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Questions tagged [electrical-engineering]

The engineering discipline concerned with the study, design and application of equipment, devices and systems which use electricity, electronics, and electromagnetism.

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Powerlines in Asian villages are they safe? [closed]

Powerlines in Asia - I have seen lots of lines wound up or passing through bushes. Is this dangerous? How does this work?
Diatom's user avatar
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1 answer
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Will the electrical potential difference between the Windward and Leeward sides of a mountain range generate electrical current?

I would like to know if it is possible that the electrical potential difference between the Windward side and the Leeward side of a mountain range, due to a thunderstorm occurring on the Windward side,...
user57467's user avatar
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2 answers
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Can we catch signals from a cellphone using an external device? [closed]

What if someone stole em waves from our mobile devices to listen to our conversations or get our OTP. Whatever encryptions they have they are just EM waves innit and they cannot be propagated only in ...
Newtron Malayalam's user avatar
1 vote
0 answers
21 views

Calculate optimal spacing of vertical magnetometer configuration in Magnetic Ground Survey

I have a vertical magnetometer configuration, and measure lines on the ground. I want to calculate the optimal spacing, based on the interpolation between the lines. Applying the generalized ...
user387449's user avatar
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Why electric field increase near the cable connected in AC 220V socket even current is zero?

If I put low frequency electric field meter near the connected cable in AC 220V socket, he show 1200 V/m even if device is turn OFF(zero current), if disconnect cable from socket, field drop to 8 V/m. ...
22flower's user avatar
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3 answers
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Why do lamps in circuit have potential difference but two points in cable without anything in the middle of it have no potential difference?

I'm preparing for my EE major, this is my starting point.
Raudana Muntazar's user avatar
1 vote
0 answers
104 views

Deriving the Cable Equation from Maxwell's Equations

My goal is to reach equation 12 on this wikipedia page: Cable Theory. The demonstration is usually done by making an infinitesimal circuit, but I would like to get there via Maxwell's Equations by ...
Ícaro Lorran's user avatar
2 votes
1 answer
123 views

Can aluminum shield magnetic fields?

Say I have built a simple working AC 50 Hz transformer. It has copper coils at each end of a soft iron rod. If I slip an aluminum tube over the soft iron rod, so the copper coils now are over the ...
itsme's user avatar
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1 answer
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Back EMF in electromagnetic coil

I am trying to quantify the back EMF generated while actuating an electromagnetic coil, this would be included in a general calculation to estimate the coil output under a variety of conditions. My ...
Stefano's user avatar
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Is there any electronic devices that maintain charged state?

I want to know how to make electronic devices that are continuously charged to + or - state on which surface when voltage is applied to utilize the dielectric polarization property, or if there are ...
SungJin Park's user avatar
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1 answer
62 views

I don't really get transistors. How do they work exactly in the active region?

So in an NPN transistor, when the base-emitter is forward biased, and the base-collector is reversed biased, electrons from the emitter get to the base. That part I understand, electrons are the main ...
Stojan Zoran's user avatar
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1 answer
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Built-In Potential (Forward vs Thermal Equilibruim)

According to my book the built-in potential $V_{bi}$ for a PN junction under thermal equiliubrium is: $$V_{bi}= \frac{KT}{q}In(\frac{n_{no}p_{po}}{{n_{i}}^2})$$ where $n_{no}$ and $p_{po}$ are the ...
Abe 's user avatar
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2 answers
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Why is potential continuous at dielectric conjunction?

Lets take for an example, a spherical capacitor with two dielectrics. The Electric Field will then be given by $$\frac{Q}{4\pi\varepsilon_0\varepsilon_r r^{2}}$$ We know that then the electric field ...
MJSTX 's user avatar
1 vote
0 answers
26 views

How do I calculate thrust for a high bypass turbofan engine? (7th grade) [closed]

so i'm a 7th grader trying to create something using a high bypass turbofan engine but I need to learn how to calculate the thrust for it and i'm unsure on how I am meant to do that. If anyone has any ...
random dude tryna learn stuff's user avatar
1 vote
1 answer
171 views

Does resistance of a rheostat affect current in the circuit?

This is the typical experimental setup to determine the unknown resistance of a given wire. As we move the sliding contact of the rheostat, we get different values of voltage and current. a plot of V ...
Navya's user avatar
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Charge moving in an electric field and magnetic field? [closed]

lets say I have an electron moving towards an oppositely charged plate. Perpendicular to the electrical force vector, exists a magnetic field. How would I calculate the force on the electron? Like ...
Jais's user avatar
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Resistance in series also slows current down so why is resistance connected in parallel in galvanometer ammeter and not in series?

