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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42 views

Due to the movement of charge inside a cavity in a spherical or random shell, the charge on the outer surface of the body does not change. Why?

I have read the same in many textbooks. What's happening inside the cavity does not have anything to do with the surface charge. But I am not understanding the reason for this.
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How do you calculate the reflectivity of material from its conductivity?

How do you calculate the reflectivity of material from its conductivity? For example, gold at v=9x10^12/s (this problem is from the electronic property of material by Hummel). Is it possible to use '...
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1answer
59 views

Why does London equation not hold for normal conductors?

In exercise 13.2 from Fetter, Walecka - Quantum Theory of Many-Particles Systems it is asked to obtain London equation as the Euler-Lagrange equation for the Helmholtz free energy and to discuss its ...
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1answer
24 views

Joining two insulators at different potentials with a conductor

If two insulators are connected by a conducting wire, will the charges flow if they are different potentials? According to me, as the charges can't enter the insulators, charges only get distributed ...
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Find the frequency range for which sea water is good conductor [closed]

if sea water has conductivity = 4 mho/m and permittivity = 9*10-9/4*3.14 F/m find the frequency range for which sea water is good conductor.
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Does crystallized silver conduct electricity better than amorphous silver?

Silver conducts electricity the best of all the common metals and metallic compounds. Is there any advantage to using crystallized silver as a conductor? Do crystals of silver conduct better than ...
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3answers
53 views

Why is the charge distribution on the outer surface of a hollow conducting sphere uniform and independent of the charge placed inside it?

There is positive charge inside the hollow conducting sphere, closer to the left edge of the sphere. It attracts more electrons on the left, than on the right. What I can't get is why is the charge ...
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3answers
61 views

How is energy really dissipated in an electric circuit?

I've heard that in a circuit, energy is provided to separate components (lamps, motors, etc.) because of the flow of electrons. How is this possible? Since energy cannot be created, where is this ...
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2answers
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How does a current cause a voltage?

In most textbooks I've read, the explanation of Ohm's Law begins by assuming that there is an external voltage applied to a resistive (Ohmic) device. From there, it is explained that this voltage ...
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1answer
74 views

Transient heat conductivity with variable heat flux in 1D

I have a metallic block heated by a heat flux variable in time on one of its faces (let's assume that it is infinite in the other dimensions). I would like to compute the temperature over time at a ...
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1answer
39 views

What is the microscopic explanation for why is there more power in a circuit with a smaller resistance?

According to the Drude Model of electron flow in a circuit, the drift velocity is inversely proportional to the resistivity. $$E=\rho J$$ $$E=\rho Nev_d$$ $$E=\frac{-\rho Ne^2E}{m}\tau $$ $$\rho=\...
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What material should I use for the plates of my homemade mica capacitors?

I recently acquired some mica as i want to build my own high voltage (50 kV if possible) capacitors. The problem I am encountering right now is that the surface of such a crystal isn't perfectly flat ...
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4answers
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Do electrons deccelerate through a resistor?

In a circle the voltage drops across a resistor. This means that some electrons lost some of their electrostatic potential energy. Where does that energy go, and how? For potential energy to be lost ...
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245 views

Why do the charges on a parallel plate capacitor lie only on the inner surface?

In most pictures I've seen of parallel plate capacitors, charges are drawn so that they're entirely on the inner surface of the plates. I accept that there can't be any net charge within the ...
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1answer
27 views

Conductor as an Equipotential; Mathematically

I understand that every charged conductor is an equipotential, with electric field zero inside the conductor, and all excess charge on the surface of the conductor. I am a bit confused as to how the ...
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1answer
28 views

How can one show that scattering time scales with temperature as

Drude's law $\sigma=\frac{ne^2\tau}{m}$ involves the scattering time $\tau$, which, as mentioned in this short article, at low temperatures typically scales as $\tau\propto T^{-2}$. The author states ...
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1answer
65 views

