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Questions tagged [electrical-engineering]

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3answers
334 views

Water turbine power generation for large and small turbines

If you have a small water turbine and a larger water turbine in a river, would the larger turbine produce more power or would they produce the same because of the equal speed of the river?
2
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1answer
4k views

How does a work function difference cause band bending in equilibrium in Metal-Oxide-Semiconductor (MOS)?

How does a work function difference cause band bending in equilibrium in Metal-Oxide-Semiconductor (MOS)? I don't understand the physical meaning behind this sentence from Sze: to accommodate the ...
2
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1answer
60 views

Does it cost more energy to turn on a CFL globe than it is to leave them on?

Say there is a 15 W CFL globe. When turned on for an hour, it consumes electricity worth $10 in terms of energy consumption (made up cost for simplicity). If the occupants of the room periodically ...
1
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1answer
621 views

Calculating the strength of the electric fields between the plates if the dielectric between the plates is air

This is one of the questions from my textbook with no solutions. One plate of a capacitor carries a charge of $+0.567\space pC$. The other plate carries a charge of $-0.567\space pC$. If the ...
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1answer
22 views

Voltage supply used in main supply

why should we use voltage rms (V rms) besides peak voltage (V peak) for main supply? What is the different that might be occur?
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2answers
4k views

What exactly is a phasor?

What exactly is a phasor? I was reading about alternating current when I came across the following definition: A phasor is a vector which rotates about the origin with an angular speed(suppose $\...
43
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3answers
38k views

Why do we use AC for long distance transmission?

Why do we use AC (Alternating Current) for long distance transmission of electrical power? I know that AC is such a current that changes polarity (magnitude and direction) and has fixed poles.
2
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1answer
114 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 ...
3
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1answer
85 views

Railway line conundrum [closed]

I found a wire joining those 2 cement slabs. I wonder what it does. Any ideas?
9
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3answers
4k views

Can a television detector van REALLY tell if you have the TV switched on? [closed]

In the UK, it was regularly advertised by the BBC, and the Post Office, that they had vans that could check if your TV was on, even if you were in an apartment block full of other people's TVS. TV "...
0
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1answer
13k views

Equivalent resistance of unbalanced Wheatstone Bridge [duplicate]

Equivalent resistance of a balanced Wheatstone Bridge is pretty simple: if the corresponding ratios are equal the just cancel the wire connecting the centre of two wires. But what if they are not ...
1
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3answers
2k views

Why does a charged particle in a cyclotron moves in circular path?

Force on the particle is charge*(velocity×magnetic field intensity). The magnetic field intensity is perpendicular to velocity of charged particle. What is it that makes it move in a circular path?
0
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1answer
69 views

Power factor effects and causes

Why do power utilities impose power factor penalty when power factor goes low (less than 0.7)? Why does the power factor get smaller when the load is much less than the max or rated power of ...
0
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3answers
74 views

A logic question on binary variables

I recently purchased some nightlights with sensors. The sensor will make sure the nightlight will only be tuned on in a dark environment. Let's assume the sensor is binary, ON or OFF. Here is the ...
0
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1answer
87 views

holes in an electronic circuit [closed]

Many times, by looking at electronics circuits I noticed that they have like small holes printed in yhem. The question I want to ask is, what s the purpose of these holes?
0
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2answers
1k 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 ...
0
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0answers
112 views

Why is the satellite dish still needed?

How much does it amplify the signal? The receiver cannot pick up the signal without the dish? Is it possible that it will disappear in 10 years? As the sensitivity of the receiver is enhanced? ...
1
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2answers
2k views

Electronics book for physics undergraduates

I am going through very hard time studying electronics, I studied little electronics at high school (what is diode, transistor, etc). Now in clg now I need electronics to study, I don't understand ...
1
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1answer
177 views

Normalizing temperature data of CPU sensors to ambient [closed]

My scenario: I want my application to stop or take some decision based on temperature. say like if my ambient is morethan 41 i want to switch off the application and we do not have an separate ...
0
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1answer
75 views

Accelerating Hard in an EV More Wasteful?

Is accelerating hard in an electric (or any, for that matter) vehicle any more wasteful than accelerating slowly? My flimsy grasp of physics suggests that it shouldn't be. The energy required to ...
1
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2answers
660 views

Kirchhoff's laws in phasor domain

While analysing AC circuits, we write voltage, current etc all with complex numbers namely "phasors". While studying the same, I wondered if Kirchhoff's laws held good with current and voltage in ...
0
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2answers
27 views

Electrical Insulators

I was wondering what happens to the electron after it leaves it's valence shell and strikes a stable valence shell; in an insulating material? I realize that the energy from the strike, is absorbed by ...
0
votes
1answer
130 views

What is the physical mechanism of power transfer in the primary of an ideal transformer?

In an ideal transformer, the mutual induction caused by the secondary load current in the primary coil generates an additional current that has a non-zero power factor with the main AC voltage source. ...
0
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1answer
116 views

What is time badwidth product for pulses with GDD?

