Questions tagged [conductors]
For questions about materials which allow the flow of an electric charge (electrical conductors) or the transfer of heat (thermal conductors) through them.
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Charge distribution: electrostatic equilibrium in conducting sphere
Consider an uncharged sphere, made of electrically conducting material. We then charge the sphere with excess charges.
I understand that these excess charges repel each other till the electric field ...
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Why Can The Charge Distribution of A 2D Conductor Be Determined By Flattening Its 3D Counterpart?
The most famous instance of this trick is probably in the case of finding the surface charge distribution of a charged conducting disc, where this disc can be perceived as a squashed down version of a ...
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Could you calculate the force between two NON-PARALLEL, straight current carrying wires?
Just like there are ways to solve for the force between two straight parallel wires, what is the way we could find the force between non-parallel wires?
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How does charge move in conducter which is between two connected conductors [closed]
Two square conductors with neutral charge and surface $A$ and $d<<\sqrt{A}$.
The conductor in the middle is the same shape but with a very small hight, $dh$, and is charged with $q$
How to ...
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Charged Cavity in conductor
Problem:
Suppose we have an isolated spherical conductor and a cavity that is not concentric. Then, a charge is placed at the center of the cavity.
What can we say about the distribution ...
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How do I calculate the surface potential of a conductor given a charge distribution?
I have tried the conventional definition but since there is a charge density at the point we want to calculate the potential at, it turns out to be infinity. Now, i dont know how to calculate the sum ...
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Two balls are attached with a very long and thin conducting wire to two conducting plates. How does the capacitor react in this situation?
The question is as follows (taken from a previous exam):
Two balls (conductors w/ Radius $R_1$ for left ball ball, $R_2$ for right) are attached with a very long and thin conducting wire to two ...
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Why do charges uniformly distribute themselves on the surface of a conducting sphere with a charge inside its cavity?
If we move the charge $+Q$ a little bit to the right or to the left, more negative charges will gather in the same direction, while positive charges on the external surface of the conductor won't move ...
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Why is there a band gap in semiconductors but no band gap in conductors?
At this point, I understand that at least one fundamental difference between conductors and semiconductors is that in conductors, there is typically no band gap because the valence band and ...
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Charge Inside a conducting hollow sphere
Let two concentric hollow charged conducting spheres of radius R1 and R2. If charge on inner sphere is Q1 and for outer it is Q2, wouldn't the resulting electric field due to the whole system be '0' ...
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Electric displacement field in a conductor
The photo given below is from the solution manual to Griffiths Electrodynamics, it claims that the displacement field inside a conductor a zero. Now I do not see why it is obvious ,
$ D = εE + P $, ...
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What is the electric field inside a perfect conductor connected to a DC source?
We all know from a course on electrostatics that the electric field inside a perfect conductor, placed inside a static electric field, is zero. Now imagine the same perfect conductor is connected to a ...
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Does net charge on a conductor sit only on outer surfaces?
Suppose we had a hollow conducting sphere with a net charge q on it. There is no charge in the cavity; the conductor itself has a charge q. The idea is that this net charge would reside on the '...
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Why force by electric field is appearing?
I want to ask about the Hall effect. Why is the force by the electric field appearing?
I can understand the appearance of the Lorentz force. However, I do not know for what reason the force due to the ...
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What is meant by a source-free conductor?
I have recently worked with a source-free conducting slab filled with free space and with an electric field inside, and I have determined the corresponding magnetic field from MW's eq's. Next, I ...
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Induced charge density on perfect conductor
Assuming there is a perfect conductor at $x=0$ in $\mathbb{R}^3$ and a plane EM wave $\vec{E}_i(\vec{x},t)=\vec{E_i^0}e^{i(kx-\omega t)}$ is coming from $x=- \infty$. We know, that the wave $\vec{E_r}(...
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Charge distribution on a torus (doughnut) shaped conductor
In a spherical solid conductor the charge is always on the outer surface. Even if the sphere has a cavity, the surface of the inner cavity can not carry a charge due to Gauss's Law.
What would be the ...
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How would surface dipoles change the internal potential in a conducting sphere?
In the nanoscience literature, there is a model of semiconductor nanoparticle doping which ascribes the effect to surface dipoles shifting the absolute state energies relative to the environmental ...
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Find the surface charge that appears on a cavity
The problem is of a conducting medium in a uniform field $E_0$. A spherical cavity of radius $a$ is formed inside said medium.
I already found the potential inside and outside the cavity
$\Phi_{\text{...
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Neutral conductor and charged insulator brought near each other
What happens when a charged insulator is placed near an uncharged neutral metallic conductor? I know it attracts each other because of charging by induction (electrons redistribute). But would the ...
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Expectation Value of the BCS Hamiltonian
I want to calculate the expectation value of the BCS Hamiltonian
$ H = \sum_k E(k) c_k^\dagger c_k - \frac{V}{2} \sum_{k,q} c_{k+q}^\dagger c_{-k-q}^\dagger c_{-k} c_k $
in the state $| \Psi \rangle = ...
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Would seawater flow be affected by a magnet?
Let's suppose that there are two streams of sea water, flowing on a flat inclined surface. Both of the streams are distant, independent of each other and parallel to each other.
Now lets image I put a ...
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What is the meaning of a conductor in equilibrium?
Electric field lines are always perpendicular to the surface of a conductor in equilibrium.
what is the meaning of a conductor in equilibrium?
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Understanding Kirchhoff's first law in charged conductors
I wonder about Kirchhoff's first law in charged conductors. Consider:
$$j = \sigma E \implies \nabla \cdot j = \sigma (\nabla \cdot E) = \frac{\sigma \rho}{\epsilon_0}$$
This means that Kirchhoff's ...
