Questions tagged [electricity]
The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
4,055
questions
4
votes
1
answer
195
views
Superconductors and electrical fields
I have been looking around to figure out how superconductors are made. What ways are there to create a superconductor that don't involve a coolant like liquid nitrogen? Is it possible to cause a ...
- 512
1
vote
3
answers
1k
views
Problem with an electricity / thermodynamics assignment
I've been trying to figure this one out for a while on my own, so I'd like to ask for your help if you could offer some.
The task states:
A heater made out of a wire with a diameter $R = 0.2\text{ mm}...
- 145
9
votes
2
answers
8k
views
How can a conductor be grounded yet there are induced charges on it?
A classic example for the method of images is the following, quoted from Griffiths's Introduction to Electrodynamics, page 121:
Suppose a point charge $q$ is held a distance $d$ above an infinite ...
- 17.1k
11
votes
1
answer
1k
views
Explanation for speed of an electrical impulse
Our calculus book, Stewart, has a problem where they claim that for a metal cable (inner radius $r$) encased in insulation (outer radius $R$), the speed of an electrical impulse is given by
$$v = - k ...
- 111
2
votes
4
answers
37k
views
domestic electric AC wiring - Live and Neutral correct or not? [closed]
On electric circuits, with $120$ or $230$ AC mains, there are the wires Live and Neutral.
The wiring isn't symmetrical : following the circuit, you cannot switch $L$ and $N$.
However, in Italy, ...
- 129
33
votes
11
answers
35k
views
What is the difference between electric potential, electrostatic potential, potential difference (PD), voltage and electromotive force (EMF)?
This is a confused part ever since I started learning electricity. What is the difference between electric potential, electrostatic potential, potential difference (PD), voltage and electromotive ...
- 439
1
vote
1
answer
3k
views
How does the X-Y mode of an oscilloscope work?
I recently used an oscilloscope in X-Y mode to draw the phase ellipse of two voltages. I then used the formula $\phi = \arcsin(2y/B)$ where $y$ is the value of the ellipse at $x = 0$ and $B$ is the ...
user714
15
votes
6
answers
30k
views
How do you determine power flow direction in a transmission line?
Below is a picture of a typical transmission line(about 200 kV). Is there a simple physics experiment which can be performed safely near the line, to determine the power flow direction. Or in other ...
- 2,697
3
votes
5
answers
93k
views
What is the relationship between AC frequency, volts, amps and watts?
In an alternating current, how are frequency, voltage, amperage, and watts related?
For instance, imagining the power as a sine wave, what is amperage if voltage is the amplitude? Is there a better ...
- 157
1
vote
1
answer
1k
views
How to teach the concepts of "Electric Potential" & "Potential Energy" to 10th grade students
I've got to teach the concepts of "Electric Potential" & "Potential Energy" to 10th grade students. I don't understand how to express these things and make them understand.
“If you can't ...
- 7,335
6
votes
1
answer
11k
views
When does voltage drop occur?
Why or when does it occur in a circuit? What does it imply when you speak of a voltage drop across a resistor? (Obviously, it probably means that the current's voltage before the resistor is higher ...
- 1,887
1
vote
1
answer
8k
views
Would a generator in vacuum/space provide electricity endlessly?
At it's simplest, electricity generation is achieved by induced voltage due to a changing magnetic field. In a vacuum in the absence of friction, would the initial spin imparted to the rotor of a ...
- 4,723
2
votes
0
answers
404
views
Schottky and shot noise
I am looking for a little history on shot noise: when was it first predicted and first measured?
In particular, what was the role of Schottky? His 1918 paper "Über spontane Stromschwankungen in ...
- 9,541
2
votes
1
answer
390
views
Circuit Simulation
I am making a circuit simulation program, and I am not sure how to simulate the behavior of Diodes.
Take this circuit:
&...
- 123
7
votes
3
answers
4k
views
What's the source of electricity for the human brain?
