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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Good braking system for a mini car that can be triggered by a beam above the car that it will go past

I want to create a braking system for a mini car (essentially an aluminium body around 30cm long with 2 sets of axles with wheels (laser cut circles) connected to the end of each axle on the front and ...
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Electric circuits [closed]

I am having a trouble solving this question about Diodes and voltages, the thing is I have the following circuit that is shown in the image and I know that the input voltage Vi can be described using ...
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Why bridge rectifier circuit is widely used to make power supply? [migrated]

Why bridge rectifier circuit is widely used to make power supply?. which is better, bridge rectifier with capacitor or without capacitor?
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What can I give as an example for a dumb instrumentation system? [closed]

I've searched through many websites and textbooks but none of them have given an example for a dumb instrumentation device.
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Why are most solar panel rated at 12 volts or 24 volts? [closed]

Most solar panel come in 12 volts or 24 volts, why?
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2 votes
2 answers
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I’m trying to charge a capacitor. Would a bridge rectifier charge it like a battery would?

Since a bridge rectifier converts ac to dc. Will this charge my capacitor to max capacity how hooking it up to a battery would? The positive is charging the anode, while the cathode is grounded. Any ...
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2 votes
1 answer
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Questions regarding physical electronics [closed]

I ran into some questions while studying physical electronics. My textbook/lecture note says "An electric field applied to a semiconductor will produce a force on electrons and holes so that ...
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Fluctuative current and voltage graph shown by LabQuest 2

I was in physics class and was tasked to measure current and voltage of a circuit using LabQuest 2. The circuit was connected to a battery, which means it's a DC circuit. But when I use the LabQuest ...
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Why there is no current when diode ia reversed biased?

I try to understand why, really, there is no current (except for leakage) when a diode is reverse-biased. I studied several texts, and noone really explains, like for instance this otherwise very ...
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How is ballistic transport detected/measured experimentally?

That is, measuring the current and calculating the resistance for conducting materials of extremely small size and short paths(such as nanowires for example). How is this done in a laboratory?
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Is this actually a Group II, Group IV transistor? What should its properties be?

This question is for more than a theory. I would like to disprove that what I'm working on is not a Group II, Group IV transistor. I know they CAN exist. I don't know why they don't exist or what ...
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In a series DC circuit, how can one show that the current at each point is same mathematically?

This question has been asked more than ten times in this site before, but almost all of the links I Found are based on informal intuitive argument. In this post, I am asking if it is possible to show ...
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1 answer
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How does putting a resistor change potential difference between two points?

Suppose that we have a closed circuit that consists of a single wire. If we said that the wire has resistance $R_1$, then the electrons would travel through the wire and the potential difference ...
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1 answer
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Uncertainty of output current in voltage-current converter

I have a problem comprehending some things about uncertainty in electrical measurements. Here is illustrative example from my textbook. We use voltage-current converter for measurement. U1 = 10V, I2 =...
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Conceptual doubt about voltage drop in a diode

In the given circuit, I am not sure how to solve it, I know that due to the current the diode is in reverse bias, hence no current should flow through it, But the answer is not given that and a finite ...
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How and why does a nonlinear element produce the sum and difference of two radio frequencies?

For a resonant circuit the voltages of the capacitive and inductance reactance cancel and the currents of the capacitive and inductance reactance also cancel leading to a zero reactance. Is there a ...
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2 votes
3 answers
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Lamp specifications

So when a lamp has a specification of 24 V, 5.0 W, does it mean that it requires at least 5.0 W to work? Can it still consume more power? Or would it then fail? If for example a power supply has ...
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7 answers
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How do headphones and earphones produce good bass if tiny speakers can't produce low frequency sounds very well?

It's a well known fact that small/tiny speakers cannot produce low frequency sounds very well. Conversely, large speakers cannot produce high frequency sounds very well. Hence the need for tweeters ...
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Are electrons quantum confined in two-dimensional semiconductor materials?

In the case of superlattice devices, such as HEMT, the carriers are confined to a two-dimensional quantum well and form what we call 2DEG. Hence, when calculating the carrier density, we need to ...
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Rigorous book (or other materials) on Circuits, Electronics etc

What I usually find in a typical book on these topics is the following structure: "Here is the theorem/fact/formula, here is an example - now go ahead and apply this to some trivial problems that ...
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Why there is no current when diode is reverse biased?

If we can see movement of hole as electron electron moving in opposite direction then why there is no current when a diode is reverse biased.
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1 vote
2 answers
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What is a realistic value for the internal resistance of an ammeter?

As I understand, ideally an ammeter will have zero resistance as it is connected in series with the circuit and so there will be no potential difference across the device. However, in reality there ...
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How do electrons flow in a "random single wire antenna" of a Raspberry Pi, which is DC and just have one path? (no gnd)

I have been amazed by the fact that just by inserting a cable in a GPIO of the raspberry pic acts like an antenna, as far as I know, electromagnetic waves are generated when there's current, and also, ...
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Ultra-Low Temperature semiconductors

What benefits does cooling semiconductors have for technology or any other innovations? I understand semiconductors can become good conductors at high temperatures which are ideal for everyday things ...
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2 votes
4 answers
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Do electrical appliances reduce the heating bill?

When you use an electrical appliance, most of the electricity used is turned into heat. Will the energy cost of using something like an iron be subtracted from the heating bill making it effectively ...
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What vacuum is kept in gen-2 image intensifier night vision devices?