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Magnetostatics or dynamics?
A spherical conductor, carrying a total charge $Q$, spins uniformly and very rapidly about an axis coinciding with one of its diameters. In the diagrams given below, the equilibrium charge density on ...
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If $\vec{E}=0$ inside a conductor, then there's no charge distribution?
I got this answer to my last post,
See answer.
That raises another question, then. Knowing $\nabla\cdot\vec{E}=\frac{\rho}{\epsilon _0}$, then $\rho$ should be $0$ (because $\vec{E}=0$). But it's not, ...
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Will charges rearrange inside a conductor, or not?
I'm confused about how conductors work.
So, imagine we have a spherical conductor, charged with a certain potential, $V$, that must remain constant.
Now, this sphere has a cavity inside, where we put ...
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Gauss law at the surface of a conductor
I came up with a conclusion where I find half of the result on the picture.
Here is how can the half of the result:
I thought the same gaussian surface. But since we know that, charges outside the ...
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Electric field in a conductor and current flow
Consider a conducting wire which has some electrical resistance connected across a source of emf (voltage). Presumably there must be an electric field within the wire to cause the movement of ...
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Coaxial cylindrical conductors electric field in thickness of cylinders
So I want to calculate the electric field at all different locations for the two conductors in the image below.
These are two coaxial thin cylindrical conductors, that we assume to be perfect (so ...
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Electric field due to charge within a sphere
My question relates to the example given by Griffiths’ Electrodynamics regarding a sphere in a constant electric field.
Specifically, in Example 3.8 of Griffiths’ Electrodynamics, there is a metal ...
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Why is potential difference across resistor different than potential difference across a wire?
As far as I understand, the electric potential is the amount of energy that a third party agent has to spend to move a positive charge from infinite separation to a point. Thus, the electric potential ...
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Charged dielectric/conductor in capacitor
It is a standard problem to consider a dielectric or a conductor between the parallel plates of a capacitor. But what happens to capacity, voltage, charge, inserting between the plates of an ideal ...
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Confusion about Circuits
I have two questions:
When dealing with simple DC circuits, it is often said that the electrons in the wire move because the charge density of the surface charges decreases. Is that due to the fact ...
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Electric field in the hole of a conductor
My textbook has the following question:
A hollow charged conductor has a tiny hole cut into its surface. Show that the electric field in the hole is $ \sigma/2\epsilon_0$ $\hat{\mathbf{n}}$, where $\...
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What is resistivity? [closed]
What is actually resistivity?
I read that when the temperature increases the the resistance of the conductor increase. Length and area of a material doesn't change so it means that the resistivity of ...
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Question about Drude's model of conduction
Why is it proper to assume the electronic velocity after collision is zero in Drude's model?
(Where are momentum and energy conservation?)
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Perfect conductor and magnetic field
Inspired by this question.
Can current be induced in a superconductor?
Magnetic flux of a magnet cannot enter a perfect conductor. Again moving electrons, protons produce magnetic field (and thus ...
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Why does the dielectric current density operator is twice its value?
In second quantization, the time-independent Hamiltonian for free fermions is written as
$$\mathcal{H}_0=\sum_\sigma\int\mathrm d^3 \mathbf r\; \Psi^\dagger_\sigma(\mathbf r) \frac{\hat{P}^2}{2m } \...
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How can a current carrying conductor have $0$ electric field and be equipotential?
Consider a circuit with some resistance $R$ attached somewhere across a battery. The connection is made using some ideal conducting wires with $0$ resistance. Now, say some current $I$ flows through ...
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Electromagnetic fields in voltage biased conducting strip
Consider a conducting rectangular strip of length $L$ (along x-axis) and width $W$ (along y-axis), with a potential difference (rather EMF $\int E.dx$) V(t) applied. We can assume that V(t) changes ...
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How does a conductor in electrostatic equilibrium have no interior electric field?
Can't you construct a Gaussian surface small enough to surround only one of the interior protons, thus the surface has a charge enclosed and a electric field by Gauss's law.
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Physics of throwing a power cord into a swimming pool
I saw a few questions related to swimming pools so I figured out I may ask here.
If one takes a power cord that's plugged into a wall socket on one end and throws the other end in a bath, it may kill ...
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What will happen if we rub an insulator and conductor?
What will happen if we rub a neutral conductor with a neutral insulator? Will they get charged or remain neutral?
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Why more charges normally accumulate at the position with a larger curvature on a curved surface?
For a curved interface between two adjacent poorly conducting materials with different electrical properties, when applying a DC voltage difference between the two materials, as in a capacitor, the ...
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Why does current not decrease in/after a resistor if electrons are impeded/lose energy? [duplicate]
I was told that current is uniform across a series circuit. Yet I was also told that a resistor works by impeding the flow of free electrons, which should mean slowing them down. Does this mean that ...
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Temperature distribution in a current carrying conductor
A rod of uniform cross section and composition is connected across a battery. Let the middle part of the rod(when divided into three equal parts) is heated uniformly.
A book says that the temperature ...
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Why are lithium and beryllium such good conductors but not chlorine?
Why are lithium and beryllium so conductive? The $2s$ band has a much different energy range from the $2p$ band, so I guess the only explanation is that $N$ states are empty. But if that was the case, ...
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What is the most electrically conductive material at standard temperature and pressure?
Searching the internet, I find plenty of sources telling you the most conductive element is silver, and plenty of articles about potential room temperature superconducting alloys (none of which have ...
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Pn junction and the structure of diodes
I've read the part about pn-junction from Manfred Albach's "Elektrotechnik" book and I've seen some resources online as well. However, there are a few questions that bother me and prevent me ...
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