# Questions tagged [electricity]

The study of the presence and flow of electric charge. Charges, currents, fields, potentials.

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### Apparent mathematical contradiction regarding constant potential inside conductor - what am I missing?

I know that the electric potential inside a conductor is always constant, regardless of anything surrounding the conductor. Mathematically, I don't see how this makes sense. Please consider the ...
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1 vote
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### What I think about surface charges in electrical circuits

Assume We have a simple electrical circuit with a DC Source of constant emf. And I am talking about the ideal case. The circuit also consists of "Push-Key" or a normal switch whatever you ...
38 views

### What is the angle used in the scalar product of vectors A and B? [closed]

I assume it’s 120 degrees but I’m not sure; vector A is 30 degrees from vector B, which is perpendicular to the surface of the hemisphere
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### Measure real corona discharge intensity, range 2000-7500V?

I need to measure the actual corona discharge intensity produced by a particular circuit and electrode array. I'd love numbers as hard as possible, though am not sure what units apply; alternatively, ...
1 vote
82 views

### How do circuits work at a subatomic level?

I imagine it’s like this. Let’s say we connect a copper wire to a battery’s terminals. The electrons from the negative side will thus exert a push on the electrons near the wire and it will continue. ...
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### Do wind turbines spin at constant speed? If so, how? [closed]

All electrical power fed into the electric grid needs to be an AC power source at 60 Hz (in the U.S.) to within a very tight tolerance. My understanding is that steam turbines are kept rotating at a ...
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1 vote
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### Why are electrons in a wire so slow and what exactly makes them move?

If one applies an electric field to a conductor, then the electrons inside it will start moving around, until the field is balanced out to 0. It is said in Griffiths’ “Intro to E&M” that this ...
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1 vote
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### How Are Fractal Wood Burning Patterns produced by DC Electricity?

Here are 3 typical videos of fractal wood burning: video 1, video 2 and video 3. As can be seen in all the videos, the different Lichtenberg figures develop simultaneously from both the positive and ...
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### Is there simple harmonic motion when a dielectric longer than the capacitor is inserted into the capacitor? [duplicate]

I’m trying to understand the mechanics of a dielectric being inserted into a parallel-plate capacitor. Suppose I have a parallel-plate capacitor with plate separation d and a dielectric slab of length ...
44 views

### Why does the electric field only depend on the rod?

In the following exercise: We are asked to calculate the electric field at a certain distance from an exis where a rod is located. Previously, we are asked to calculate the charge density a ...
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120 views

### Is the Lorentz force proportional to $B$-field in the wire or immediately outside of it?

When considering the force on a current carrying wire in a magnetic field, is $B$ in the Lorentz force $F=IlB$ the field inside the wire where the current is flowing, or is it the field immediately ...
17 views

### Resolution of current in solenoid in order to analyze magnetic field?

So i came across this question in one of my tests, it asked something appearing very easy,It actually asked "If radius of solenoid is R and that of wire wrapped on it is r then comment about the ...
1 vote
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### Confusion about EM waves in a conductor, AC in wires, and skin effect

I am trying to get my head around these different points: From Maxwell's equations we find that an electromagnetic wave in a conductor decays in amplitude with a characteristic length of about 1 cm in ...
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### Are electrostatics conditions still valid in Current carrying conductors?

Question 1: How is steady Electric field generated inside a conductor ? Question 2: Why do we say that electrostatic conditions still hold in a current carrying conductor(drift speed is small ...
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### Predicting electrical mean free path in nanostructures?

How does one roughly predict the mean free path for electrical conduction in a nanostructure at different temperatures and under different electrical conditions such as different voltages and ...
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### Maximum mean distance electrons can travel in ballistic conduction?

How far in mean distance can electrons reasonably travel via ballistic conduction according to the current model and what is the current mean or average distance or length record for ballistic ...
1 vote
43 views

### Charge transferred from Sphere and Disc after being brought into contact

Recently I came upon the following question $-$ A conducting sphere of radius $R = 1 m$ is charged to a potential $V = 1000$ volts. A thin metal disc of radius $r = 1 cm$ mounted on an insulating ...
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### Atomic Level Explanation of Active Cathodic Protection

I was trying to understand why active current cathodic protection doesn't work for cars and I realized I don't really understand what's going on with cathodic protection at an atomic level. I ...
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### Why do different ways of calculating the new capacitance of a capacitor after being partially filled with dialectric yield different results? [duplicate]

I have encountered this problem that stumped me and my colleagues. It is expected to be solved by Physics II students. I tried asking some faculty members but to no avail. An air-filled parallel ...
1 vote
119 views

### Derivation and theory for $I = kV^n$ [closed]

I performed an experiment in college to study the nature of a filament of a lamp, determine $k$ and $n$ in the relation mentioned, and study the variation of wattage of a lamp. I assume ohm's law is ...
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### Why is the energy lost by an electron in passing though the LED = energy of the emitted photon?

I understand that the energy of the emitted photon = energy between the conduction band and valence band, but why does the work done by pushing the electron through the depletion region equal the ...
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### About lightning and lightning conductor

Lightning not only strikes on a lightning conductor installed on the building... Lightning can strike anywhere on the surface roof of the building even though that building has installed a lightning ...
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1 vote
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### What limits the size of a nuclear power generator?

Nuclear microreactors like Westinghouse's eVinci are small enough to fit on a flatbed semi-truck, and NuScale Power's small modular reactor (SMR) is small, too; but are there smaller nuclear power ...
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### If metals can’t sustain an electric field inside them (as their electrons move to cancel it out), how do they still conduct electricity? [duplicate]

I tried to understand by my own couldn't do so.
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### Why is current through the short circuited wire not zero? [duplicate]

Why does current flow in a short circuited wire? I understand that it offers negligible resistance to the flow of charges, but two points on the short circuited wire will have the same potential, so ...
70 views

### If there's magnetic field around current-carrying wire, why doesn't it always exist?

Motion is relative. If we say train is moving, it moves with respect to the Earth. If we are inside, it doesn't move from our point of view. Then, with respect to what object do we say that electrons ...
1 vote
42 views

### How much energy does a single lightning bolt from this Van De Graaff generator consume?

I recently visited the Boston Museum of Science and saw a show using their "world's largest air-insulated Van de Graaff generator." I was curious as to the actual energy output of the ...
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