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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25 views

Conduction current in a lossy dielectric due to a nearby static point charge

I'm a bit confused about how a steady current can apparently exist in an isolated object. Note that I'm only considering the static case here. Consider an object in free space with permittivity $\...
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1answer
33 views

Oblate spheroid conductor [closed]

Oblate spheroid coordinates $(\xi, \eta, \theta)$ are related to cylindrical coordinates $(r, \theta, z)$ as follows: $r=\sqrt{\frac{(\xi+a^2)(\eta+a^2)}{a^2-b^2}}, \theta=\theta, z=\sqrt{\frac{(\xi+b^...
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Stationary conductor in a time varying magnetic field, emf equation

A question has been asked before, but hasn't got a detailed answer. For a conduction loop in a time varying magnetic field, we get the emf as the rate of change of flux in inside the loop. But, in the ...
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2answers
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Why does the conduction band conduct in the SSH model?

I am reading "A short course on topological insulators" https://arxiv.org/abs/1509.02295. There is a basic point that I don't understand about conduction and the band structure. ...
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1answer
64 views

Do induced currents in a conductive surface result in significant electromagnetic fields outside the surface?

Consider the situation of a plane electromagnetic wave in vacuum incident normally on an interface with a good conductor. Within the conductor there is a small transmitted electric field (proportional ...
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3answers
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Electric field inside conductor is zero though we are getting $E$ inside Solid Sphere

I know that the electric field inside a perfect conductor is zero as all the charges resides on its surface to minimize its energy but if it's true then why we are still getting the electric field ...
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Potential outside long rectangular conductor

So I have a long conductor with a rectangular cross section (sides a and 2a). All sides have zero potential and one of the small ones has a constant potential $V_{0}$. Finding the potential inside is ...
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1answer
22 views

Why does potential of a conductor decreases if a negatively charged conductor is brought near a positively charged conductor?

Also, how should I imagine potential in my mind? How should I picture it?
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Work to induce charge on grounded conductors

I'm currently studying Method of Images in Griffiths book and in section 3.2 he introduces the method of images for a point charge at a distance $d$ from a grounded conducting plane at potential $V = ...
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1answer
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Why Diode breakdown allows heavy current with a constant potential, but conductors fail to do so?

A conductor, metallic is considered to be containing a sea of mobile electrons. When a diode breakdown happen, we actually have a lot of electrons inside the depletion region that are inside their ...
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1answer
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Skin effect in a 2D conductor

We know that the skin effect is the tendency of current to flow mainly near the surface of a conductor that happens when it is driven by a time-varying current. This situation is usually explained in ...
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1answer
25 views

Electric Field Outside a Conductor and Dielectric

I know that an electric field just outside of a conductor is E = local surface charge density / epsilon_0. If the surroundings of the conductor is a dielectric with permitivitty epsilon_1, does the ...
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1answer
61 views

Relation between radius of curvature and charge density

As we know in electrostatics, a metallic surface is equipotential and any charge residing on it miraculously enough distributes itself such that the conductor becomes equipotential. The surface charge ...
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Set the boundary conditions for the electric field at the separation surface between a dielectric and an ideal conductor?

In an ideal conductor (sigma goes toward the infinite), there can be no electric field within it. But neither can there be a tangential component on its surface. Based on this, set the boundary ...
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1answer
32 views

Does the electric displacement field account for free charges?

I'm trying to understand the electric displacement field $\mathbf{D}$ for a lossy material with conductivity $\sigma$ and permittivity $\epsilon$. Most textbooks I've looked at only consider perfect ...
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Weak localization, strong localization, and localization without a metal-insulator transition

As I begin to read literature on Anderson localization by disorder, authors are distinguishing between cases that are unfamiliar to me, namely weak localization, strong localization, and localization ...
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1answer
33 views

GENERATION OF CURRENT DUE TO ELECTRON FLOW

Why do flow of electrons generate current? whenever an electrons flows through a wire it generates electricity why does it actually happen?
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2answers
50 views

Electric field inside a non-conducting shell with a charge inside the cavity

I have read about conducting charged shells and spheres and know somewhat about the electric fields associated with them. But I have never found anything on non-conducting shells. I have searched ...
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1answer
53 views

Feynman's proof that field is zero in cavity of conductor

In the context of this page, I have more or less understood the proof and I have written a summary below: Consider any Gaussian surface inside a large surface which contains the cavity. Flux through ...
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1answer
44 views

Charge on infinite planes at zero potential

I am looking for some help with a problem of Electrostatics. Let us consider three parallel conducting slabs $P_1, P_2, P_3$ of a certain surface $S$, small thickness and mutual distance $d$. We know ...
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47 views

Charge moving in a wire; or not

A current flowing through a wire creates a magnetic field. A current flowing through a wire represents electrons moving very slowly in the wire. A wire contains electrons. If I have an isolated ...
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1answer
35 views

Potential below a grounded conducting plane

If I have a charge $q$ above a grounded conducting plane, I know I can calculate the potential of the charge using image method. Since the plane is grounded, would the potential below the plane be $V=...
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0answers
28 views

Charge distribution conductor in electric field

Surface charge density of a conductor at a particular region on its surface is inversely proportional to the radius of curvature at that region. But this is valid only when there is no external ...
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1answer
30 views

Charge density of Conductor

Surface charge density of a conductor at a particular region on its surface is inversely proportional to the radius of curvature at that region. But this is valid only when there is no electric field. ...
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4answers
116 views

Why is there a finite current density but zero free charge density inside a resistor in DC?

If we take a (lets imagine cylindrical) resistor in DC (steady state), we have that the electric field follows Ohm’s law: $\mathbf J_f=\sigma \mathbf E$. where $\mathbf J_f$ is the free electron ...
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1answer
18 views

Why can't excess charge built up in a conductor escape the object?

