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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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Use the method of images to find the potential $V(r)$ in the cavity [on hold]

Here's a problem I'm stuck with. If the line charge is in the cylinder-shaped conductor, I'll know how to solve it by method of image.
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Induced charges in Electrostatics

How to find the distribution of induced charge on conductor kept in a uniform electric field? Is there a particular method to do the same?
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Non-Hermitian Hamiltonian for electron conductance in electric field?

Electron conductance in a solid state is usually driven by electric field - making some direction of jumps more likely. It makes (e.g. Hubbard's) Hamiltonian no longer self-adjoint, how to simulate ...
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When to use Poisson's equation in electrostatics

When does when elect to use Laplace's equation when dealing with charge distributions. For example, if I had a metallic sphere of radius $R$ and charge $Q$, then $$\mathbf E = \begin{cases} 0, & ...
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Thermal Energy in a Conductor

We know that thermal energy developed in a current-carrying resistor is given by $U=I^2Rt$ and also $U=VIt$. So my question is- Should we say that $U$ is proportional to $I$ or $I^2$
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Electric Fields 'passing' through conductor material

I've been reading Chapter 3.2 and 3.3 of Purcell's Electricity and Magnetism, 3rd ed, and found that I don't really understand a few ideas that Purcell makes about electric fields and conducting ...
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Gauss law electric field inside a conductor [closed]

Can you mathematically prove that if there is a cavity in a conductor and no charge is placed in it, the field at all points in the cavity will be zero?
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Prove: “If a cavity surrounded by conducting material is itself empty of charge, then the field within the cavity is zero.” [closed]

Prove: "If a cavity surrounded by conducting material is itself empty of charge, then the field within the cavity is zero." My attempt: Take a Gaussian surface that lies completely inside the cavity....
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Charge density on inner surface of conducting shell

The following exercise has brought to my mind something that confuses me: Here, I don't see why there isn't positive charge residing on the inner surface of the conductor at $r=a$. The way I see it,...
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37 views

When can charge reside on the inner surface of a conductor?

My confusion stems from the following exercise: I've written sloppily: "Why are charges not induced on at least that portion of the inner surface?". As I ask, I don't see how the charge density on ...
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Is the electric field within a cavity of a conductor affected only by other charges within the cavity?

The following exercise below confuses me: I don't understand why the answer is (A). I seem to be realizing empirically that the electric field at points inside a cavity in a conductor such as this is ...
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Plane of charge versus plane of charge on surface of conductor

The exercise below aiming to test my understanding has me confused: Why is the answer $(B)$? To me, I can envision for infinite planes of charge that its electric field lines are leaving normal to ...
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On the Electric Field of conductor under Electrostatic Conditions

Let us take a hollow conductor which has a charge Q uniformly distributed on its surface. Now, we know that the Electric field inside the conductor must be ZERO. But what happens when I bring ...
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How does charge develop inside a spherical shell (with non-negligible thickness)?

I read that if there were a charge $+q \ $ kept inside a spherical conducting shell of thickness $t$, a charge of $-q \ $ would develop on the inner surface of the shell. Not more, not less. Why is ...
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Why Electric field inside the spherical shell is zero? [duplicate]

electric field in and out of the spherical shell Why the field inside the conducting spherical shell is zero? Professor Lewin said and I quote," there is NO charge inside the conductor because any ...
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Why does electrostatic potential inside a conducting spherical shell seem to violate superposition principle?

I want to find the potential at the centre of a conducting spherical shell; The conducting shell bears a total charge of $Q$. The shell has a radius $R$, and there is a point charge of magnitude $q$ ...
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Why do 2 charged conductors gain same potential when connected via wire

Why do 2 charged conductors gain same potential when they are connected via a wire.Can somebody also give a mathematical proof of it?
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1answer
68 views

Point charge inside a hollow conductor, does the exterior field changes when the charge moves?

Suppose that I have a hollow conductor with no specific format. I know that if I put a charge inside it, it will induce charge in the inner surface and on the outer surface a charge with a opposite ...
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Is this a valid explanation for why charges in a conductor move to the outer surface?

This is a drawing of a spherical conductor with a hollow center. The black dots represent +ive charges, and the arrows represent their electric fields. I am assuming the black dots start on the inner ...
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Low energy electrons occupy holes

In Tipler's Physics it is said that for a temperature $T>0$ the only electrons that can gain energy from collisions are the ones with initial energy greater than $E_F-K_BT$. I understand that, ...
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Electroshielding in asymmetric conductors

Consider the textbook problem of a spherical conductor, with a concentric spherical cavity and a charge of +Q located in the center. By constructing a suitable Gaussian surface, we can deduce that the ...
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1answer
46 views

How can electrons travel from the valence band into the conduction band?

I'm currently studying Introductory Semiconductor Device Physics by Parker. In band-theory, we know that if an electron is at the top of an energy band, then there are no allowed states immediately ...
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1answer
156 views

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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Relation between potential and charge of a group of conductors

studying electrodynamics I encountered a few weeks ago this statement regarding a set of conductors in space with no free charges: I could not find an explicit proof of this in any book and I did not ...
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Does a conductor actively lose charge during electrical breakdown?

Electrical breakdown occurs when the potential difference between a conductor and the medium surrounding exceeds the breakdown voltage. In such scenario, the electric field at a boundary point is ...
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1answer
53 views

How can the surface of a conducting shell be equipotential when a charge is introduced inside the cavity?