Charge inside a cavity in a conductor

My teacher told that when a charge is placed inside an arbitrarily shaped cavity in a spherical conductor, the charge occurring on the outer surface is distributed uniformly, and this will imply that ...
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1answer
34 views

When AC electricity is generated, how does the current flow? [duplicate]

I have read multiple different versions of how AC current flows in our power lines. How does the current flow? Is the energy just photonics waves passing through electrons that vibrate or are ...
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35 views

Resistance in special cases

I am curious- I know that resistance doubles when length does, and that resistance would be halved if cross sectional area was doubled - But is there such a case of special conditions where It ...
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2answers
33 views

A doubt regarding a metal ball in an uniform electric field

This is a question from Griffiths, the details of which have been mentioned in the figure itself. What I am not being able to understand is, why should the potential on the xy plane be zero? If I ...
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36 views

Why is electric field between concentric spherical conductors NOT zero?

In studying electrostatics i learned that the electric field inside a conductor with no charge on the inside is always zero. I understand why this is, and i understand that no stable configuration of ...
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1answer
40 views

Why is the graph (Voltage vs Current) of an ohmic object not exactly linear?

What are the reasons for the graph Voltage vs Current of an Ohmic object being approximately and not exactly linear? In other words, we accept its lineality, but in reality, it is not exactly linear. ...
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3answers
159 views

How is the uniqueness theorem is used in this example?

I was going through example 2.10 in Griffiths(Introduction to Electrodynamics 4th edition), everything seemed okay, but at last he makes an assertion, the proof for which I am not able to understand. ...
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Electrical conductivity and the limits of Kohlrauschs law

I am currently writing a lab report on electical conductance and i realised that my partner prepared $0.1$M solutions instead of $0.01$M. Now, i am supposed to find the molar conductivity at infinite ...
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1answer
24 views

Can a point charge inside spherical shell conductor with non negligible thickness experience forces from other charges outside the conductor?

The title says all about the subject matter. Can a point charge stationed inside a spherical shell with non negligible thickness experience forces from other charges outside the conductor?
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2answers
93 views

Distribution of charges on the surface of a charged conductor

It’s said that any excess charge inside a conductor will redistribute at it’s surface. Now there are two cases to it:- 1) A neutral conductor placed in an electric field 2) A charged conductor kept ...
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1answer
65 views

Research that explains why it‘s fine to microwave a spoon but not a fork

I‘ve found plenty of articles explaining this and understand that it has to do with voltage differences at sharp corners of the object, but could find no direct research sources. Does someone know a ...
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35 views

Electric field in conductors [closed]

How would you prove mathematically that electric field inside a conductor is zero? I know the arguments but I am looking for a mathematical proof for the same.
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1answer
52 views

Electric charges under electric field and discharge in wire

Assuming that we have two plates providing very strong electric fields. Two wires are held close to them to induce charges in the wires. Assuming that an empty capacitor is charged with the charges ...
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1answer
25 views

No electric field inside a conductor

In the existence of an electric field, the free electrons start drifting ,thus creating an opposition field, which keeps growing as more electrons start drifting. When this opposition field becomes ...
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1answer
24 views

Electric field inside a curved conductor

Consider an electrical conductor in the shape of a parabola (or any other curve) connected to the ends of a dc power supply such as a battery. The electric field inside the wire at any point is ...
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1answer
69 views

How does electricity work exactly? [closed]

So it just isn't popping for me how electricity actually works. AC at 60 Hz can swap directions 60 times a second and drift at roughly 1 m/s while they kind of ping pong forward with constant push ...
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24 views

Electric field at the surface of a conductor

Elecric field near the surface of a conductor is $$E= \frac{\sigma}{\epsilon_0}.$$ What is instead the electric field on the surface itself of the conductor? Just inside the surface, in the ...
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2answers
73 views

What is meant by the resistance that is provided by conductors?

When we talk about electricity we say that flowing electrons experience resistance by the lattice atoms. But how do lattice atoms provide resistance? They have their shell, their electrons, and their ...
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24 views

Is capacitance of conductor an Intensive property?