When we convert a galvanometer into an ammeter we connect the resistance in parallel, the only reason we connect a resistance in parallel with galvanometer is so less current passes and the flow of ...
Mathematition_From_Wallmart's user avatar
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1 answer
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For intrinsic semiconductors, is the gap Energy equals $E_c-E_v$ or $E_c+E_v$?

So I have a problem with the intrinsic Fermi Level because by definition it is in the middle of the gap energy, and knowing that Eg=(Ec-Ev), we should have Ei=(Ec-Ev)/2. But when we follow the ...
anass bakour's user avatar
2 votes
1 answer
49 views

How a switching mixer works in this example circuit?

I am reading about lock-in amplifiers and came across this example circuit of a mixer: You have one sinusoidal input signal $e_1$ with a phase $\phi_1$ and the local oscillator has a square-wave ...
NeonGabu's user avatar
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2 answers
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EM wave emission from earphone wires due to varying current signal

if we listen to some audio signal on a wired earphone, then does the wire of the earphone act as a transmitter antenna to emit the audio signal as radio waves even though its strength might be ...
sab's user avatar
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1 answer
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How is gradient magnetic field generated in MRI scanner, considering 0 divergence

During the phase and frequency encoding process of MRI scanner, gradient field with a gradient is applied along the direction to change kx and ky of spins at different spatial location. I am confused ...
Yan's user avatar
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1 answer
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Saturation region of common emitter BJT

About the saturation region of common emitter Bjt it's written that In saturation mode both of the "diodes" in the transistor are forward biased. That means V(BE) must be greater than 0, and ...
Alex's user avatar
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1 answer
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When forming an n channel in an N MOSFET, do the pn junctions of the drain-substrate and source-substrate parts disappear?

When forming an n channel in an N MOSFET,, do the pn junctions of the drain-substrate and source-substrate parts disappear? Here's what I expected: When gate voltage (higher than threshold voltage) ...
KHJ's user avatar
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5 votes
2 answers
135 views

What is the "closed circuit" of a bug swatter racket?

There are bug swatter racket that can kill fruit flies, mosquitos, or flies, if the insect touches the metal mesh. However, when I look at the construction of the device, the metal mesh is all one ...
Stefanie Gauss's user avatar
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1 answer
50 views

Is the direction of base current always constant in a BJT transistor?

Is the direction of base current always constant in a BJT transistor? Excluding the transistor breakdown state, is the direction of the base current always the same in the four modes: active mode, cut-...
KHJ's user avatar
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2 votes
1 answer
155 views

Voltage across the diode?

Why the voltage across an ideal pn junction diode remains 0.7 volts, even when the applied voltage exceeds 0.7 volts? Shouldn't it be the applied voltage minus the 0.7 V?
Alex's user avatar
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2 votes
1 answer
185 views

What can cause a spot above my WiFi router's antenna? [closed]

Lately a weird dark spot has appeared right above the antenna of my wifi router. It wasn't there before. I have tried to wipe it and it got a little bit brighter but I don't think it's dust. My guess ...
Szil_K's user avatar
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1 answer
93 views

How does an antenna work?

I'm looking for a model of an antenna that would explain how it works an in particular where the values of impedance like 36.5 ohms come from. I've tried looking but everything i found was overly ...
Jan Szwyngel's user avatar
0 votes
1 answer
31 views

Mesh current analysis but with variable resistors [closed]

I can't seem to be able to introduce V0 here! Here was my working out, using 3 mesh and 4 node equations. Only one mesh equation has V0 but it doesnt seem possible to introduce it into the rest.
user832075's user avatar
-2 votes
1 answer
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Why we are using coupling capacitor in AC amplifier? [closed]

Why we are using coupling capacitor in AC amplifier?
Akshai PS's user avatar
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0 answers
84 views

Magnetic force acting on a current loop while next to a current carrying wire

With I1=20A and I2=30A, find the net magnetic force acting on the loop. I am not sure how to even approach this problem. I know that the magnetic field of the wire is $\frac{\mu_0I}{2\pi r}$ and that ...
Z -'s user avatar
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0 votes
2 answers
41 views

If we change the direction of the connections in a step-down transformer, will it become a step-up transformer?

If we change the direction of the connections in a step-down transformer, will it become a step-up transformer?
Akshat Parmar's user avatar
0 votes
1 answer
27 views

Why my DC thick charging cable is slower than a thinner one? (having same power rating & adaptor)

Does that means thick wire cause more current loss than thinner one?
Aarav Raj's user avatar
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0 votes
1 answer
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How are quantum gates encoded in voltage/current waves for superconducting qubits?

