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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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A question about resistivity ( high school physics ) [duplicate]

Resistivity = (Resistance times area ) divided by length $$\rho = (RA)/l$$ now my question is that in order to calculate the resistivity for some metal we have to take into account its length and ...
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0answers
92 views

Confused about the Drude model

I was thinking about the Hall conductivity, when this question popped up. If there is a magnetic field and an electric field perpendicular to it, then a Hall current is generated since the ions have ...
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1answer
42 views

Why does a tree branch under high voltage not stop conducting?

When a tree branch touches a high voltage power line, the first result is typically a small arc at the touching point at first, and then, for some time, vapor emerging from the point of contact, and ...
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2answers
59 views

Current in a conductor

In electrostatic shielding, we have read that the charged particles in a conductor experience no force. In the current carrying conductor, electric field is applied across its ends and the ...
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126 views

Relation of carrier density to number of valence electrons in metals

In the classical Drude model, we find that the electrical conductivity of a metal is given by $$\sigma = \frac{ne^2\tau}{m} $$ where $\tau$ is the relaxation time, $m$ is the electron mass and $n$ is ...
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6answers
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Speed of electrons in a current-carrying metallic wire: does it even make sense?

Does it make sense to speak about the speed of electrons in a current-carrying wire (non perfect conductor)? If so, what is their speed? Here are my thoughts: On the Internet (Wikipedia, ...
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1answer
147 views

What is the name of metal-metal junction?

When two different metals come in contact, a junction at their contact is created. What is the name of that junction?
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2answers
69 views

Is there a theory of electrostatics in the presence of conductors with finite conductivity?

A substantial part of my university EM course was devoted to the study of conductors in the presence of static electric fields. Poisson and Laplace equations were covered, along with the uniqueness ...
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1answer
53 views

Charge distribution in conductor

Here are two common statements about the charge distribution in a solid conductor: There is no net charge inside the conductor, "because if we think of charges as balls repelling each other they will ...
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2answers
245 views

The consequence of electric field lines not being perpendicular to conductor (assuming a spherical one)

The following statement is from University Physics (chapter "Electric Potential"): "In particular, at any point just inside the surface the component of E vector tangent to the surface is zero. It ...
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3answers
2k views

Is current the speed of the electrons?

My teacher got me really confused this time. He said that current is the rate of flow of charge. If this is true, then current could be the speed of the flow of charge (ie. the kinetic energy of the ...
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1answer
50 views

Inconsistency when Applying Gauss' Law

I'm using two methods to calculate the net electric field a certain distance away from the conductor. In the first method, I let the Gaussian cylinder go completely through the conductor and did the ...
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4answers
30k views

Why can I touch aluminum foil in the oven and not get burned?

I cook frequently with aluminum foil as a cover in the oven. When it's time to remove the foil and cook uncovered, I find I can handle it with my bare hands, and it's barely warm. What are the ...
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1answer
38 views

Is the speed at which electrons move through a conducting wire binary?

If a voltage differential causes electrons to move through a conducting wire, and no other forces are acting against them, will they always move at the highest possible speed through that material? ...
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1answer
98 views

Best visualization of electric current and voltage

I asked this exact question on the electrical engineering stack exchange, and it was suggested that I post it here: So, I want to know what the best way to visualize what is actually happening in a ...
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1answer
150 views

Electric current in anisotropic media

I'm trying to model a bulk metal with anisotropic electrical conductivity such as graphite. I want to run a stationary current through the material and I am using the finite volume method to do this. ...
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2answers
64 views

Does a battery actually provide electrons or are they the electrons in the wire moving due to potential difference?

When we connect a battery in an electric circuit, does it provide the electrons present at anode, or are they the electrons present in the wire?
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3answers
271 views

Can electric field lines from another source penetrate an insulating hollow shell which is uniformly charged?

There's a hollow insulating sphere that is uniformly charged with charge $Q$ kept in front of a big insulating square plate uniformly charged with charge per unit area sigma kept in $y$-$z$ plane. The ...
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1answer
611 views

Force on a charge placed in conducting shell

I have a very different theoretical physics question. Suppose we place a positive charge inside a conducting shell(not at the centre and not fixed), it induces the negative charge inside the shell. ...
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1answer
247 views

How do electrons actually move in a wire? [duplicate]

Do they jump from atom to atom or are they free-flowing? Where does resistance fit in? Do electrons physically HIT the atoms? If so, how do they hit atoms if the nucleus is small and far away from the ...
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2answers
457 views

Quantum mechanical interpretation of resistance and voltage drop

It is generally said that Ohm's law isn't a real law since it is only a fine model found through experiments to explain the nature of circuits. And resistance is defined as the ratio of the voltage ...
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2answers
500 views

Does a grounded conductor have zero charge?

If a charged conductor is connected to ground, does that mean that along with the potential of the conductor being zero, the charge on it is also zero as soon as it is connected to ground?
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1answer
133 views

Can four probe method be used to find resistivity of metals?

Can we use four probe method to find resistivity of metal/conductor. I searched the question on google, but could not find the answer. My guess is that we can use. Why not?
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1answer
50 views

The voltage on unclosed conductor

There are an unclosed conductor, and two magnets that situated, as shown on the picture. Is there voltage between conductor's ends?
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1answer
539 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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1answer
246 views

Modified Coulomb's law (hypothetical) and conductor

I came with problem where it was asked to comment on the charge distribution and electric field inside a solid conductor sphere, if the Coulomb's, instead of following inverse square relationship, ...
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2answers
604 views

Why does Griffiths's book say that there can be no surface current since this would require an infinite electric field for an incident wave?

