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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Mathematical proof that electric vector field in charged hollow conductive sphere is zero

I placed 250 evenly spaced identical positive charges Q=0.01 each (ignoring coulombs constant) around a hollow unit circle in mathematica and calculated the electric vector field: ...
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Electric field outside conductive surface with internal charge density

My professor told me that if you have a charge distribution $\rho \ne 0$ defined on a bounded region $V \subset \mathbb{R}^3$ whose boundary is a regular $2$-dimensional surface $\partial V= S$ which ...
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Why is the electric field between two equally charged conductors zero?

Two equally charged conductors of area $A$ and charge $Q$ are placed at a distance $a$ from each other. I want to calculate the electric field caused by the two conductors. I applied gauss law to each ...
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Why is current finite for point charges?

If an electron passes through a flat plane, then there will only be a single point in its entire path which lies on the plane,i.e the entire charge of an electron passes through in an instant (as it ...
1 vote
1 answer
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Conducting Sphere with a charge inside

What happens if we put a charge inside a conducting sphere(not a shell)? If we take a gaussian surface around the charge then we find that there should be charge at every radius of the sphere. But ...
10 votes
6 answers
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Why is the charge enclosed by a metallic conductive sphere zero?

The reasoning provided behind why the electric field inside a metallic conductive sphere is zero, in my textbook is - "In case of a metallic (conducting) sphere, the entire charge will reside on ...
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5 answers
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Apparent violation of Gauss Law

Consider the very long, current-carrying wire in the picture. On the left side in yellow, the wire has a very low resistance, that we will consider to be zero. But on the right hand side in green, the ...
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Equipotential surface

If we place a charge near a conducting sphere and the sphere isn't grounded since the opposite charge will get induced on nearer side and same sign (as of outer charge) charge will get induced on ...
3 votes
6 answers
476 views

How to understand electron drift velocity?

I know that electron drift velocity can be defined as $I$ = $nAve$, where $I$ is the electric current, $A$ is the cross-sectional area of a conductor, $v$ is the electron drift velocity in question, ...
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1 answer
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Two charged spheres connected by a wire and one is inside the other [closed]

Two charged spheres are connected by a wire, a small sphere is located inside a bigger one. Both spheres are charged and connected through a wire. The charge of the small sphere is 20µc and the charge ...
2 votes
1 answer
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Do electrons really move on the conductor?

For my understanding: Maxwell's equations combined with Poynting's theorem give us a model where electricity is energy carried along with the electromagnetic field (energy is stored in the field, not ...
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9 answers
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Can heat(?) flow from a cold object to hot object?

When we dip a spoon (stainless steel) into ice cream, does it becomes cold or stay the same temperature? If it does, can we say that heat(?) can flow from cold to hot objects? Is this the reason ...
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1 answer
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Charge accumulation on surface of solid sphere due to placement of dipole inside cavity

This is the case when a plus q charge is inside cavity (with same centre) of a spherical solid conductor. Everything is uniform. But what will it be like in second diagram I think the external ...
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1 answer
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Classic Image problem

The classic image problem: Here, to calculate the potential above an infinite grounded conducting plate and a point charge q held at distance d above the plate, the image method is used. Here, I want ...
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2 answers
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Does a perfect conductor has unlimited supply of charges?

In Griffiths, it has been written that A perfect conductor would be a material containing an unlimited supply of completely free charges. My question is, how is the unlimited supply of charges ...
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Explaining Valence Electrons

I want to explain the concept of free electrons in a conductor vs. an insulator as simple as possible for children that have not yet learned about valence electrons. Would it make sense if I explained ...
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Are there perfect conductors which do not display perfect diamagnetism?

A superconductor is a perfect diamagnet AND and a perfect conductor. Are there perfect conductors which are not perfect diamagnets ? Maybe topological insulators ?
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Plane wave in a finite conductor

I am questioning the validity of the standard formula for EM waves in conductors The standard treatment of EM waves in conductors are: $$\nabla \cdot \vec{E} = 0$$ $$\nabla \cdot \vec{B} = 0$$ $$\...
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What will happen if one electronic charge is given to a conductor?

I was taught in my physics class that if some charge is given to a conductor then the charge gets distributed over its entire surface. But what will happen if just an electron ( a point charge) was ...
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Questions about Maxwell capacitance matrix and reference point selection

Let's consider a system of n conductors. If I'm not mistaken, the Maxwell capacitance matrix tells us that the following system of equations applies: \begin{align} Q_1 &= C_{11}V_1 + C_{12}V_{12}...
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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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Gauss Law for finite linear conductor

Why can't Gauss Law be applied to a finite linear Conductor, while as the same can be applied to an infinite Conductor.
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Most Stable Orientation of Ellipsoidal Conductor in Electric Field

As described in the question title, say we have an ellipsoidal conductor where all three axes are of different length, and we place it in a uniform field. What is the orientation of the ellipsoid ...
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3 answers
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Non-zero electric field in an isolated conductor

I recently came across a problem in which a conducting rod was moving with constant velocity in a constant magnetic field, arrangement is such that rod, velocity, magnetic field are mutually ...
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1 answer
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Behavior of electrons in a resistor

Imagine a circuit with a constant voltage and no resistance. Every electron would gain the same kinetic energy as it moves from the negative to the positive terminal. If we add a resistor to the ...
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What happens if ONLY one terminal of a cell is connected to a piece of conducting wire?

