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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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Doubts on conductor and insulator

I read on Stephen Gray's discovery of conductor and insulator. From that I came across a question that how cork, wood, rope can act as conductor being an insulator but then I got the answer that it is ...
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Why doesn't shell theorem work here?

I think I have a misunderstanding about the shell theorem regarding electrostatics here. Since we have a conducting spherical shell, and we are looking for the $E$ field, shouldn't it be 0 within ...
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Why Electrical conductivity tensor is symmetric? Or is it not always symmetric?

How to show that the electrical conductivity tensor is symmetric? (or it's not always symmetric?)
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Equipotentiality of the conductor surface with extra charges sprinkled and Poisson's equation

The electrostatic potential $\phi(x,y,z)$ everywhere on the surface of a conductor/metal is the same. For a quick reference see this post. Hence, any derivative of $\phi(x,y,z)$ must be zero on the ...
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Is it possible to use Ampere's law to calculate vector B around short straight line conductor?

Maybe this question sounds easy, but I would really be grateful if someone could give me an explanation if it's true or not. I'm not sure if I understand it good enough.
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1answer
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Confusion in least action in the following situation

I understand that when electric field is applied normal to the surface of a conductor the net electric field inside the conductor is zero. But as shown in the diagram above, if electric field is not ...
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How does electric current continue to flow in a circuit despite there being zero potential difference?

Consider a conductor connected to a battery by conducting wires. When wires are connected then after a very small amount of time steady state is achieved and voltage across conductor becomes equal to ...
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Why can't free electron flow in water to conduct electricity?

This question is related to how batteries work. In a battery, the electrons can only flow in conductors, because they can't flow in the solution. my own thoughts on the matter: I believe it is ...
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130 views

How to show that the electrons responsible for a current have an energy within $k_BT$ of the Fermi energy?

It is commonly written in textbooks that in metals the electrons responsible for an electric current are the ones that have an energy about $E_F$ and a few $k_BT$ around that energy. See for example ...
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1answer
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Is electric force constant all over the surface of a conductor?

This question was asked in IIT JEE 2010. I know that the electrostatic pressure is equal to (1/2)∈(E)² and if we multiply this with the projected area then we would get the force acting on an object ...
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Why should there be electrostatic equilibrium inside a conductor? [duplicate]

I have been trying to understand why the net electric field inside a conductor is zero regardless of the exterbal electric field. But why should equilibrium ever be attained?
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Hydrogen: Whether it's a metal or non-metal

I know hydrogen is a non metal, but when I just study about some introductory elementary band theory I find the band structure of hydrogen has a half filled valence band just like alkali metals, and ...
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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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1answer
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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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2answers
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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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1answer
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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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1answer
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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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93 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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1answer
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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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179 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
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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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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
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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
32 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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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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120 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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109 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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3answers
85 views

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 ...