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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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 ...
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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, ...
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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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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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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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Why is there an electric field but not magnetic field on the LHS of the integral form of Faraday's Law
Just started to learn Electromagnetism, and didn't quite understand, please help correct my misunderstanding:
The lectures said that the electromotive force (e.m.f), was
$$
{\cal E} = \oint \vec{F} \...
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What is the formal definition of capacity fade?
https://www.ipaceforums.co.uk/threads/capacity-fade-vs-power-fade.6794/
According to this post capacity fade is defined as the percentage of total capacity left. So I'm assuming it would be calculated ...
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Curl of current density in a wire with variable cross section
We have a wire with the shape of a cone. The cone is aligned along the z-azis. Major radius $r_M$ and minor radius $r_m$ and length $l$. An electric current $I_0$ is injected at the bottom. We could ...
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Do flourescent tube lights create magnetic fields like other conductors?
So, does every electron flow also have a corresponding magnetic field to go along with it, or is magnetic fields only a property of solid metal conductors?
Also, what about lightning?
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Can you loop a charge pump?
Is it possible, to charge two capacitors in parallel(eg. each two volts). Discharge them in series to a third capacitor(4 volts). Charge the first capacitor again with the initial voltage(2 volts). ...
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Currently arguing with my teacher about this electromagnetism question, any helpers?
Sorry if my Q is simple, I'm still in high school.
I'm currently arguing with my physics teacher regarding a Q, shown below.
The answers state this.
However, I am attempting to argue that the ...
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What happens to the charges in an inductor when you induce a voltage?
Say you have two inductors, and - very much like a transformer - you connect the first one to a voltage source, then place the other one close to it, so that there will be an emf induced by the change ...
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How can I calculate the magnetic field of a plasma?
If I created a plasma and put a large electric current through it would a magnetic field be created? If so how large would this field be and how can I calculate it?
For example, we put 1000 amperes ...
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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,...
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Battery in non-closed circuit with charged body and Earth
Looking at the clips on how the battery works, I understand that eventually one of the ends releases the electrons which then move through the conductor to the other end, to continue the reaction. Now ...
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Could you make a fire torch with electricity? [closed]
Similar to a blowtorch, is there a way to generate a flame without using gas or liquid fuel(like butane, propane, etc)?
(source)
For example I'm thinking about those portable air heaters, could one ...
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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.
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Were radioactive materials used in neon indicator lamps? [closed]
Were radioactive materials used in neon indicator lamps?
Old-fashioned glow starters for fluorescent lighting
[How a glowstarter works]
often contain small traces of radioactive gas (like $^{85}$Kr or ...
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Confusing definitions of EMF
I was studying about EMF (electromotive force) recently but had trouble connecting the two definitions of the topic. Here are the two definitions of EMF listed in my book (The book I've referred is: ...
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Can a satellite generate electricity by using a planet's magnetic field? [duplicate]
I am entering AP Physics E&M and don't have much knowledge about electricity but always had an idea based on my limited knowledge.
If a satellite had a metal coil inside of it, wouldn't it have an ...
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Understand power rating in layman terms
I have recently started the chapter of electricity of class 8. I am not understanding the concept of power rating of appliances. When we say that a bulb is rated 220V-100W, which means, according to ...
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Volume distribution of charge in a wire in a DC circuit
According to this and several other articles some amount of charge in a DC circuit distributes itself on the surface of the conductor, making the electric field inside parallel to the said surface.
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How do I compute the voltage accross a cell membrane given microstate of neuron (distribution of charged ions)?
I am not a physicist, and I'm not sure what keywords to use to search for this.
I'm trying to understand how I could in theory quantitatively know, what the voltage across a cell membrane in a Neuron ...
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Do we have to provide energy to move electrons in an electric field?
In the positive and negative terminal of a battery, there is potential difference due to the accumulation of charges in their respective terminal, so it created a potential difference, and if we ...
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Induced charge on conducting sphere sliced by a plane
We are given a conducting solid sphere, and it is cut by a plane as shown.
A charge $Q$ is given to the smaller part of the conductor, and it is required to find the induced charge on the surface of ...
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Gibbs phase rule argument about battery voltage dependency on the state of charge
I'm studying battery physics, particularly the dynamics of full discharge, and I am having trouble understanding an argument that is based on the Gibbs phase rule
$$F=C-P+2.$$
I understand the phase ...
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Does all the Energy provided by the battery dissipate into heat?
Before proceeding onwards please note that I am talking about a simple circuit consisting of an ideal battery, a switch and an external resistance.
So I was told that $$ W_\text {ideal battery} = Q_\...
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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 ...
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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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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 ...
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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 ...
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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 ...
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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 ...
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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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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 ...
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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 ...
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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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Anode/cathode in an electrolytic capacitor during discharge?
Wikipedia says "an electrolytic capacitor is a capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer" (1, link). Elsewhere, wikipedia seems to ...
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