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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3answers
673 views

Gravitational doubt [duplicate]

If we can shield a charge from electrical forces by putting it inside a hollow conductor. Can we shield a body from gravitational influence of nearby matter by putting it inside a hollow sphere or by ...
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1answer
12k views

Why don't you get electrocuted when you jump and touch an electric fence?

I've read that you won't get electrocuted if you jump and touch an electric fence because you aren't closing the circuit with the ground. Which is also why birds don't get electrocuted when they're ...
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1answer
2k views

Filament lamp: Negative part of I/V characteristic?

I don't understand the negative part of the graph. It shows that the resistance is decreasing as the voltage goes from negative towards 0. What does a negative voltage mean and why does the graph ...
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2answers
1k views

Is there no electric field inside a conductor?

I came across this statement while studying electric currents and I am confused: "There is no electric field inside a conductor. Hence no current can flow through it". Is there a fallacy in this ...
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3answers
108 views

How fast does an electron move?

I've been reading this website: www.physics.wayne.edu/~apetrov/PHY2140/Lecture8.pdf to learn how fast an electron moves in a circuit. On page #8, #9 and #10 It says to take the Cross-sectional Area ...
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4answers
87 views

Question on direction of electric field

My physics textbook (1st year university course on Electrostatics) mentions that when looking at a positively charged metal disc from the side, the electric field is located perpendicular to the ...
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1answer
556 views

Image charge method to find electric field [closed]

The following is a question from my tutorial on boundary value problems and image charge method- A point charge +q is placed at (0, 0, d) above a grounded infinite conducting plane defined by z = 0. ...
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2answers
867 views

Migration of an ion in a non-conductive medium

Someone asked me why, when performing DNA electrophoresis we need to put the gel inside a conducting buffer. Couldn't we just run it in distilled water? My answer was that if we had distilled water ...
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3answers
289 views

Electric field inside a conductor

I would like to clear things up: How exactly the electric field inside a conductor is zero? Let a really "powerful" electric field be outside of it, how can the "few" charges in a conductor balance ...
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2answers
49 views

Why are 'low frequency' EM waves attenuated by a single layer of kitchen foil?

Can someone explain why my am radio doesn't work when covered by a layer of foil that is less than one 'skin depth' at the appropriate frequency? According to wikipedia and other websites on the ...
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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
1k views

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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2answers
543 views

Does an electron physically flow? [duplicate]

In a DC current in a conductive wire, is it more accurate to think of one electron wiggling its way through a sea of electrons... or to think of one electron bumping into another, which bumps into ...
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2answers
344 views

How can the free charges of a conductor redistribute to the surface?

I have studied that if I put a conductor (perfect or non-perfect) at rest in a place where there is an electrostatic field, the charges of the conductor will distribute so that negative charges will ...
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1answer
221 views

How to interpret Ohm's law?

I just started learning about Ohm's law and the textbook defines it as: Provided the temperature is constant, then for an Ohmic conductor the current through it is directly proportional to the ...
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5answers
13k views

What is the dielectric constant of a pure conductor?

Dielectric constant is the ratio of permittivity of a medium to the permittivity of free space. How to find dielectric constant of a conductor?
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1answer
592 views

E field of parallel plates with metal inside

I was asked to determine the electric field in the spaces between the copper bar and the plates. The voltage across the plates was 30 V, so naturally I’d use $E=\Delta V/d$ to determine the field. ...
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2answers
613 views

Why does the superposition principle work in method of images?

Okay, let there be a conducting sphere having radius $a$ initially charged with $Q$ & insulated. Now, $q$ is brought in front of the conductor at $y$ from the center. Now, Jackson in his book ...
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1answer
160 views

Does charge distribute itself uniformly on a conductor?

An excerpt from a beginning E&M book [...] In other words, the surface of a conductor is an equipotential surface under static conditions. [...] Summarizing the boundary conditions at the ...
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1answer
26 views

Electric field inside a conductor with an opening

Assume that we have a charged conductor of any shape but it has an opening so that we can get inside the conductor through that opening . Will the electric field be zero inside that conductor ? I ...
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5answers
184 views

Which type of conductors don't follow Ohm's law? [closed]

Which type of conductors don't follow Ohm's law? I know that semiconductors and superconductors don't follow them, but why? And what about ideal conductors. What are they? Do they follow ohm's law? ...
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2answers
75 views

When to use Poisson's equation in electrostatics

When does when elect to use Laplace's equation when dealing with charge distributions. For example, if I had a metallic sphere of radius $R$ and charge $Q$, then $$\mathbf E = \begin{cases} 0, & ...
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1answer
51 views

On the electric field created by a conductor

The electric field created by a conductor at a point $M$ extremely close to it is $\vec{E}=\vec{E_1}+\vec{E_2}$ where $\vec{E_1}$ is the electric field created by such a tiny bit of the conductor that ...
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3answers
231 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 ...
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1answer
66 views

Resistance Being Proportional to Length And Its Relation to Magnitude of Current

"Resistance of an electrical conductor is proportional to it length" The intuitive explanation I found in many articles was that the greater the length of the conductor, such as a wire, the greater ...
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2answers
830 views

Charged body in hollow conductor : what is the role of insulators and how does the charge distribution change if insulators vs conductors are used?