When you add electrons to an insulator the electrons stay where you place them and are unable to move whereas in a conductor they repel each other and move to the edges. Why don't the charges just ...
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1answer
37 views

Electric fields and a conductor

I'll quote the lines from my textbook- "Consider a charged conductor with a small area element ds. Assume we have two points A and B just at the surface and well inside the conductor, ...
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1answer
31 views

When you introduce excess charge into an insulator the charge stays still. Why is this?

When you add charge to an insulator the electrons stay in the same place whereas in a conductor they spread apart. Why is this? What force is making the excess charge stay in one place in an insulator?...
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28 views

From where does a grounded conductor gain charge?

Say a conductor is grounded and its potential is $0$. Now if we bring other charges near this conductor, they may cause the conductor to have a certain net non zero charge with the potential on the ...
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2answers
62 views

How does having free electrons make something a conductor?

My question is how does having free electrons make something a conductor? I know that the flow or movement of electrons create a current but can't you just add free electrons (such as a battery) to an ...
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0answers
31 views

What makes a conductor able to pass electricity?

My question is what makes a conductor able to pass electricity? I know that conductors have free electrons where as insulators don't have as many but can't you just add free electrons to the insulator ...
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4answers
758 views

In a circuit, does a battery create electrons which it 'injects' into the copper wire? [duplicate]

Are electrons created from a battery and then 'injected' into the copper wire? If no, does that mean the battery loses power because the copper wire has run out of free electrons?
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2answers
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Why can't information be conducted out of a black hole? [closed]

Why can't information be conducted out of a black hole? Does gravity affect conduction? What is the temperature profile in equilibrium of a metal pole half in, half out of a very large BH such that ...
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2answers
189 views

Does electric field reaches maximum exactly at the surface ($r = a$) or slightly above ($r = a+0$) in example with charged conducting sphere?

A sphere of radius $a$ is in the vacuum and it's evenly charged with charge quantity $Q$. Does an electric field has maximum exactly at the surface ($r = a$) or slightly above the surface ($r = a+0$) ...
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1answer
69 views

What would happen to a piece of copper if it were to suddenly lose all its valence electrons?

I am wondering what would be the result if a piece of copper were to suddenly lose all its valence electrons, or in other words, if a piece of copper was to suddenly become a collection of copper ...
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1answer
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Charge on the plate of the capacitor

I was reading parallel plate capacitors in my book today and there I saw that the battery provides +Q charge to positive plate and -Q charge to negative plate? But we know that only electrons can flow ...
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0answers
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Potential difference in a conducting ring placed in a changing magnetic field

Say we have a conducting ring of constant radius r, placed in a perpendicular magnetic field, which changes at a constant rate dB/dt. Now, there will be an emf induced in the ring given by ℰ=-d(BA)/dt=...
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1answer
31 views

Properties of conductors

If there is a cavity inside a conductor and a charge is placed within it then what exactly happens? I've read in one book that the charge in the cavity induces a charge (the induced charge is opposite ...
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1answer
23 views

Property of conductor

So I read from a book that if a charge is injected anywhere in the conductor it must come over to the surface. But when I read another paragraph from the same book, it was given that when a charge +Q ...
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1answer
120 views

Electric and magnetic fields boundary conditions

For a perfectly conducting and perfectly dielectric interface, I understood that tangential component of electric field is zero and continuous. But I have read that the normal component of magnetic ...
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1answer
55 views

Understanding conductivity at nanoscale and validity of Ohm's law

Nanoparticles such as gold and silver are becoming more and more used to print circuit or enhance electrical properties of another material. But I have not been able to find sources that clarify how ...
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1answer
51 views

Why the electrons in a insulator fill up the valance band exactly?

The classic picture of the band structure for an insulator is a filled valance band below $E_F$ and empty conduction band above $E_F$. This picture seems to me that the electron density is fixed. For ...
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29 views

Potential on a charged plate

We all know that at any point potential can be defined. When we say a capacitor is charged to a certain potential we mean that the plates acquired some charge, having a potential difference between ...
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2answers
38 views

Electric field inside a conductor under influence of non uniform electric field [duplicate]

Suppose a conductor is placed in a non uniform external electric field. Why does the field inside the conductor remain zero?
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5answers
108 views

Maxwell-Boltzmann distribution in conductors?

In the kinetic theory of gases, the Maxwell-Boltzmann distribution is commonly used to describe the velocity distribution of gas molecules. My question is to what extent (if at all) can such a ...
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6answers
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Why do metals have free electrons?

Throughout my highschool classes, I have been made to learn that metals have free electrons that's why they are able to conduct electricity.. But I never understood why. Is that related to metallic ...
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3answers
158 views

Why is the heat flow in metals slower than the current flow?

When we apply a voltage across a metallic conductor, the current starts to flow almost instantaneously. But when a temperature difference is established across the same conductor, the flow of heat is ...
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2answers
107 views

What is the capacitance of a spoon?

Has anyone measured it? I can't seem to find anything online for "spoon capacitance"; what's the expected (self-)capacitance on the typical household utility metal spoon? The spoon heads ...
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2answers
95 views

Can I ground myself to a spoon?

Laptop upgrade tutorials advise grounding oneself to metal objects ultimately connecting to literal ground (floor, Earth), such as the laptop's metal case, or a metal door, heater, etc. Is this really ...
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Work-Energy Theorem in Resistance circuit with variable Voltage

Consider a simple resistance circuit with constant Voltage. At any stage current is constant and the drift velocity of electrons is same.The change in Kinetic Energy is zero and the work done by ...

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