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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6answers
109 views

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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3answers
91 views

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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1answer
30 views

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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2answers
472 views

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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1answer
44 views

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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1answer
215 views

Coaxial cable with compound dielectric

I'm trying to solve a problem from Reitz and Milford's Foundations of Electromagnetic Theory (3rd ed, problem 4-8), and don't know how to start: A coaxial cable of circular cross section has a ...
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1answer
18 views

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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1answer
191 views

Earth as a conductor

In a lightning rod or other safety devices, charge is directed towards the earth. How the surface of the earth can be used as a conducting path despite being composed of material that is not a good ...
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2answers
759 views

How do I apply Gauss's law to coaxial conducting cylinders?

$$ \vert \vec E\vert =\frac{\lambda}{2\pi \varepsilon_0 r} $$ So I know this is the magnitude of the electric field of a line of charge using a cylindrical Gaussian surface. But, now let's say I have ...
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2answers
405 views

Is there a way to make infrared pass through metals?

I am curious to know a way that will make infrared pass through metals. Metals are good reflectors of infrared,can we manipulate the wave in order to make them pass through metals?.
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1answer
56 views

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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0answers
29 views

“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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3answers
516 views

Do charges move to the outer surface of a conductor to minimize the potential energy?

We can think the charges go to the outer surface of a conductor to minimize the electrostatic potential energy of the system. We can check this using a simple calculation using a charged sphere. A ...
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1answer
238 views

Difference between bound and free charge/current in a perfect conductor

For the case of charge, it seems clear that in a perfect conductor the free charge refers to the excess charge that has been dumped into the conductor, while the bound charge refers to the charge that ...
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1answer
569 views

How do insulators lose their charge?

Some theoretical questions that got me confused during physics lecture today. bringing a conducting balloon to a negatively charged rod close will allow the conducting balloon have positive charges ...
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2answers
579 views

Charged dieletric/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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2answers
1k views

Why can an insulator send charges to a conductor via conduction, and not upon an insulator via conduction?

Suppose we have an ebonite rod (insulator). This rod has a negative charge, and once it touches a neutral pith ball, charges are distributed amongst the pith ball. However, why doesn't the same happen ...
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2answers
47 views

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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0answers
42 views

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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1answer
134 views

Is this the correct voltage graph of a conducting sphere in the presence of another charge?

This grading rubric show an example of an acceptable answer, however I wonder if the slopes at the surface of the second sphere are wrong. This is a previous AP Physics test question so I'm inclined ...
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1answer
21 views

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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1answer
9 views

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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2answers
403 views

Why doesn't a conductor between two wires affect the current wires?

When an aluminum plate is placed between two wires (lying parallel to each other), it doesn't change the repelling nor attracting force between the wires when a current is passing through them. But ...
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2answers
53 views

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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1answer
54 views

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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1answer
65 views

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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1answer
143 views

Gauss' Law and Electric Field Close to a Ball

So I've learned about Gauss' law and I have something in my head. Why does electric field that is very close to a ball is not close to infinity. Take a look at this image: As we can see, if we make a ...
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2answers
101 views

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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1answer
121 views

Surface charge on a resistive wire in DC circuit

I want to understand how does the energy transfered from battery to the resistor in a simple dc circuit . I read that it is due to the surface charge the battery creates on the wire. So why this ...
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1answer
41 views

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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0answers
28 views

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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2answers
46 views

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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0answers
132 views

Redfield quantum master equation

In the framework of Redfield Quantum Master Equation, the popular approach is to use a tight-binding model linear conductor for the modeling of the Fermionic bath. Does someone can refer me to more ...
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1answer
24 views

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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2answers
266 views

Electrostatics and electric field inside conductor

I have tried for a while finding an answer to this question. Similar ones have been explained earlier by using Gauss law. However I am wondering about the physical change happening to the conductor in ...
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1answer
133 views

How is the $E$-field getting canceled between outer and inner surface of a neutral conducting spherical shell?

I am reading Purcell's E&M book and in one of the example questions, it shows that there is no E field between outer and inner surface after a a point charge is located at an arbitrary position ...
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0answers
35 views

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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1answer
67 views

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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1answer
28 views

$E$ 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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1answer
75 views

Is resistance determined by electron mobility?

How Is resistance determined by electron mobility for a given resistor or wire.
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5answers
9k views

How does a wire carry alternating current?

Consider a simple network of a bulb whose two terminals are connected to two wires with open ends A and B respectively A o--------💡--------o B Now if a DC ...
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1answer
22 views

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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1answer
31 views

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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5answers
129 views

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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0answers
56 views

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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2answers
46 views

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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0answers
33 views

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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1answer
54 views

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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0answers
22 views

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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5answers
682 views

Hollow conductor containing charge: why is internal field cancelled outside and why are the field oustide the cavity zero inside the cavity?

I've a doubt on the following situation. Consider a hollow conductor $A$ (of arbitrary shape) containing another conductor $B$ (again of arbitrary shape), with a positive charge $+q$. By the ...