I keep hearing that there's always electrical activity taking place inside the human brain. Our heart and various other organs function because it receives electrical signals called impulse. But, what'...
- 472
3
votes
2
answers
1k
views
Electrostatics:Basic question on electric current
I've got two questions for you.
Electric current is the flow of electrons across a conductor.Why has it always got to do with electrons and not with protons? (I know neutrons are not eligible for ...
- 472
9
votes
2
answers
8k
views
Tying knots in power cables to prevent power surge from lightning strikes
There are plenty of references to this claim on the internet that tying knots in power cables will prevent a piece of equipment e.g. television or computer from a power surge.
How can this be ...
- 191
3
votes
2
answers
537
views
How to measure faster than light electric energy?
According to relativity,nothing can break light barrier.But a recent preprint shows energy transmission of commercial electric power (f=60Hz) is faster than light. (It is not the drift velocity of ...
- 31
5
votes
3
answers
4k
views
Why are downed power lines dangerous?
A friend of mine was telling me about a storm that knocked down a power line over at their place, and it got me to thinking. Why are downed power lines dangerous? I don't see any good reason for it.
...
- 2,172
2
votes
2
answers
319
views
Introducing emf of a chemical cell as a hint towards quantum mechanics
Today I had a discussion with a colleague who teaches electricity and magnetism to 2nd year undergraduate physics students. He is seeking the best way to explain how is the emf generated inside a ...
- 4,453
3
votes
3
answers
2k
views
How can two different 12V batteries have different amperage for same resistance?
My local car parts dealer presented me his inventory of car batteries. One 12V battery had a 'cold crank amperage' of 600amps. The other 12V battery had a 'cold crank amperage' of 585amps. Questions:[...
- 303
2
votes
1
answer
408
views
Practical physics: where does this current come from?
It's been a while since school and I don't remember the right laws and formulas. So I come here. :)
I've got a power cord extender running from the wall outlet to my washing machine. It's about 3 or ...
- 3,101
3
votes
1
answer
311
views
What's the second terminal in corona discharge?
I don't get corona discharge. There's an electrode (say naked high-voltage wire) and a current develops from that wire and ionizes gas (air) on its way.
But where does this current go? What's the ...
- 831
2
votes
1
answer
11k
views
How to calculate the exit velocity of a coil gun projectile?
First off, what quantities need to be factored in? Voltage and current through the coils, the magnetism of the projectile, the magnetic fields, etc.? Next, how would you calculate the speed of the ...
- 197
4
votes
4
answers
24k
views
What happens if a wind mill rotates in opposite direction?
Suppose if a windmill is made torotate in clockwise direction and due to air flow if it rotates in anti clockwise direction then does it produce electricity?
- 307
1
vote
5
answers
113k
views
Charging 12V 150Ah battery [closed]
I want to charge a 12V battery of 150Ah with a solar panel. The solar panel specs is
12V, 25 Watt.
Can anyone please provide me how to calculate that how much time it will take to charge the battery? ...
- 149
4
votes
3
answers
1k
views
number of electrons my laptop uses in a second
in order to confirm whether I understand the relation ship between amps, columbs and electrons I decided to try out the following.
my laptop adapter's label reads 3.34 amps.
I assume that:
amps are ...
- 141
65
votes
6
answers
94k
views
Why do power lines buzz?
When near high tension power lines, particularly after a good rain, the lines themselves emit a buzzing noise. A similar noise can be heard coming out of the electric meters attached to my apartment.
...
- 750
0
votes
2
answers
277
views
Why only one prong in the plugs are not showing response to tester pen?
I have 2 pin outlet for A.C current . Now when I connect a TV plug in that and when I touch one of the prongs with my tester, the tester is showing response. But on the other prong the tester shows no ...
- 111
2
votes
1
answer
2k
views
Total power consumption of electric device
For some electric devices, like a fan or air conditioner, I read about their power consumption in watts on their specification guide.
Does it tell about the power at normal or full speed? or Does the ...
- 21