Here is the confusion. Take a spherical conducting shell of a certain thickness. When a postive charge is introduced into the shell the inside surface collects negative charges and the outter ...
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1answer
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Why is the electric field between two conducting parallel plates not double what it actually is? [duplicate]

According to here: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elesht.html We can treat two parallel plates as being a single conductor which has an electric field of $\frac{\sigma}{\...
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Does a superconductor conduct electricity at room temperature?

I know you need to cool a superconductor below a certain temperature for it to exhibit superconductivity, but do superconductors, specifically YBCO superconductors, conduct electricity normally at ...
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How to (hypothetically) calculate $\tau$, the mean free time?

Referring to the Drude Model, I've seen a lot of excellent questions on whether $\tau$ should be thought of as the "average time between collisions" or the "average time until the next collision", and ...
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1answer
37 views

A Conducting Disc

A conducting disc is given a charge Q. As the disc is conducting it must be equipotential and hence the charge distribution will not be uniform. From what I know the charge will have a tendency to ...
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1answer
23 views

Electric potential inside a solid conducting sphere, next to other charges

The way I initially justified the potential inside a charged conductor to be $\frac{kQ}{R}\ for\ \ 0\le r\ <R$ was that from Gaus's law, you could determine that when you were a distance $r$ away ...
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1answer
22 views

Force between two point charges separated entirely by a conductor

The relative permittivity and hence absolute permittivity of a conductor is infinity. Now coulomb force between two point charges is inversely proportional to the permittivity of the medium between ...
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1answer
110 views

Induced charge in a conductor

My question here is based on the following question in Physics for Scientists and Engineers (3rd edition) by Randall Knight: An electroscope is positively charged by touching it with a positive ...
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93 views

What will happen when two conducting spheres are touched?

Suppose I have a conducting sphere with a charge of $$1.6 * 10^{-19} C. $$ What will happen when i touch this sphere with an identical neutral sphere? On which sphere will the charge reside?
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Existence of Electric field around a current carrying conductor? [duplicate]

A magnetic field could not be induced unless there is a time varying electric flux associated with the amperial loop under consideration. But a well known field exists around a current carrying ...
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1answer
51 views

Relativistic effect in a current carrying wire

In many places I read that in the rest frame of a current carrying wire (electrons in motion), the spacing between the positive ions is length contracted and equal to the length contracted spacing ...
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Why doesn't the flow electrons occur in a broken circuit?

Take a battery and connect a small led bulb across it with the help of two wires. The bulb will glow, but if I cut a small piece of wire from any part of the connecting wires,the circuit will not work ...
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Electric Field Inside of a Conductor [duplicate]

I have seen many explanations for why the net electric field inside of a conductor is zero (assuming only electrical forces are acting on the particles inside of it). These explanations typically say ...
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How electric current is defined in a metal wire?

How current is defined if in a metal wire both positive and negative charge exist? Isn't the total charge/time 0?
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Why some forces follow superposition principle?

Let there be a system of $n$ source charges and a test charge $Q$. When we say superposition applies to electrostatic force, we conclude that the interaction between a given source charge and the test ...
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1answer
40 views

Relation between Temperature and heat current

This problem: I was able to solve it doing this: But I think i have nowhere " exploited " the equivalence given above. How can this be used in this problem?
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59 views

The image charge inside the conducting sphere without producing any electric field [closed]

In the method of images for a grounded conducting sphere, we calculate the position of image charge at $$\frac{R^2}{r}$$, due to which there should be an electric field inside the conducting sphere ...
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Do conductors reflect Wifi signals? If so why?

I know electric field can't pass through conductors, but I have seen people surround their wifi router by soda can (not entirely) for better signal strength. I want to know what really happens there.
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1answer
107 views

Charge $Q$ in cavity inside conductor

A point charge Q is inside a cavity in an uncharged conductor. Is the force on Q necessarily zero? The explanation in the answer goes as No. For example, if it is very close to the wall, it will ...
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2answers
156 views

How far do electrons actually move along a conductor under an alternating current?

This is more or less a curiosity question. But I have had really good luck with stack exchange so far. If I can expand on my question a little bit - it may not be super important, but I know under say ...
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2answers
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Is it possible to become electrocuted even if using a Faraday suit on a high-voltage line?

I am a writer. I'm working on a novel (yes, fiction) but want to do my best to present a passage as accurately as possible. The crux of the question is whether or not someone using a Faraday suit ...
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3answers
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Do real electrons solve the Thomson Problem?

The question of how $N$ electrons (seen as point charges) on a conducting sphere will arrange themselves in the electrostatic final state was first posed by J.J. Thomson in 1904--hence, aka the ...
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Non-ohmic conductors

Non ohmic conductors are said to be the conductors that do not obey Ohm's Law. The V-I graph for them is not a straight line unlike ideal ohmic conductors. According to me Ohm's Law states: The ...
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139 views

Charge Distribution on a perfectly conducting hollow shell

As shown in the figure, I have a hollow shell which contains a charge at its centre and another charge is placed outside the shell (some distance apart). I know that the situation this figure depicts ...
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Why is there an accumulation of charges at the junction of 2 rods of different metals joined together?

Let two similar rods of different metals ( say copper and iron ) are joined together and some current is let to flow . Is there a charge accumulation at the junction? 1. If so what is the cause of it ...