equivalent DC circuit with charged conductors

I am trying to find equivalent circuit for a circuit composed of interconnected capacitors when isolated pieces of conductor may carry nonzero electric charge, and I have been struggling with this ...
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1answer
336 views

Why does a field-effect transistor (FET) with wrap-around gate work at all?

In the recent years several publications have presented field-effect transistors (FETs) that are based on semiconductor nanowires with a gate electrode that is wrapped around the whole nanowire ...
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2answers
695 views

Problems in the modern semiconductor/electronics technology?

From what I have read, the problem with modern semiconductors/electronics seems to be quantum tunnelling and heat. The root of these problems is the size of the devices. The electrons are leaking out, ...
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1answer
67 views

Why are there no brushless motors with more than 3 phases (6, 9, etc.)?

My understanding is that adding phases will (up to a point) add the ability to push more power through a motor (more Amps total, same per individual winding wire), generating more torque for similar ...
2
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1answer
183 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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1answer
44 views

Unknown pulses from SiPM without any source or detector?

I have a SiPM set up with its PCB, no amplification at all, reading out to an oscilloscope. If I supply 29.8 V, which is the maximum power (with overvoltage), I get some random peaks on the ...
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1answer
2k views

Why do lower frequency need more cone excursion?

I am not 100% sure about this,but my current understand of loudspeaker is that moving coil woofer with certain fixed value surface area playing 1000 Hz frequency at 100 dB spl will be moving back and ...
2
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1answer
89 views

What is the difference between Si pixel and Si strips used in CMS Inner tracker at CERN?

What is the difference between Si pixel and Si strips used in CMS at CERN? Both are used for tracking and as the CERN website mentions, they are also based on the same working principles. Or are they ...
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1answer
152 views

Accumulation Region of an NMOS

I'm trying to get a better understanding of how the NMOS works when a negative voltage is applied to the gate. So I currently understand that the $P^-$ substrate is lightly doped with such a ...
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1answer
61 views

Won't the Power be dissipated in the first quadrant of this graph?

In the following picture: In the first quadrant of the V-I graph(for an Independent Current Source, where the voltage supplied is positive on the top) won't the power be dissipated instead of being ...
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1answer
4k views

The width of the space charge region in a pn-junction

Given a pn-junction as in the picture below. Which quantity determines the width of the space charge region? Or in other words, why don't the electrons in the n-doped region wander towards the ...
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2answers
4k views

Why is $I$-$V$ characteristics of a solar cell drawn in the 4th quadrant?

My book says because a solar cell does not draw current but supplies it to the load. I don't quite get the explanation. How is it related?
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1answer
879 views

Why does small change in Base current causes a larger change in collector current in case of transistors? [closed]

Why does small change in the base current causes larger change in the collector current. That is say if I increase the base current buy a small amount why the collector current increases by a very ...
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1answer
56 views

Effect of charge on electric circuit in free space

Assume I put some electronic device, a laptop for example, in free space. Now add electrons to the object. It will become progressively more negatively charged. At what point will the laptop (or ...
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1answer
227 views

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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2answers
397 views

Shining light (of a particular frequency) on an insulator to make it into a conductor

Recently I read about band theory of solids. The energy difference between valence band and conduction band determines the conductive property of solids. Suppose I take an insulator and shine it with ...
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2answers
96 views

Why are holes (in a semi conductor) regarded as particle?

Can I say that holes in a semiconductors are treated as current-carrying conventional direction ?
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1answer
4k views

Calculating Boltzmann constant using semiconductor

My task from the latest laboratory exercise in physics is to calculate Boltzmann constant from known temperature, current and voltage. We were given this circuit: By changing the resistor value, I ...
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2answers
291 views

What will be the effect of placing a light source very close to a photodiode?

What will be the effect of placing a photodiode really close to a laser source and what should be the appropriate distance between a light source and photodiode to get maximum output current?
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1answer
3k views

Calculate TEC efficiency

I am currently doing a small experiment using a Peltier to cool 250ml of water. My aim is to achieve the cooling of 250ml from 23degC to 8degC in under 20minuets which I have done by strapping the ...
2
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1answer
269 views

What do I get when measuring on top of metal/insulator/metal by kelvin probe?

I am using a macroscopic Kelvin Probe for work function measurement. There's one confusing condition. If I measure a trilayer thin film stack with a structure of ITO(bottom)/PMMA(100-200nm)/Al(top), ...
2
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1answer
4k views

How to understand exciton?

I know that exciton is an electron and hole orbiting around each other(at least that is what I have heard). So if the hole is a hypothetical particle with a plus sign, meaning that it is a lack of an ...
2
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1answer
266 views

How does rust behave as a PN junction?

Reading about old-fangled radios the reference quoted below indicates it was/is possible to use a rusted razor (or perhaps any similar thin corroded metal strip) as a detector. Some resourceful GIs ...
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1answer
1k 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
451 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
54 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 ...

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