Capacitance is the ability of a conductor to store a charge. Capacitance is always told to be similar to water tank. Capacitance can't be changed by presence of other charges. But at the same time ...
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14 views

Charge distribution and potential changes on earthing for conductors placed close to each other?

Suppose we have two conducting plates with charges $2Q$ and $3Q$ placed close to each other (ignore edge effects for simplicity). It is clear that when the switch is open, the charge distribution is ...
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79 views

Dipole moment of conducting sphere in uniform electric field

As stated in the title, uniform $E$-field generates dipole moment. $$\vec p=4πε_0R^3\vec E.$$ One way to show this is considering the following configuration: two spheres with radius R with uniform ...
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1answer
77 views

Can metal or carbon vapour conduct electricity?

Not a duplicate of Can Gases conduct Electricity, since it asks about ionised gases, which is irrelevant to my question. This is what I already know: All metals have a giant metal lattice, where ...
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3answers
65 views

Electromagnetic waves in a conductor

I am trying to understand the solution for electromagnetic plane waves in a conductor. I understand the derivation of the wave equation: $$\nabla^2 \boldsymbol{\mathrm{E}} = \mu\epsilon \frac{\...
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2answers
59 views

Conduction Theory [closed]

Why the conductivity of Metal increase with a decrease in temperature, semiconductor increase with an increase in temperature and alloys remains the same ? Is it due to the following reasons? ...
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54 views

Charge inside a charged hollow conducting sphere with a hole

How are the following results theoretically explained? As part of an electrostatics exercise we were to measure the charge on the outside and inside surfaces of a charged hollow conducting sphere ...
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1answer
43 views

Supposed charge distribution on a metallic sphere

Usually when we talk about charge distribution on a sphere we say that excess charge resides on the surface of metallic sphere. As is said here: The net electric charge of a conductor resides ...
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3answers
119 views

Why do charges uniformly distribute themselves on the surface of a conducting sphere with a charge inside its cavity?

If we move the charge $+Q$ a little bit to the right or to the left, more negative charges will gather in the same direction, while positive charges on the external surface of the conductor won't move ...
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1answer
81 views

Capacitor and energy [closed]

I have I capacitor, with $+Q$ on the bottom plate, on $-Q$ on the top plate. A student move the top plate by $dx$ along the $x$ axis. My course states that : $$d(E_{\text{kin}}+E_p+E_e)=\delta W_o + \...
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2answers
35 views

Conductor with cavity: net charge?

Suppose that we have a uncharged spherical conductor that carries a cavity with a charge $+q$ in it. The problem I am dealing with consists in answering this question: What is the field outside the ...
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2answers
106 views

Why is electricity not faster than light if all the electrons are just shifted in the wire?

https://www.youtube.com/watch?v=jbi7gJTPSXk Please check 1:33. Many people said that all the electrons are just shifted at the same time when a current flows in the wire. So electricity can move ...
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2answers
26 views

Is voltage same on the surface of conductors? (including not perfect ones)

I know that for a perfect(ideal) conductor, it should have equipotential surface. But does it hold for not perfect(not ideal) coductors? In other words, is it possible to have more than two points ...
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1answer
72 views

Electric displacement vector $\mathbf{D}$: linear dielectrics

Excuse me for this simple question, but I have occurred of a clarity for this question. The Electric displacement vector $\mathbf{D}$ is defined, as: $$\mathbf{D}=\epsilon \mathbf{E}+\mathbf{P}$$ ...
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1answer
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Voltage drop in Drude's model and the electromotive force

I'm trying to understand the meaning of the voltage drop and of the electromotive force in view of Drude's model. This model assumes a drift speed for electron equal to: $\mathbf{v_d} = \frac {-e \...
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3answers
170 views

Energy band theory: conduction of electrons and holes

My textbook, Introductory Semiconductor Device Physics, by Parker, says the following in a section on energy band theory: We are aware that conduction in most metals is by electrons but conduction ...

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