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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58 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
724 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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32 views

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
148 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
62 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
36 views

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
10 views

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
28 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
22 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
88 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
38 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
47 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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23 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
32 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
69 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
154 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
91 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
59 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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0answers
35 views

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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2answers
29 views

Energy Bands Question [closed]

When an electron passes into the valence band, is it no longer useful for conduction?
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0answers
25 views

Conductivity of silver [duplicate]

What makes silver the best conductor of electricity? I want to know in terms of electrons. Although, Cu and Ag and many other metals have only one electron in their valence shell. Then what makes Ag ...
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0answers
21 views

Does net charge on a conductor sit only on outer surfaces?

Suppose we had a hollow conducting sphere with a net charge q on it. There is no charge in the cavity; the conductor itself has a charge q. The idea is that this net charge would reside on the '...
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1answer
57 views

What is the correct interpretation of Electric flux? (beyond a mathematical formula)

From when I first learned flux and till now, I was thinking of flux as a measure of 'flow'. Now, this interpretation breaks down if you consider conductors as I will show below. Here, there is abrupt ...
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1answer
25 views

Charges in a conductor

When a conductor is placed in some external electric field, why can't the free electrons just escape out of it? Is the positive charge distribution on the opposite side(surface) always strong enough ...
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1answer
48 views

Why equal sign wasn't used for boundaries for radius ($r < b$) between internal and external conductor?

Why boundaries for radius between internal and external conductor are set to $a \leq r < b$ instead of $a \leq r \leq b$? Example: An air coaxial line made of copper ($μ \sim μ_0$) is given. A ...
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14answers
798 views

Why is the field inside a conducting shell zero when only external charges are present?

In many introductory books on electrostatics, you can find the statement that the field inside a conducting shell is zero if there are no charges within the shell. For example, if we place an ...
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1answer
36 views

Why are non-metallic elements with partially filled valence bands not conductors?

Throughout this whole question, I will be referring solely to single element solids. According to band theory, ns and np bands are close enough in energy to overlap and create one band with 8N states ...
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1answer
98 views

How much charge will flow to the earth?

Consider a thin spherical conducting shell of radius $R$, which carries a total charge $Q$ on its surface. Two point charges $Q$ and $2Q$ are at A and B respectively as shown in the figure ($C$ is the ...
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2answers
49 views

Flux inside the cavity of a conductor

Assume a perfectly spherical conductor with a spherical cavity inside it. Say we place a charge $+Q$, at the center of the cavity. It induces a charge $-Q$ on the inner wall of the cavity, and a $+Q$ ...
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1answer
16 views

Insulator or conductor with different boundary conditions

I'm studying the 1-D SSH model. It's a toy model for a topological insulator. Here's the reference I'm using. If the hopping amplitudes $v$ and $w$ are equal, then with periodic boundary conditions we ...
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1answer
33 views

Grounded conducting sphere with cavity (method of images)

If I have a grounded conducting sphere with a cavity [radius $R$] that has a positive charge inside, using the image method to calculate the electric field I have to use an imaginary charge. My ...
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0answers
25 views

Self-energy of a conducting shell when we put some charge inside it

We already know that if we have a conducting sphere with total charge $q$, then the self-energy of the sphere is $\frac{q^2}{8\pi\epsilon R}$, where $R$ is the radius of the sphere. But my question is,...
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1answer
22 views

Current passed through a charged conductor

If I take a charged conductor and pass a current through it and stop. Will the charge remain on that conductor or would it be flown away by the current?
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1answer
11 views

Charging Insulators

Can insulators like plastics be charged with the help of conduction? What happens when such materials are brought in contact with charged bodies that might be conductor or insulator?
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2answers
42 views

Two spherical conductors $B$ and $C$ having equal radii and carrying equal charges on them repel each other with a force $F$

Two spherical conductors $B$ and $C$ having equal radii and carrying equal charges on them repel each other with a force $F$ when kept apart at some distance. A third spherical conductor having same ...
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2answers
56 views

How do we know that any two points of an ideal wire must be equipotential? [duplicate]

How do we know that any two points of an ideal wire must be equipotential whether or not there is a current flowing through it? I fully understand that how the electric field in a conductor in ...
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0answers
24 views

How to obtain the optical constants (dielectric function or complex conductivity) of a material from its band structure?

I know that the complex conductivity ($\sigma = \sigma_1+i\sigma_2$) is related to the dielectric function ($\epsilon = \epsilon_1+i\epsilon_2$) by: $$ \epsilon_1 = 1 - \frac{4\pi\sigma_2}{\omega} \\\...
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2answers
46 views

The Electric Pressure Bomb: Can a conductor rupture due to its own electric pressure?

So I conducted a though experiment where I take a hollow spherical conductor and beef it up with a lot of electric charge. Here, I have ignored the ionization of air due to that huge amount of charge. ...
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3answers
38 views

Argument for electric field inside spherical shell

If I have a conducting spherical shell of outer radius $R$ and inner radius $r$, the electric field inside is $0$. The argument commonly given is: Pick a point $P$ inside the shell (i.e. radius < $...
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1answer
42 views

Different drift velocities in the same conductor

We know unlike charges attract and like charges repel. The magnitude of this force of attraction or repulsion decreases as the distance between the charges increase. As a result the force exerted due ...
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1answer
32 views

Charge transfer in two different metals by touching them

When we touch two metallic conductors one is neutral and other has excess of charges, Case 1- Both metals are of copper, then we can calculate actual charges on them at steady state by capacitance ...
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3answers
58 views

How do electrons in metals manage to have zero acceleration in constant $E$ field (as in a DC circuit)?

From Newton's second law, a charged particle driven by a constant electric field should move with a constant acceleration. But electrons in a circuit acquire a steady average velocity which gives rise ...
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3answers
110 views

What do $\ell$ and $A$ precisely mean in the formula for electrical resistance?

The formula for resistance is $$R=\rho\frac{\ell}{A}$$ Generally in most of the textbooks it simply written that $\ell$ is the length of the conductor and $A$ is it’s cross-sectional area. But my ...
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1answer
65 views

Can Current move without potential difference? [duplicate]

Consider the circuit given below, At the lower left corner of the circuit assume potential to be $0\ V$ , Now at the upper left corner current should be $9\ V$ and similarly at the upper right corner, ...
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1answer
35 views

Does an infinite conducting plate entirely shield off the magnetic field?

Let's say we have an infinite current-carrying wire parallel to an infinite conducting plate. Is the magnetic field behind the plate zero? I would say yes, because the field in the plate is zero. Also ...
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3answers
87 views

In metals the conductivity decreases with increasing temperature?

I am currently studying Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th edition, by Max Born and Emil Wolf. Chapter 1.1.2 Material equations ...
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2answers
103 views

Does drift velocity depend upon cross sectional area of the conductor? If yes then how? [duplicate]

I am confused whether drift velocity depends upon area or not . I checked answers for this question but all of them were cancelling each other out . from the equation $$I = neAv$$ It is clear that ...
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0answers
22 views

Does Drude theory work better in solutions than in metals?

Things tend to be more classical the bigger they are, so I guess the area where the Drude model (the one that explains resistivity with classical scattering) would work best is when the charge ...

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