Questions tagged [electricity]
The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
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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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Heating a Material with Negative temperature coefficient of resistance
TCR (Temperature Coefficient of Resistance): $R = R_0[1 + α(T - T₀)]$ Where: $R$ is the resistance at temperature $T$, $R_0$ is the resistance at a reference temperature $T_0$, $\alpha$ is the TCR of ...
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I don't understand how current always chooses the path of least resistance [duplicate]
As the question states, I don't understand how Current always chooses the path of least resistance.
How does it even "know" to pick that path
For example, if we have a short circuit which ...
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Modeling an Electrolyzer System
In this study, the authors provide an equation for operating cell voltage: $V_{cell} = V_{rev} + V_{act} + V_{ohm}$, the sum of the reversible overvoltage, the activation overvoltage and the ohmic ...
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Why do charges exist in the first place?
Why do charges exist, how did they come into existence? (if any theories exist, then please explain them in somewhat detail)
What would happen if charges never existed?
Please explain the answers at ...
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How is electrostatic force 'lost' during conduction in these examples?
When you rub a glass rod against silk cloth, the glass rod becomes positively charged and the cloth becomes negatively charged. So they now can attract each other.
However, after this 'attraction' ...
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Why doesn't charge accumulate in a loop?
When learning about electromagnetism at my university, electricity flow is generally shown as a conductor with a high potential at one end and a low potential at the other and thus charges flowing ...
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Trouble understanding an example in electricity and magnetism by M.Purcell
I'm having trouble understating the following example in section 3.2 of electricity and magnetism by M.Purcell:
In paragraph 2 of the solution, it states that "The combination of these charges ...
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Why are the formulae for the electric flux density and the magnetic flux density fundamentally different?
I've been delving a bit beyond just using what's typically given as the "electric field" and "magnetic field" in various problems, and finding out about the various more ...
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What happens to the charge which enters the positive terminal of the battery in a circuit? [duplicate]
SO basically , I know that a battery creates potential difference or V in a circuit to flow, by doing work on the charge(electrons) . The motion of the charge(electrons) is from the -ve or negative ...
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Is electric current actually the flow of electrical charge?
In my high school, the definition of electrical current is "the flow of charges" but I have seen a video about how electricity actually works and it seems to me that electrical current is ...
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Would this simple design function as an electromagnet?
I was thinking about electromagnets today and a thought popped up in my mind on what would be a very simple way to create an electromagnet.
Although I have not built and tested it, I am pretty sure ...
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What is actually electric current? [closed]
Electric current is the rate of flow of charges (electrons) or the rate of flow of positive charge. Okay, I get it. But here's my question. The electron flows in the wire and then the current flows in ...
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The inequality relation between the e.m.f. of two cells and the equivalent e.m.f
Consider two cells of e.m.f. $ε_1$ and $ε_2$ with internal resistances $r_1$ and $r_2$ respectively set up parallel to each other in a circuit as shown in the figure:
Let the equivalent e.m.f. be $ε_{...
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Electrical energy is $I^2Rt$, and heat dissipated is also $I^2Rt$?
My book says:
Let a current $I$ be flowing through a conductor of resistance $R$ for a time $t$, when a source of potential difference $V$ is connected across its ends.
Then, it proceeds to prove ...
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Does the position of the fuse affect whether the bulb or the fuse would blow first?
If I connect a fuse and a bulb in series with:
fuse to the live and bulb to the neutral
fuse to the neutral and bulb to the live
During an overloading would this cause:
the fuse to blow and ...
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Why should the heating coil of a heater have high resistance?
In my book, it is given:
The resistivity of an alloy is generally higher than that of its constituent metals. Alloys do not oxidise (burn) readily at high temperatures. For this reason, they are ...
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Force on charge carriers in a simple circuit
Is it true that in a simple circuit where a simple conducting wire is connected to a battery, the force on each charge carrier is same in magnitude ? If yes, then can you explain how? I know that if ...
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Why does the power loss in transmission cable increase when resistance is increased?
In transmission cables, why does power loss increase when length of conductor is increased? According to the formulas V=IR and P=I²R, When we increase the length, the resistance increases, while the ...
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Current density of moving charge distribution - mobile charge density vs. "ordinary" charge density of the distribution?
in Introduction to Electrodynamics by David J. Griffiths I have latched upon this definition of current density vector $\mathbf{J}$ (Chapter 5, section 5.1.3, p. 220 in 4th edition) and I would ...
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Electric current density definition
I'm just wondering why the current density $J$ is always defined as the amount of electric current traveling per unit cross-section area $J = \frac{I}{S}$, and not per volume unit $J = \frac{I}{V}$ so ...
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How to compute the resistance of a nonuniform cylinder with varying resistivity?
The generally quoted formula foe resistance is
\begin{equation}
R = \rho \ell/A
\end{equation}
some special cases are easy to solve. For example the case where the current flowing along the z-axis and ...
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