For a gaussian pulse the time bandwidth product is dwdt = 0.4. What is the time-bandwidth product for chirped pulse with group delay dispersion (GDD) added only ?
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0answers
121 views

Physics of the capacitance of an electrolytic capacitor

In explanations about the electrolytic capacitor one often cites the formula $$ C = \epsilon_r \epsilon_0 \frac{A}{d} $$ for the capacitance $C$. Then one says that by enlarging the area $A$ via ...
1
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1answer
97 views

Voltage and reactive power

Why are reactive power and voltage related? When the control system of a generator increases/decreases the current of the rotor, voltage and reactive power are increased/decreased.What is the relation ...
0
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2answers
8k views

Why fuse needs to be slightly more able to bear current than the appliance?

if I have a bulb with rated current of $4 A$ then why I need to connect an $5A$ fuse?( which has slightly more ability to bear current.)
2
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0answers
97 views

Can seebeck chips be used to extract Peltier chip waste heat?

I understand that a problem with employing the Peltier effect for the purpose of cooling is that it produces a significant amount of heat on the hot plate. But why don't we use seebeck optimised chips ...
6
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3answers
2k views

What happens after an electron and hole combine?

OK so I understand that an LED is a pn junction where when a forward bias is placed across the junction, the electric field causes the electrons to combine with the holes and release a photon through ...
0
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2answers
670 views

Can an Oven being set to a different temperature cause electric board to go off?

Basically: the electrical system kept going off (when light goes down in a division due to too many electrical appliances on at a time, or their combined power consumption). My roommate said it was ...
1
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0answers
92 views

Which law of physics is applicable for communication? [closed]

What is the physics behind communication like internet, mobile phones etc. What are the equations?
1
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2answers
93 views

When heat loss is more than energy generated [closed]

Suppose a electric power station produces 200W of electricity @ 200V. Now instead of stepping it up, it decides to transmit it as 200V to a city 20 km away. The transmission cable has resistance per ...
0
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0answers
32 views

Separating Interaction of Heat from Electricity?

I have a rod where electricity of frequencies 1-360 Hz is passed through. It is affected by heat. I am evaluating the energy involved in such a process, contributed by electricity and heat. The ...
1
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4answers
2k views

Voltage of a battery in a circuit with an infinite resistance [closed]

I have a dilemma that I would like to share with you concerning batteries (without neglecting internal resistance), emf and resistance of a circuit. To better visualize my question you may need to ...
1
vote
1answer
129 views

Estimate battery's real capacity in real time [duplicate]

The maximum capacity of a battery during usage can vary from manufacturer's specifications due to factors like temperatures and battery health. Because of that i want to estimate the real maximum ...
1
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0answers
30 views

Electron , collision , current , dual nature [closed]

My question is regarding fundemantal concept. I am good in kcl and kvl delta to y resistor rcl and rl circuits machines etc but as i read drift velocity i get so many questions. We are reading since ...
1
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1answer
325 views

Will an Electrical Engineering Minor give me a significant advantage in experimental physics? [closed]

I'm currently choosing courses to complete in my university degree (science) and thought completing some basic electrical engineering may be useful if I go into academic experimental physics research. ...
2
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0answers
180 views

Estimating the battery capacity using current power consumption and battery percentage

I want to estimate the current maximum capacity (in kWh) having the current power consumption (in kWh) and the state of charge of the battery (in %) available in a time series. I do not have a full ...
4
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2answers
560 views

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 ...
1
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1answer
84 views

Why do scientists measure fundamental constants so precisely?

According to the last CODATA report the charge of electron is measured very precisely (10 decimal places). And it's not only about the charge of electron. Why do scientists measure fundamental ...
-1
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1answer
1k views

Why does the symbol have an arrow? [closed]

What does the arrow in the symbol mean? Does it mean that it is a variable voltmeter and ammeter?
17
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2answers
8k views

Why don't they use springs as an energy source for cell phones?

I know they used springs for clocks way back in the day and now it's all lithium ion batteries. For reference, consider the Iphone that has a battery with a capacity of 5 Watt hours (18,000 joules). ...
1
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1answer
42 views

Why current of a battery drops continuously in high currents?

I have asked this question on EE SE but could not get a satisfactory enough answer. I have shorted an AA battery through an ammeter. Inititially, the current reading on ammeter was around 0.9 amperes ...
1
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1answer
414 views

Laser-induced electrical discharge

Attracting lightning with an ion beam has been done in a lab but how strong of a laser is needed to reach the clouds to redirect the lightning bolt?
2
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1answer
610 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 ...
1
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0answers
2k views

Exact (quantitative) definition of “knee” and/or “cut-in” voltage?

Sort of a 2-part question: 1) I know they are used interchangeably but are the "knee" and "cut-in" voltages of a diode actually the exact same thing? I had thought that the "cut-in" voltage was ...
0
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2answers
49 views

Electricity from something other than a solid

Is piezoelectricity only limited to solids or can liquids or non-Newtonian fluids create a current when compressed?
2
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2answers
225 views

How many photons does my remote control garage opener emit?

Every time I drive up to my house I imagine all the photons spitting out of the remote control garage opener when I press the button. And I imagine the door opener in the garage receiving them. There ...
1
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1answer
335 views

Reference for Kirchhoff's Circuit Laws

Does anyone know the reference where Gustav Kirchhoff published his famous circuit laws?
0
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1answer
403 views

Attenuation and Amplification - Transatlantic telecommunications cable system

It's a german book so I don't know if I'm translating this properly into english, so bear with me: The TAT-14 connects the cities Norden and Tuckerton with glass fibers (~7500 km). The cable has ...