# 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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### Why are 'low frequency' EM waves attenuated by a single layer of kitchen foil?

Can someone explain why my am radio doesn't work when covered by a layer of foil that is less than one 'skin depth' at the appropriate frequency? According to wikipedia and other websites on the ...
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### On proving the $E$-field is null inside the layer of a conductor having a cavity

Let us consider a conductor having a cavity (both can have an arbitrary shape) wherein a positive charge $+q\,$ is located: At the electrostatic equilibrium, the inner wall of the conductor will ...
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### A small size conductor causes a greater current in a circuit?

I have a question - let’s say I have a very small 2 wire cable connected to a load that draws a large amount of current, I’ve been told ( I have yet to do my own testing) that the smaller cable will ...
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### Can total charge be transferred from a conductor to another isolated conductor?

Suppose a conductor is charged (Total charge $Q$). Is there any method by which we can transfer the whole charge Q from the initial conductor to another uncharged isolated conductor? What another ...
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### What makes electrons 'more free or less free' to move around?

I understand that conductors allow electron flow because their valence electrons are 'free' to move around.. But what exactly determines this 'freeness' and the lack thereof that separates conductors ...
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### Is the electrostatic equilibrium that conductors reach a consequence of Coulomb's law?

We know that if charges were to be placed within a conductor, they would start to rearrange themselves until they reach an electrostatic equilibrium where all charges are 'still' and no $E$-field is ...
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### Do charged conductors exhibit an equipotential surface even when subject to an $E$-field?

A charged conductor, in the absence of an electric field, attains an electrostatic equilibrium such that its surface has a constant potential. When a neutral conductor is placed in a uniform electric ...
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### Why strong electric field leads to non-Ohmic behavior?

Homogenous conductors like silver or semiconductors like pure germanium or germanium containing impurities obey ohm's law within some range of electric field values. but if the field becomes too ...
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### What exactly does Ohm's law say?

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, R ...
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### On proving that charge is linearly proportional to potential for a conductor

In Mr. Purcell's Electricity and Magnetism, page 103, it is stated, An isolated conductor carrying a charge $Q$ has a certain potential $\phi _{0}$, with zero potential at infinity. $Q$ is ...
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### Is the $E$-field near and on the outer surface of a conductor null?

Let us say we have a conductor the outermost surface $S$ of which is given by $$S: \big(\,x(u,v),\, y(u,v),\, z(u,v)\,\big )$$ where $u$ and $v$ are parameters. Since it is a conductor, the ...
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### Movement of free electrons

How can I understand the movement of free electrons in a conductor taking into account the quantam mechanical approach of electrons i.e. uncertainty of position and momentum etc. Does using quantum ...
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### It is possible that without resistance current flow a conductor [closed]

It is possible that without resistance current flow a conductor (answer with proof by)
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### Why is it assumed that magnetic forces arising from magnetic fields do not do work on a current carrying conductor?

Imagine a long, thin current carrying conductor carrying a current $I$ and moving through space with a velocity $\mathbf v$. If there exists a magnetic field such that there is a force on the current ...
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### How fast does an electron move?

I've been reading this website: www.physics.wayne.edu/~apetrov/PHY2140/Lecture8.pdf to learn how fast an electron moves in a circuit. On page #8, #9 and #10 It says to take the Cross-sectional Area ...
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### Some confusion in Drude theory of metals

Discussion on the drude theory of metal usually begin with the case of zero magnetic field so that the force acting on the electrons is just the one from the electric field. But then, this electric ...
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### From where do electrons gain kinetic energy through a circuit?

Supposing an ideal wire, How do electrons accelerate and gain kinetic energy? What I understand: When a circuit is opened ,electrons are crowded at the negative term of the battery and have high ...
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### What exactly happens when a charged conductor comes into contact with an electric insulator?

Let us say we have a negatively charged conducting sphere: If we put an insulator into contact with the sphere: Would the negative charges located in the contact region transfer from the surface of ...
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### About fixing the potential on the surface of a conductor

In Purcell's Electricity and Magnetism, p.116 section 3.3, the author spoke about Laplace's equation and said that the boundary conditions for the potential$\,\phi$ on the surface of the conductor may ...
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### Why can't we have an $E$-field like this one inside a conductor?

From what I understand, there can be no $E$-field inside a conductor in an electrostatic situation, because had there been any field within it, the charges on the surface would start to move, thus ...
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### “Conductors having excess charge can attain static equilibrium”, is this an empirical law?

Is the redistribution of excess charge in a conductor onto its surface, thereby reaching static equilibrium (a steady state), only an empirical observation? Or, equivalently, is it guaranteed, i.e. ...
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### What is actually being removed when a metal conductor is grounded?

I found this image earlier this morning, and yes, there are a lot of diagrams/illustrations about this, transferring charges by induction has been introduced since the very beginning of high school ...
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### How does the electric field inside a conductor become zero? [duplicate]

When a conductor is placed in an external electric field, I know that the free electrons arrange themselves in such a way that the field inside the conductor due to these charges cancel the external ...
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### Electromagnetic field of a spinning cylinder

Let us consider an infinite cylinder of axis $(Oz)$ and radius $R$ spinning at a constant radial velocity $\omega$. We assume that this cylinder is made of a metal that is assumed to be a conductor (...
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### Charge on an electrical conductor

Consider we have very precise equipment (s) needed for this question. There's a finitely big uncharged conducting sphere. Suppose we had an extra electron from an external source and we plan to keep ...
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### What is the exact mechanism of flow of electricity?