MCPs usually require a vacuum lower than 5e-6 Torr to prevent dielectric breakdown. It seems implausible that small image-intensifier tubes could maintain this level of vacuum for an extended period ...
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Cathode ray tube tungsten filament design?

I am working on building a home cathode ray tube. I'm at the stage of considering the electrical design and filament. From my reading, I've seen that tungsten filaments are a popular choice for ...
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How long can an industrial generator continue producing power?

I asked this same question over in ElectricalEngineering, and the answers were...less than helpful, let's just say. Plus it got closed for being off-topic. I'm hoping that both of those are resolved ...
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How come do resistors lower the current of the whole circuit but the current is the same before and after a resistor? [duplicate]

Thats what I understood from articles on the internet. I just cant wrap my head around it, can someone explain it to me?
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Using ham radio to communicate with an underground crew [closed]

In "Stranger things 3" Dustin uses a ham radio named Cerebro (an image https://www.reddit.com/r/StrangerThings/comments/fhrdml/will_cerebro_make_an_appearance_in_st4/) stationed on a hill ...
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Does the resistance of a filament lamp change?

Recently in a work book there has been a question to explain with the aid of a circuit diagram the method a student could use to investigate how the resistance of a single lamp changes with potential ...
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Removing $1/f$ noise with lock-in-amplifiers

On the Wikipedia page for 1/f noise (at the bottom of the page) it suggests the noise can be reduced if the signal of interest is at DC. DC signals suffer from significant 1/f noise, so one method of ...
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Is there anything other than Resistance, Capacitance, Inductance in a circuit? [closed]

Resistance, Capacitance and Inductance measure certain electrical property of some matter. These term have even given rise to objects like resistors, capacitors and inductors respectively. Few ...
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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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What dictates the built-in voltage of a p-i-n diode?

From what I understood about p-n diodes, built-in voltage is a result of charge difference between p- and n- doped part of a diode. If I increase the cause (doping contrast) of a p-i-n diode, does it ...
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Depletion width of Schottky diode

I'm trying to find the resistance of a Schottky (metal-semiconductor) diode where the semiconductor is N-doped. On the surface this seemed simple, I just had to find the depletion width $w$ and the ...
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Calculating speed of an $N$-channel Junction Field Effect Transistor (JFET)

Hello there I am trying to calculate how fast an $N$-channel JFET (Junction Field Effect Transistor) operates in GHz given that the Gate impedance is $50\Omega$ and Drain-Source voltage is $V_{DS}=2V$....
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What's the difference between Debye length and electrons diffusion length in a n-type semiconductor?

I was reading a book about semiconductor physics and I came across this doubt about the diffusion of majority carriers. The problem was that of a (compensated) n-type doped sample where some radiation ...
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21 votes
7 answers
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Is the voltage ever undefined?

I was in a question in Electronics SE, and a lot of people said something that I'm sure is wrong. They said, "The voltage between two points that are not part of the same circuit is undefined&...
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Three Layer PN Junction

I am dealing with a PN junction which consists of these 3 layers: An N-doped region with $N_D=5\times10^{18}cm^{-3}$ A lightly P-doped region with $N_{Al}=1\times10^{15}cm^{-3}$ with a thickness of $2\...
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14 votes
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Are neurons more energy efficient than transistors?

In terms of order of magnitude, how does a the energy consumption of a typical mammalian neuron (in the brain) compare with the state of the art MOSFET?
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3 votes
1 answer
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What oscilloscope spec to use?

I want to measure a pulse signal using an oscilloscope. The expected rising edge of the signal is in the 1 to 5 ns scale. I have a 20 MHz oscilliscope. Is it correct that the rising edge of the ...
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6 votes
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Radio receivers and the loss of electrons

I'm reading Kenn Amdahls book "There are no electrons" to familiarise my self with the magical world of electricity. Despite Mr. Ahmdahls insistence on the non-existence of electrons, I find ...
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1 vote
1 answer
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How do electrons absorb energy?

I'm trying to understand how lamps work. I have read that the way this happens is when voltage is applied. The free electrons move due to the electromotive force (EMF), and when they collide with the ...
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1 vote
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Electrical model of a tunnel junction: resistor in parallel or series with capacitor?

I would like to understand the electrical model for a tunnel junction (used in a single-electron transistor, for instance). In this lecture, it is said that it can be modelled with a resistor and a ...
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Why does the diode in this AC circuit activate when $u1(t)$ reaches specifically 3.5V? [closed]

In this circuit I am supposed to create the graph for u2(t) where u1(t)=5*sin(314t) V. I understand how to get the amplitude of u2(t) and that u2(t) equals the voltage over the 100 ohm resistor when ...
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Over what distance might this device be able to interfere with car radios?

I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
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What does the characteristic temperature T0 in Variable Range Hopping (VRH) mean?

In Variable Range Hopping, the conductivity could be expressed as σ=σ0exp[-(T0/T)p] where T0 is the characteristic temperature. What is its physical meaning?
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2 votes
1 answer
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What's difference between Watt Electric ($\rm We$) and Watt ($\rm W)$?

So, I'm learning about Radioisotope Thermoelectric Generator (RTG), and wherever I read about it (in websites, in textbook [Fundamentals of Nuclear Science and Engineering]), the unit used for its ...
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1 vote
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Is it really true that radios work better in mountaneous region than in cities?

I was recently travelling somwhere with my family. During the journey we had to pass through a mountaneous terrain. My mother suddenly switched on the radio of car and it was so clear. Is this true ...
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