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.

Filter by
Sorted by
Tagged with
125
votes
4answers
31k 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 ...
56
votes
6answers
23k views

If water is not a good conductor, why are we advised to avoid water near electricity (no wet hands near circuits etc.)?

How can water be a medium to conduct current while its ionisation is so negligible that, in principle, no current should flow?
51
votes
9answers
46k views

Does electricity flow on the surface of a wire or in the interior?

I was having a conversation with my father and father-in-law, both of whom are in electric related work, and we came to a point where none of us knew how to proceed. I was under the impression that ...
36
votes
5answers
23k views

Speed of light vs speed of electricity

If I arranged an experiment where light raced electricity what would be the results? Let's say a red laser is fired at the same time a switch is closed that applies 110 volts to a 12 gauge loop of ...
27
votes
3answers
11k views

How does electricity propagate in a conductor?

On a systems level, I understand that as electrons are pushed into a wire, there is a net field and a net electron velocity. And I've read that the net electron drift is slow. But electricity ...
24
votes
6answers
4k views

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, ...
21
votes
5answers
4k views

Why don't free electrons escape from a conductor?

The thermal velocity of the free electron in a metallic conductor varies from $10^5\ \mathrm{m/s}$ to $10^6\ \mathrm{m/s}$. In spite of high velocity, free electrons fail to escape from the metallic ...
16
votes
5answers
9k views

How does a wire carry alternating current?

Consider a simple network of a bulb whose two terminals are connected to two wires with open ends A and B respectively A o--------💡--------o B Now if a DC ...
16
votes
6answers
1k views

What keeps electrons on a negatively-charged conductor from leaving?

Imagine a negatively charged conductor in a vacuum. The excess electrons will be spread out over the surface such that the net electric field inside the conductor is zero. What keeps these extra ...
15
votes
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 ...
14
votes
4answers
2k views

Are insulators and conductors arbitrary categories?

I have seen charts showing the transition from insulator to semi-conductor is at $10^{-8}~\frac{\text{S}}{\text{cm}}$ and between semi-conductor and conductor is $10^{3}~\frac{\text{S}}{\text{cm}}$. ...
14
votes
6answers
2k views

Can a conductor run out of electrons to cancel external electric fields?

We have studied so far that electric field inside a conductor if no charge is placed inside is zero. But we know that every conductor has only a limited number of electrons. What happens when ALL the ...
13
votes
3answers
4k views

What is it about the “conduction band” of a material that is distinct from the valence band?

I'm taking a course in nanotech and we're discussing nanoelectronics. This has led to a discussion of conductors, semiconductors, and insulators. I have a number of lovely diagrams explaining the fact ...
12
votes
3answers
3k views

If we remove all electrons from a conductor, how can the positive charge rearrange itself?

Explanations of conductors in electrostatics that I have encountered seem to describe positive charge spreading out, because you could say that lack of electrons can be thought of as abundance of ...
11
votes
2answers
8k views

Where do all these electrons come from? [duplicate]

I'm a high school student and I'm fairly familiar with basic electronics, but I've always wondered one thing. So how generators make electricity from motion is the move a magnet around or through a ...
11
votes
5answers
11k views

Why is there an electric field in a wire even though it is a conductor?

If you take a perfect conductor, there cannot be a field across it since if there were, the particles would arrange themselves in a way to cancel out the field right? Yet, why does the same not hold ...
11
votes
1answer
196 views

Why there is no hole in Sommerfeld's model of free electrons?

My question is very naive. I don't understand why there are no holes in Sommerfeld's model of free electrons? Whenever an electron is excited above the Fermi level $E_F=\mu(0)$, there should be a hole....
10
votes
2answers
2k views

Do electrons move around a circuit?

We could imagine a simple electronic circuit composed by a power source and a resistor. It is usual find descriptions as "The moving charged particles in an electric current are called charge ...
10
votes
6answers
49k views

Why is the electric field perpendicular to every point on the surface of a conductor?

I am reading Berkeley Physics Course, Volume 2 (Electricity and Magnetism by Edward M. Purcell). I am in chapter $3$, page $92$, and the book discusses conductors. The following is from the book: ...
10
votes
9answers
66k views

Why is the charge transferred by electrons and not by protons?

Charges are transferred by electrons which we all know. But why can't it be transferred by protons? Well, I searched on Google where I found similar questions already being asked on many sites. ...
9
votes
4answers
10k views

Why does a short circuit generate fire?

When a short circuit occurs it's obvious that there is fire. How come electric energy turns out to be heat energy? What causes the conductors to get hot when short circuit is present.
9
votes
4answers
14k views

How does positive charge spread out in conductors?

I know that when there are excess positive charges in a conductor, for example, a metal sphere, the positive charges will spread out over its surface. However, I am confused about how this excess ...
9
votes
1answer
5k views

Why does electrical current start to flow?

What happens microscopically when an electrical current starts to flow? I'd like to understand microscopically what happens in detail when electrons start moving (quasi-classically). Electrons can ...
9
votes
2answers
2k views

Why do liquid metals conduct electric current?

This is a question I wanted to ask for some time now. You learn in solid state theory that the free electron model is the reason for metals conducting electric current. The electron orbitals ...
8
votes
3answers
4k views

Why don't get I shocked in an electric shower if the resistance makes contact with water?

I've found this image that perfectly illustrates my shower. I've read somewhere that the resistance is insulated so even if it touches the water, it doesn't conduct. However, as you can see, the ...
7
votes
3answers
630 views

Voltage as electromotive “force”

Considering the "water analogy" for electricity, it seems voltage is sort of like gravity: (image source: http://learn.olympiacircuits.com/electricity-flows-like-water.html) Now when water actually ...
7
votes
5answers
2k views

How to show mathematically that the electric field inside a conductor is zero?