Question as written in textbook: "Figure 1 illustrates a nested arrangement of four cylindrical conductors (seen side-on in cross-section) in which the cylinders are separated by electrical insulators....
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1answer
127 views

How does the energy of a charge above a metal plate compare to two point charges?

Suppose you have the classic method of images problem. You have a point charge $q$ sitting a distance $d$ above grounded metal plate. You can then find the field as though there were 2 point charges ...
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3answers
142 views

Is there a way to measure the thickness of a metallic plate of order of micrometers?

I have a $5 cm×5 cm×? \mu m$ copper plate. Where '$?$', the thickness of the plate, is really small (about 30um). Is there anyway using physics to calculate the thickness? Update: Sorry I forgot ...
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2answers
884 views

Some questions related to circuits and flow of electrons

I have some doubts related to electric fields and flow of current. So, let us assume an electric circuit, which contains a battery and a wire connecting positive and negative terminal of the battery. ...
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1answer
132 views

Uniformly charged disk

A uniformly charged disk is an isolant or a conductor? Or could it be both of them? I only know its radius and its surface charge density, which is uniform throughout the disk.
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2answers
1k views

When doping a material, why is As called impurity?

Doping is the act of adding impurities to Group-IV elements to e.g. improve their conductivity. Though it is improving the conductivity, why is it called impurities?
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2answers
7k views

Why is the electric field zero inside a hollow conducting sphere?

If you have a conducting hollow sphere with a uniform charge on its surface, then will the electric field at every point inside the shell be 0. The reason the electric field is 0 at the center is ...
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2answers
49 views

A small size conductor causes a greater current in a circuit?

I have a question - let’s say I have a very small 2 wire cable connected to a load that draws a large amount of current, I’ve been told ( I have yet to do my own testing) that the smaller cable will ...
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1answer
64 views

What exactly does Ohm's law say?

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, R ...
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2answers
84 views

Hydrogen: Whether it's a metal or non-metal

I know hydrogen is a non metal, but when I just study about some introductory elementary band theory I find the band structure of hydrogen has a half filled valence band just like alkali metals, and ...
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1answer
57 views

Relativistic effect in a current carrying wire

In many places I read that in the rest frame of a current carrying wire (electrons in motion), the spacing between the positive ions is length contracted and equal to the length contracted spacing ...
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2answers
144 views

The image charge inside the conducting sphere without producing any electric field [closed]

In the method of images for a grounded conducting sphere, we calculate the position of image charge at $$\frac{R^2}{r}$$, due to which there should be an electric field inside the conducting sphere ...
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3answers
1k views

Non-ohmic conductors

Non ohmic conductors are said to be the conductors that do not obey Ohm's Law. The V-I graph for them is not a straight line unlike ideal ohmic conductors. According to me Ohm's Law states: The ...
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2answers
65 views

Is it the current which create magnetic field, or vice versa, or both?

Talking about stationary magnetic field, it is said that if a conductor rotates inside the field, a current is induced. Also, I read that current (moving charges) generate magnetic field, too. How are ...
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2answers
176 views

How is voltage proportional to current?

The question came up in another forum - "What causes current to flow". Many knowledgeable people explained that what causes the flow of charge are electric field forces or Coulomb forces. If there is ...
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1answer
151 views

Charge Distribution on Conductor - Uniform or Not?

Consider a hollow conducting spherical shell S1 inside an irregularly shaped conducting wall S2 (in the figure). The sphere S1 is somehow given a charge +Q. Will the charge distribution on S1 be ...
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2answers
350 views

Why does charge distribute itself uniformly only on the surface of spherical conductors?

I understand why charge does not distribute itself uniformly on the surface of a conductor of any other shape. I do not understand why charge distributes itself uniformly only on the surface of a ...
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2answers
62 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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2answers
271 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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1answer
169 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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1answer
401 views

Magnetic field in perfect conductor : how to decide the “initial value” as $B=cste$

In a superconductor, we have no magnetic field because of Meissner effect. In a perfect conductor, as $\vec{E}=\vec{0}$, we have $\frac{\partial \vec{B}}{\partial t}=\vec{0}$. Thus the magnetic ...
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2answers
137 views

Why are hollow conductors used for signals of a certain frequency?

So this question is really about skin depth. I have been introduced to the skin depth by a simple model (simple equation for electrons in a metal with a damping term) of polarisability for a metal. In ...
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2answers
1k views

Is it safe for a man standing inside a Faraday cage to touch it from inside

Will a man get electrocuted if he touches a Faraday cage from inside when a high potential difference is developed between a Faraday cage and some other source? If yes then how a person wearing ...
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1answer
164 views

Electric field inside a conductive spherical shell [closed]

We have a conductive spherical shell and a point charge $q$ near it. And Is the field inside the spherical shell (where is in fact not inside of the conductor) zero?
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5answers
243 views

Electric field in conductor at equilibrium: explanations seem to be lacking

I'm trying to understand why the field is zero. This is not a duplicate of previous similar questions because I'm questioning the standard explanations. I've seen two explanations: Gauss's law. A ...