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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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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What would happen to charge distribution when two charged, conducting spheres are placed in contact?

I have the following thought experiment. Assume that we have two conducting spheres. Sphere A has a charge of $+ 10 \ \text{C}$ and sphere B has a charge of $+ 8 \ \text{C}$. Now assume that we place ...
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EM energy flux and heat distribution in a cylindrical conductor

Consider a cylindrical conductor made of a single material (say, copper) with conductivity $\sigma$. Assume there is a current through the conductor and, to avoid complications, assume that the ...
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What is the meaning of a conductor in equilibrium?

Electric field lines are always perpendicular to the surface of a conductor in equilibrium. what is the meaning of a conductor in equilibrium?
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Does speed of electrons decreases when they pass through resistance?

What type of energy does battery supply to electrons , as I read battery increases KE of electrons but in load if they lose it then speed will decrease and current will decrease after coming out of ...
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Distribution of Charges on a Conducting Cup

A multiple-choice problem goes as follows: A small positively charged sphere is lowered by a nonconducting thread into a grounded metal cup without touching the inside surface of the cup, as shown ...
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How does the Lorentz force on a wire create macroscopic movement?

In a a current carrying wire exposed to a magnetic field, the electrons will experience a force and hence, a net displacement from. However it is not clear to me how this causes the wire to bend/move ...
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What does "grounded" conducting sphere placed in an initially uniform electric field mean? Why the resultant field change?

Consider this example of an electrostatic boundary value problem. Let an uncharged hollow conducting sphere of radius $R$ be placed in an initially uniform electric field, $\vec E=E_0\hat{z}$, along ...
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Why can't we use a slip ring instead of a split ring in a dc motor?

I've been taught that in a dc electric motor a split ring is used to connect the two ends of the rotating coil to two carbon brushes so that The wire does not get twisted and The current passing ...
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What happens inside a conducting wire if it is placed in an electric field?

what happens when you place a long Finite conducting wire in an Electric Field , does current flow through it ? Is Potential Same all over the wire ? i just got these questions in my mind as i was ...
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Seemingly easy Fleming's question, repeatedly getting wrong answer [closed]

Easy question deceived me and my budding physics ego😃. I solved the question in the following way: Took the field to be parallel to and opposite to the velocity of the electron as that was a fact ...
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Perfect conductor in a time-dependent magnetic field

I have read about how a perfect conductor responses to a time-dependent magnetic field. It was stated that the "equation of motion" of such a perfect conductor is given by $$\frac{dj(r, t)}{...
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Why do we use wires/conductors to transport energy?

I am currently studying Maxwell equations and I learned that copper wires are essentially just wave guides for EM waves. Why do we not use an insulator to guide the wave and transport the energy which ...
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Which charges pushes exactly a charge inside a conductor to the surface and why does it prefer curved surface?

I know this has a lot of questions about it, however my question is different: why does a charged particle inside a conductor get pushed toward the surface? The usual explanation is that in a ...
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What happens to the electric field lines in a high resistance conductor?

When a conductor is connected to a potential difference, an electric field occurs inside the conductor. We know in a high resistance conductor (for example a 20m long thin carbon rod connected to a 1....
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Do multiple current flows exists in a conductor? Does a slower current provide extra resistance?

If you have a running marathon with lots of people the slower people are in a sense an obstacle for the faster people behind them. The slower people create extra resistance. Is there an analogous ...
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Electric fields and intrinsic semiconductors

If we apply a electric field to a conductor the charges inside move close or away from the electric field which creates a electric field inside the conductor which cancels out the external electric ...
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Potential calculation in Electrostatic Shielding

I understand that in electrostatic shielding net charge present inside the cavity and the charge induced around it produce no net electric field in the outside region. Is this also valid for electric ...
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Non-zero total charge in a hollow conductor

Given a closed, hollow conductor (as understood in electrostatics), denote by $V$ its cavity. Let $$Q_V = \int_V \rho(x) \text{d}^3 x$$ be the total charge within the cavity. Is it always the case ...
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What does the electric field from a off-center charge inside of a metal sphere look like?

Consider a uncharged metallic sphere with a charge inside of it but not in the center, e.g. $0.5$radius upwards. What does this electric field look like? Without the sphere it is easily calculated but ...
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Does the space between field lines inside the conductor increase with distance and eventually disappear?

In practical scenarios where resistance is present, what happens to the electric field lines within a conductor? Practically, we say there is no flow of current in a high resistance conductor with a ...
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Vanishing electric field inside a conductor implies vanishing charge density but there is a puzzle

If we place a metallic conductor in a static, external electric field, the free electrons inside the conductor will move opposite to the external field leaving the immobile positive ions (nucleus+core ...
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Why is electric field zero in a wire with 0 resistance given nonzero voltage?

Why is electric field zero in a wire with 0 resistance given nonzero voltage and infinite charge inside a battery? It is true that for a wire with $0$ resistance there will uniform voltage across the ...
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How to measure water height thickness on infinitely flat surface with constant layer of water?