In sec. 9.4.2 Griffiths shows the well known boundary conditions for E and B fields, one of them is this: $$\frac{1}{\mu_{1}}\textbf{B}_{1}^{\parallel}-\frac{1}{\mu_{2}}\textbf{B}_{2}^{\parallel}=\...
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1answer
62 views

Heat that we feel [duplicate]

I have just came across a site saying that when we touch a good conductor and if it's temperature is a lower than our body we feel it cold as heat starts flowing from our hands to it. On the other ...
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1answer
30 views

Is there twice the amount of current in semiconductors than that in conductors (at same temp.)?

In semiconductors unlike conductors where $e^-$ move from lower quantum states to higher quantum states in conduction band, electrons move from Valence Band to CB and create 'holes'. These holes add ...
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2answers
58 views

Current in semidconductors

I'm confused as to why when we measure current in an intrinsic semiconductor we calculate the summation of the current due to holes and that due to electrons as opposed to what's done in conductors. ...
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2answers
117 views

There is no electric field in a metal if the current through the conductor remains constant.

In a chapter of superconductor, I found, "There is no electric field in a metal if the current through the conductor remains constant". My question is, "Why the electric field is zero in such case?". ...
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0answers
318 views

How to prove that the induced surface charge on a conductor is univocally determined?

Suppose we have a conductor $\Omega$ and a charge distribution $\rho$ outside said conductor in free space. Elementary electrostatics tells us that $\rho$ will cause the free charges inside $\Omega$ ...
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2answers
641 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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1answer
22 views

What photoconducting materials/metamaterials reach full conductivity within 1/30th of a picosecond

I'm doing research on photoconducting materials/metamaterials but I'm having a hard time finding confirming how fast they reach full conuctivity, What photoconductors reach full conductivity and back ...
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1answer
352 views

Infinite conductor plane near a point charge

If i have an infinite conductor plane near a point charge ( that is the configuration of the common "Method of images" example), if i calculate the conductor's inducted charged density as $$\sigma =-\...
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3answers
289 views

Why is the electric field across a perfect wire zero?

I’ve looked at the answers given to the previous times this question has been asked, but I still don’t seem to understand how this holds in the case of a closed circuit. Here’s an explanation given ...
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1answer
540 views

The charge surface distribution of a conductor with a non centered charge

A point like charge Q is placed inside the cavity of a spherical conductor of an internal radius R1 and external radius R2 initially neutral(uncharged) (see the figure), the question is how is the ...
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1answer
96 views

Electrons close to Fermi-Conductivity

As a student of electrical and computer engineering solid state physics is not my thing so I might have fundamental blanks here and there. I really like this course and I try to gain as much as ...
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1answer
169 views

Why the electric field inside a capacitor isn't nul?

I have a doubt regarding this point, i know that the electric field inside a conductor is null, and the capacitor is made by two conducting plates, so what s the point here?
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1answer
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Can you conduct electricity through a banana peel?

While grabbing a banana for breakfast today I got zapped due to static electricity building up while I was moving on my chair, but the conductor I was grabbing was said banana. Is it possible to ...
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1answer
371 views

A point charge near an infinite conducting plane

I want to calculate (with Poisson's equation) the electric field in the region containing a point charge near an infinite conducting plane with 0 potential. My textbook uses V(x,y,z)= 0 for every x,y,...
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1answer
62 views

Replacing an equipotential surface with a conductor

If i replace an equipotential surface generated by a charge distribution with a conductor (i already know that the conductor has an equipotential surface), what assures me that the original charge ...
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3answers
5k views

Tree vs lightning rod: why does one burn and the other not?

I have this simple question, but I cannot find the answer. I saw this video about a plane getting hit by lightning. In it, Captain Joe explains why people do not get electrocuted. This has a simple ...
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2answers
252 views

Ohm's Law in a conductor

Assume steady-state conditions and a homogeneous conductor. Then dp/dt = 0 where p is volume the charge density. If ohm's law apply in the conductor, then $${\rm div}\ \bar{J} = {\rm div}\ \bar{E} = ...
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1answer
47 views

Point resistance

The resistance of a given object is expressed through: $$R=\rho\frac{l}{A}$$ I'm wondering if there is any quantity like resistance at a specific point. For example, $R$ for a copper wire with l=...
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2answers
615 views

Electric field below conducting plane

In Griffiths introduction to Electrodynamics, the classic image problem is presented: There is a charge $q$, above a grounded conducting plane. Griffith says that the electric field below the plane is ...
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2answers
420 views

Charge distribution in a hollow sphere [duplicate]

In electrostatics, why in the internal surface of a hollow charged sphere there aren't charges?
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1answer
65 views

Entropy in Conductors

In Introduction to Electrodynamics by Griffiths, it is given that Like any other free dynamical system, the charge on the conductor will seek the configuration that minimises its potential energy. ...
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0answers
482 views

Semiconductors vs. Metals Conductivity at High Temperatures

For metals, I've been told that as temperature increases it's resistance increases, due to the lattice vibrating more, and thus there are more collisions with electrons (increasing resistance). ...
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3answers
188 views

Is it possible for a conductor to run out of free electrons?

For example, imagine I apply a high voltage to a piece of conductor (copper) and make the electrons jump out of it like a automotive spark plug. Can the copper after a prolonged period of time run out ...