When a steady current flows through a conductor, the electrons in it move with a certain average ‘drift speed’. One can calculate this drift speed of electrons for a typical copper wire carrying a ...
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### How do electrons lose their kinetic energy in ideal wire?

Electrons keep accelerating due to the electric field (produced by the battery) along the circuit. So electrons gain kinetic energy, hence their drift velocity changes. But this is not the case: ...
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### Why should the relation (current density)= (resistivity)×(velocity of charge) [$j = ρ v$] be applied to each type of charge carriers separately?

This is from the class 12 physics NCERT Part I. The relation $\mathbf{j} = \rho\mathbf{v}$ should be applied to each type of charge carriers eeparately. In a conducting wire, the total current ...
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### Relationship between Specific heat capacity and Electrical conductivity?

I am an IB student going into senior year and I have an Extended Essay to complete. The research question I formulated was "How does Electrical Conductivity depend on specific heat capacity?" So I was ...
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### Does a metal with a strong positive charge decrease its strength?

Does a metal with a strong positive charge decrease its strength? According to the mainstream theory of metal bonds, free electrons form a link between lattices. If this is the case, the removal of ...
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### Electric current and drift velocity

I have seen in several textbooks that say that when we connect a conductor with a battery then electrons start moving (drifting) in the battery in random up and down motion in the opposite direction ...
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### Electric field inside a conductor with an opening

Assume that we have a charged conductor of any shape but it has an opening so that we can get inside the conductor through that opening . Will the electric field be zero inside that conductor ? I ...
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### Charge distribution on a hollow conducting cube [closed]

Suppose we have a charged hollow conducting cube, will the charge be uniformly distributed over the surface of the cube? I know that the electric field will be zero everywhere inside the cube but to ...
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### Skin Effect Explanation

I do not understand some things about the Skin Effect. Its Wikipedia definition is: Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor ...
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### $E$ in a solid uniformly charged conductor: Is my reasoning here correct?

Suppose we take spherical conductor which is having both positive and negative charges but as a whole is electrically uncharged and is not under the influence of any external Electric field, We can ...
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### Is resistance determined by electron mobility?

How Is resistance determined by electron mobility for a given resistor or wire.
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### Potential due to initially uncharged induced conductor?

From Griffiths' Introduction to electrodynamics: In this problem, Griffiths says that we will set the potential inside and on the surface of the conductor to be zero since its an equipotential ...
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### How does charge movement vary between insulators and conductors?

I've been reading A Student's Guide to Maxwell's Equations by Daniel Fleisch, and he states: in nonconducting materials (called "insulators" or "dielectrics"), charge does not move freely, but may ...
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### Does electric field vary with cross sectional area in a non uniform current carrying conductor?

Suoppose I have a non uniform conductor which is kept in a uniform electric field maintaining a constant potential difference across its ends.Both electric field and current density are a properties ...
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### Which type of conductors don't follow Ohm's law? [closed]

Which type of conductors don't follow Ohm's law? I know that semiconductors and superconductors don't follow them, but why? And what about ideal conductors. What are they? Do they follow ohm's law? ...
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### How to find the charge distribution of a conducting disc?

Generally,Poisson's equation can be solved with appropriate boundary conditions to get potential from which the surface charge densities can be obtained. Most textbooks on Classical electrodynamics ...
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### Discrepancy in capacitor

Let a capacitor be connected to a battery in a circuit. The battery does work worth $CV^2$ but the capacitor stores only half that amount... We say the other half went away as heat, but how do we ...
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### Conductance Charged Box

A box with thick and conductive sides with dimensions: Lx, Ly, Lz- while LZ>>Lx,Ly. The long dimension of the box [Lz] can be viewed as infinite so Phi(x,y,z)=Phi(x,y) Given that: Phi(0,y)=-Phi(Lx,...
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### Negative real part AC conductivity

I am reading this paper, where the authors are calculating the frequency dependence of the chiral magnetic effect, i.e., ${\bf J} = \sigma^{\text{CME}}(\omega) {\bf B}$. The authors find, see for ...
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### How do surfaces charges accumulate?

When a voltage source is applied across an ideal wire, do the push of electric field of battery source causes the accumulation of charges on the surface of wire or the capacitance of wire causes it? ...
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### Why charges should go to the surface of conductor? [duplicate]

How can we show that charges should go to the surface of a conductor, assuming that system should minimize its energy? (With no additional assumptions and maybe using variation method!)
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### Why do electrons accumulate on the surface of a wire (along its length) when a voltage source is applied across the wire cross section?

When I was going through how electric fields are transmitted long distances through a wire, I read that there was accumulation of charges along the surface of the conductor to drive the fields to long ...
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### Electric field inside and outside a hollow spherical shell

If a charge(+q) is placed at distance away from a hollow spherical conducting shell , would the net electric field inside the hollow portion remain zero? If the +q charge was placed anywhere inside ...
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 ...