How would it be possible to measure layer of water on an infinitely flat surface, with every time different, but constant layer of water? I'm trying to measure thickness from $1\rm\,\mu m$ to $5\rm\, ...
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Method of averaging velocities of electron when deriving drift velocity

Here is derivation of drift velocity. Assume there is a field $\vec{E}$ inside the conductor(wire). Using equations of motion we can say that for every charge inside the conductor, $$\vec{v_1}=\vec{...
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What would happen on an atomic level to mercury in a microwave?

I'm not sure why I was thinking of this, but I did and I couldn't think of an equivalent physical model to relate microwaved liquid Mercury to. Polar substances are heated by dielectric heating, the ...
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On the definition of drift velocity in the context of Drude model

In Drude model we have $$\vec v_{\rm final} = \vec v_{\rm initial} + \dfrac {e\vec E}{m}t$$ here $\vec v_{\rm initial}$ is velocity just after some collision (so $\left( \vec{v}_{\rm inital} \right)_{\...
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Do you "lose" electricity when you course it through subpar conductors?

Imagine I had a basic circuit - say the classic 9V battery on one end, a couple of wires, and a little light bulb on the other. Of course, in a real world example those wires would probably be ...
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Centripetal force to charge carriers in curved conductors

Suppose we applied an emf across a circular conductor, then the electrons inside the conductors would drift to the positive side But how does the electrons get centripetal force? Firstly, I ...
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Understanding charge distribution conductors

Let's say that we have an uncharged spherical conductor. If we hold a charge +q near the conductor, then a charge distribution is induced. The positive charge q pulls negative charges over to the near ...
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Strength of the nucleus-electron interaction in the Kronig-Penney Model

The Kronig-Penney Model approximates the energy of an electron in a solid lattice as the following diagram: The region $0<x<a$ is the region where the electron is under the influence of a ...
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How to find the surface charge induced on a perfect conductor when Lorentz transforming electromagnetic fields?

Suppose that I have a perfect electrical conductor ($B=0$ inside conductor) in free space with a known magnetic field $\mathbf{B_s}$ outside of it, and no electric field. If I transform to a frame of ...
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Induced charge distribution in spherical simmetry

I've been trying to understand the following situation for a while now. It seems something so simple and easy and yet I can't find answers. Suppose we have a configuration like the one shown in the ...
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About parallel plate conductors' capacitance

Capacitance of the parallel plate conductors is $εA/d$ where $A$ is the area of each plate and $d$ is the distance between them. My question is, instead of 2 identical plates, what if we used 2 ...
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Phase transition in 1st and 2nd Order

I was going through some texts and they said that in the absence of magnetic field the transition of super-conducting material to and ordinary conductor is a 2nd order phase transition. It also said ...
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We know electric current is the flow of free electrons,but,where do these free electrons come from?how are they seperated from the valence shells? [duplicate]

We know that electric current is the flow of free electrons,these electrons have charge and they carry electrical energy and we use this energy to do work, alright,makes sense, but,from where do these ...
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What happens when you put a conductor inside a cavity, contaning a $B$ field, of another conductor?

My problem is this: A perfectly conducting material has a single cavity carved out inside it. The $B$ field in the cavity has the form $$B(r,t) = \text{Re } B_c(r) e^{-i\omega t}$$ and I've already ...
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Does it matter where you ground a polarized conductor?

my question is straightforward as the title says. I have a problem because my intuition is playing tricks on me I believe. Example number 1 is quite easy. There is an excess of electrons on the right ...
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Clarification about electric fields within conducting shells

If I were to have a conducting shell that has a charge of $+q$ on the shell itself, there would be no electric field inside the conducting shell itself as if I were to apply Gauss's Law to the inside, ...
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How is the electric field inside a hollow conducting sphere zero?

If we put a charge inside the cavity of a hollow conducting sphere, the charge will create an electric field and so the negative charges will move close to the cavity. This will create a shortage of ...
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Does current decrease with frequency increasing?

Electric field accelerates electrons in wire. Because of at least inertia, when the electric field (voltage) is applied, electrons will not instantly have some maximum speed, but will continuously ...
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Griffiths example 2.10 (conductor with a cavity) [closed]

The problem is related to a conductor with a cavity containing a charge $q$. Griffiths in the example states that the field generated by the induced charge $-q$ on the inner surface cancels out in ...
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If water is a bad conductor of heat (C=4200J per kg per K), why is it used as coolant/water cooling? :O

According to what I’m seeing, water is considered a bad conductor of heat. Colloquially, isn’t water supposed to conduct heat well as it’s used to transfer heat to a radiator, in everything form a pc ...
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Field outside a conductor with Cavity

I have a conductor with a cavity inside which a charge $q$ is kept now electrons inside the conductor will rearrange such that net electric field inside the conductor is zero, hence now using Guass ...
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Why will charge distribution be uniform on surface of conductor when we have a point charge inside a cavity in a conductor?

Consider this conductor By Gauss' Law and using the properties of conductor , I can certainly say that a $-Q$ charge will occur at the inner surface of cavity and a $+Q$ charge will occur at the ...
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