From what I understand, the voltage and current waves propagate down the input transmission line, hit the nonlinear oscillator, and then bounce back toward the generator. How are gates such as the X ...
David L's user avatar
22 votes
12 answers
8k views

How do computers store sound waves just by sampling the amplitude of a wave and not the frequency?

All of this just doesn’t make sense though. I mean, doesn’t the amplitude represent the loudness and the frequency the pitch? Aren’t they completely independent from each other? Is the book just ...
RedP's user avatar
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0 answers
52 views

Power dissipated in transmission cable

Taken from NSAA/ENGAA 2022 (University of Cambridge's admissions assessments for Natural Sciences/Engineering) Electrical energy is transmitted at high voltage to a remote farm using an overhead ...
Daniel Williams Ruiz's user avatar
0 votes
2 answers
193 views

Resistors in high frequency

My question is this: Can we use ordinary resistors like those we use in labs(1.2K ohm), in high frequency (like 4GHz)?
Hamidreza Moosavie Arsenal's user avatar
3 votes
3 answers
400 views

How are photodiodes fundamentally calibrated?

I have a theoretical question regarding the irradiance measurement of light sources. From the basics I know the following: Irradiance has the unit $\frac{w}{m^2}$, in the context of light that means: ...
iwab's user avatar
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-1 votes
2 answers
179 views

Working of transistor

For the operation of the transistor, the base-emitter junction is forward-biased and the Base collector junction is reversed-biased. Due to the concentration gradient, electrons from the N side (...
Akshat Shrivastava's user avatar
2 votes
0 answers
96 views

Why Faraday homopolar generator need brushes?

It is said that if one would attach a load physically to the rotating disc from center to rim no current would flow because both in the load wires and the disc itself currents would be generated in ...
Jarosław HboRodo's user avatar
0 votes
1 answer
93 views

What is "capacitive effect" in terms of battery research?

For example, the paper I am reading states that the current was "periodically interrupted without changing polarity" to "demonstrate that the peaking behavior is not due to a capacitive ...
Alexis_Rose's user avatar
0 votes
0 answers
70 views

Help understanding why built in voltage in PN junction created?

I was reviewing basic semiconductor physics and need some help understanding where my logic is incorrect. For a basic PN junction, the process of forming the depletion region is described as follows: ...
fordanjen's user avatar
0 votes
1 answer
70 views

Doubt on time invariant system

Now I am delaying the output of a system (which takes $x \left( t \right)$ as input and gives $t \cdot x \left( t \right)$ as output) by $T$ then final output is: Let's denote the output of the ...
Qwe Boss's user avatar
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0 answers
72 views

Why there is no EMF induced in this circuit

Why there is no current flow in this circuit? On this diagram, the copper wires are long and extend far beyond the magnetic field range and they rotate with multimeter or BT transmitter, magnet is ...
Jarosław HboRodo's user avatar
-1 votes
2 answers
72 views

From the physics standpoint, how should I align a USB Internet stick relative to the nearest cell tower in order to have the best signal? [closed]

I use this USB Internet stick: (Huawei E3372h-153) To connect to the Internet, I simply insert a SIM card into this stick and then insert the stick into a USB port of my laptop. Based on my ...
Mitsuko's user avatar
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4 votes
4 answers
764 views

Load Lines and Characteristic Curves

While studying electronic circuits involving diodes, I came across the concept of characteristic curve, which relates the voltage drop in a diode with the current through it. However, I was also ...
V Govind's user avatar
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0 answers
25 views

Why do we still consider a doping concentration in undoped MOSFET devices?

I am studying cryogenic behaviour of MOSFET devices especially the evolution of threshold voltage with temperature. I mostly measure FinFET and FDSOI devices, all which have supposedly undoped channel....
Heomond's user avatar
2 votes
2 answers
94 views

How to collapse telescope image cone into an optical fiber?

I have an application where a telescope will be receiving light from a laser source. I would like to couple the output of the telescope, which is the image cone, into an optical fiber. Does anyone ...
Anthony Knighton's user avatar
2 votes
2 answers
92 views

Does KVL don't hold in pn junction reverse bias?

Does KVL hold in pn junction reverse bias because any reference about semiconductor physics provide that figure if we apply KVL around the loop won't be zero it will be equal to $V_{bi}$ then how KVL ...
amin's user avatar
  • 597
1 vote
1 answer
38 views

Does the built-in potential inside a diode change by making bias?

under thermal equilibrium the pn junction have a built-in field let say it's $E_{1}$ , if we make a reverse bias the external battery provide a permanent field $E_{2}$ , so the total field inside the ...
amin's user avatar
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