I've learned that current will flow to bring the potential of both ends of a wire to the same value if there is a difference in potential between them. Consider a cell of emf, , and negligible ...
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Electric potential inside a polarised conductor

Say a conductor with an initial electric potential of zero is subject to an arbitrary charge. I understand that because if this outside charge, there would be charge distribution inside the conductor, ...
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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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1 answer
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Field within cavity of a conductor

The usual argument about the electric field being zero within the empty cavity of a conductor is as follows. Consider any two different points on the inner surface of the conductor. Let the first ...
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Is there a steady state for two conductors at different temperatures connected to a battery?

In order to understand better nonequilibrium statistical physics I came up with the following thought experiment. I wonder what are the requirements to obtain a steady state. Let us consider two ...
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Reasoning why the lightning shocks doesnt cause any shocks to a person inside car if the conditon is not fully electrostatic

I am just confirming here how the concept of electrostatic shielding helps in preventing lightining to be not getting into the car inside . So we know car has a metal body outside , so first consider ...
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Understanding the effect of gravity in the electric field inside the conductor

Purcell tells that for conductors in electrostatic condition with no charges inside the conductor , we might be tempted to say electric field should be zero. But he reasons that there might be other ...
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Matching conditions for perfect conductors in electro*dynamics*

I've been working through the problems on Wald's Advanced Classical Electromagnetism and recently I dealt with the scattering of a plane, circularly polarized wave off of a perfectly conducting ball (...
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Does potential inside a wire is different at different points?

When wire is connected to a battery with potential difference across the terminals of the battery 'V'. Now we know the potential difference accross the wire is also 'V'. My questions is do the ...
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Self-interaction energy of a chargeless conductor in uniform electric field

Say we have an uncharged, ungrounded conductor in a vacuum. We now turn on a uniform electric field that will rearrange the charges on the surface of the conductor, so that the potential inside (and ...
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Problem on thermal conductivity [closed]

I'm an highschooler who's very intrested in physics. I've stumbled on a problem on my textbook ("Dalla mela di Newton al bosone di Higgs volume III", or translated "From Newton's apple ...
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How will the current flow in the figure drawn below?

Consider the green material in the figure to be conducting. So, I was wondering how the current will flow in the rod, as the battery is not connected at the ends, but on the surface of the rod. Thus, ...
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Why is Fermi energy considered most probable energy that electron posses in solids?

It can be seen in graph that probability of electron occupying a energy level below $E_{f}$ is $>\frac{1}{2}$, then why it is said that Fermi energy is considered as most probable energy that ...
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Is the charge present only on the outer surface of a spherical conducting sphere or on both inner and outer surfaces?

Recently I was taught that in a conductor charge resides only on the surface of the conductor and the net charge inside a conductor is zero and so is the net electric field. But what if the conductor ...
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Why does an electric field "concentrate" along a wire?

I am studying EE and have (unfortunately) only found unsatisfactory answers to this question. Here is my understanding and confusion thus far. When a battery is connected to a wire, the electric field ...
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1 answer
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Intrinsic impedance inside a good conductor

I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following: Plane Waves in a General ...
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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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4 answers
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Why is current density in a conductor of uniform cross sectional area constant at all points?

According to what I was taught, if current was dispersed “uniformly,” current density would remain constant. So, in a conductor, the 'current density should be the same at all points.' But, given that ...
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Why is current same even if the area of the conductor differs?

Current is directly proportional to area if area of conductor increase Current increases but in tapering conductor area increases current remains same I have learned this equation I=enAv Where A is ...
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The second uniqueness theorem in electrostatics

Does the second uniqueness theorem just say that if there is an electric field that satisfies Gauss's law for a surface surrounding each conductor + a surface of elnclosing all the conductor, it is ...
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Conducting shell surronded by, dielectric shell, and an outside $q$ charge

I would like some help with my solution attempt. I have a conducting shell with radius $R1$, surronded by a dielectric shell with $\varepsilon_1$ and radius $R2$, and on the outside i have a $POINT$ $...
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Ohms law validity and EM waves in conductors

Ohms law, when $\sigma$ is real: $$\vec{J} = \sigma \vec{E}$$ Is derived from the steady state solution of the equation: $$m\frac{d\vec{v}}{dt} = e\vec{E} - \frac{m}{\tau}\vec{v}$$ Where $\vec{E}$ has ...
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Does charge always reside at the edge of a conductor's surface

Say I have a circular metal sheet with a charge $Q$ on it do the field lines come out from the edges alone or from across the entire sheet?
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Does microwaves nevertheless pass through smaller slits?

It is known that the Foucault currents prevent the microwaves to leave a microwave oven (MWO). The waves can not pass tru several times smaller openings than their wavelength because the grid of the ...
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Would a grounded copper heat sink located near a room's ceiling be an effective way to reduce a room's temperature?

I am thinking about a cheap but effective way to reduce the temperature of my bedroom in my apartment during hot summer nights. I live in an old apartment building and the air conditioner located in ...
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