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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If a transistor only gives you a maximum Current flow, what's the maximum voltage? [migrated]

You see, in some data sheets of npn transistors it only says "maximum Collector - Emitter Current". But my question at what voltage ist this current value given, because 1amp at 1 volt is somehow less ...
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31 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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1answer
17 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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22 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
111 views

Why is the emitter current of a common emitter slightly greater than the collector current?

I'm trying understand where electricians came to agreement that Ie = Ib + Ic. I know that the base of a NPN transistor is very thin, allowing electrons to flow through to the collector which explains ...
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1answer
160 views

Patch antenna excitation

How can we excite the patch antenna in different modes like TM10 and TM30? If a microstrip patch antenna resonates at TM10 mode can it resonate in other modes also like TM30?
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5answers
22k views

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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0answers
22 views

What are some electrical engineering related experimental projects suitable for second year undergraduate students? [closed]

I am a high school student in the final year and I need to do a large, complex physics project, which entails an experiment. For reference,I am looking for a complex project on the level of a second ...
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2answers
93 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 ...
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16 views

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
66 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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69 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
25 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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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
36 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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0answers
8 views

Why is grounding required in a transistor circuit? [migrated]

This picture is given in my textbook regarding a n-p-n transistor circuit: Why is the emitter grounded? Why can’t it directly and only connected to the negative terminal of Vcc?
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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
68 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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2answers
437 views

What are the wavelengths of the red, green, and blue lights used for making LED pixels?

LED screens in televisions and smartphones use pixels that use a combination of Red, Green, and Blue diodes that can produce any color when used in the correct proportion of intensity. My question is,...
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1answer
179 views

Output in a half wave rectifier

In a half wave rectifier only a single diode is present. One end of the secondary wire of the transformer is connected to the p side of diode while the other to the load resistor. The n side is ...
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0answers
38 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
317 views

About The foxhole radio: coil rotation times, whether capacitor's needed

I recently tried to make a DIY foxhole radio. Althogh I made it according to the manual (140times coil rotated, ground(220V), blued razor blade, pencil core and antenna (just a steel stick about 1 ...
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3answers
2k views

Use of slip rings and its working in a AC generator

What is the use of slip rings in an AC generator and its working? What would happen if there was no slip rings?
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1answer
33 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
378 views

How can depletion region be formed at the center?

Let's consider an electron at the junction in the n-type region. As it moves into the p-type we say it leaves behind a positive ion and hence in this way electrons at the junction in the n-type create ...
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1answer
28 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
43 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
51 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
180 views

Internal resistance and a resistor as a potential divider

Based on the fact that batteries have some kind of internal resistance, if I had a circuit that consisted of a battery and a resistor of some kind would they act like a potential (voltage) divider? ...
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1answer
162 views

Accelerometer readings

Good Night. I have a implemented a accelerometer, a gyro and a Magnetometer in raspberry pi. I want measure the linear acceleration (acceleration without gravity) but i don't know how to do it or if ...
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1answer
112 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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0answers
12 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
40 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
17 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
60 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
30 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/...
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1answer
161 views

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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1answer
61 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 ...
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2answers
76 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 ...
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0answers
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 ...
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3answers
26 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 ...
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1answer
445 views

Why is voltage gain highest in common base transistors whereas lowest in common collector transistors?

Although the common base transistors have current gain lowest and the common collector transistors have current gain highest.
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1answer
19 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?
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34 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-...
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0answers
16 views

Noise Fundamentals - Johnson Noise

How can be Johnson Noise measured with the help of single electronic instrument (experimentally)?
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2answers
32 views

Johnson Noise experimental measurement

How can we experimentally find out value (extent) of Johnson Noise of any resistor with certain bandwidth and teperature?
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1answer
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 ...
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2answers
51 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 ...
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1answer
17 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?