The electric field is characterized by the equations $$\nabla\cdot \mathbf{E} = \dfrac{\rho}{\epsilon_0}$$ $$\nabla \times \mathbf{E} = 0$$ Or equivalently, $\nabla^2 V = -\rho/\epsilon_0$ and then ...
7
votes
5answers
9k views

Why is the electric field inside a conductor zero in equilibrium?

My textbook says the field inside a conductor must be zero in order for the system to be equilibrium and therefore there must be no excess charge inside. Their proof: 1) Place a gaussian surface ...
7
votes
3answers
16k views

If the current is increased, is there more charge flowing or is it moving quicker?

Problem Current is the amount of charge that is flowing through a component per unit of time. For a given voltage, Ohm's law tells us that if we increase the resistance, then the current must ...
7
votes
2answers
11k views

How do bits get transferred over a copper wire?

I've been a programmer for a while, and I've done a little bit of network programming, but I'm wondering, how do bits get transferred over a copper wire? What counts for a 1 & what counts for a 0?...
6
votes
3answers
1k views

Why does my measured I-V curve for a film of aluminum suggest high resistance?

I plotted the I-V curve between two points (few microns apart) on a thin aluminum film. I expected this metal to be a conductor and have a much lower resistance, but the slope suggests that it is ...
6
votes
3answers
13k views

When two spheres of equal charge make contact, why does the larger sphere gain more charge?

Suppose that two spheres, $S_1$ and $S_2,$ with radii $R_1$ and $R_2$ resp. have the same uniform charge $Q$ and $R_1 > R_2.$ After they are forced to come in contact, why does $S_1$ gain more ...
6
votes
7answers
4k views

Why does electricity need wires to flow?

If you drop a really heavy ball the ball's gravitational potential energy will turn into kinetic energy. If you place the same ball in the pool, the ball will still fall. A lot of kinetic energy will ...
6
votes
2answers
432 views

From where do electrons gain kinetic energy through a circuit?

Supposing an ideal wire, How do electrons accelerate and gain kinetic energy? What I understand: When a circuit is opened ,electrons are crowded at the negative term of the battery and have high ...
6
votes
4answers
642 views

Can a positively charged conductor have negative surface charge density somewhere?

This is a simple question that occurred to me while thinking about electrostatics. Let's consider a positively charged isolated conductor in equilibrium. In general, the surface charge density varies ...
6
votes
1answer
1k views

Grounding system of conducting plates

So, I always make mistakes on problems such as this (the grounding part), so I'm hoping someone could really explain to me how the process works. There are $n$ large parallel plate conductors ...
6
votes
1answer
17k views

Can a salt water solution conduct electricity forever? [closed]

We know that very pure water does not conduct electricity, but salt water is a decent conductor. This is commonly explained by saying that "the ions carry the current through the solution", an ...
5
votes
4answers
863 views

Work done by magnetic field on current carrying conductor

Suppose a wire of length L carrying a current I is kept in a uniform magnetic field B perpendicular to the current. The force on the wire will be IBL and work done by magnetic force when wire moves a ...
5
votes
4answers
4k views

Path of EM wave propagation in a circuit wire

The image is my visualization of drift velocity and electromagnetic (EM) propagation of charge wave in a closed circuit. The slow drift velocity of the electrons follows the path of the circuit (a ...
5
votes
2answers
2k views

Does a conductor of total charge zero placed in a uniform external electric field experience net force?

The question I have in mind is: If we place a conductor (arbitrary shape) of total charge zero in a uniform external electric field $\textbf{E}_0$, does it experience any net force? Why (not)? Now I ...
5
votes
2answers
17k views

Why is the electric field inside a charged conductor zero in the electrostatic case?

I am trying to understand the idea (or the fact) that most books introduce which is about the electric field inside a charged solid conductor. Books tell that the field has to be zero everywhere ...
5
votes
2answers
190 views

How far do electrons actually move along a conductor under an alternating current?

This is more or less a curiosity question. But I have had really good luck with stack exchange so far. If I can expand on my question a little bit - it may not be super important, but I know under say ...
5
votes
5answers
13k views

Conductors and their charge?

Why does excess positive charge stay on the surface of a conductor? This is what I understood from: How does positive charge spread out in conductors? and other resources on the web: If there is a ...
5
votes
1answer
476 views

Why do electrically conductive materials tend to be thermally conductive?

It's hard finding substances that are good insulators of one and conductive of the other. Why the correlation? And why do some materials not have this correlation?
5
votes
2answers
1k views

Why is the electric field inside a charged conductor zero?

When a neutral conductor is positively charged , the excess charges move to the boundary. Initially, inside the conductor there exist a field due to these excess charges which as per my reading ...
5
votes
1answer
6k views

Why isn't ice a good electrical conductor?

Water can conduct electricity, and some solids can conduct. Why can't ice? Are ice molecules too packed together to let valence shell electrons bounce across each other to create electrical charge? ...
5
votes
2answers
27k views

How to know what materials are good conductors of electricity?

I'm not asking a question like "Is the wood conductive?". No. I'm asking what properties do they have to have to be good conductors. Theoretically I mean.
5
votes
4answers
409 views

What do we mean when we say an electron collides with a molecule or atom?

When current flows through a conductor, it is said that the flowing electrons collide with the molecules or atoms of that conductor which causes resistance. The collision of electrons with molecules ...
5
votes
2answers
2k views

How can the work done in bringing a charged particle from infinity to a grounded conductor be zero?

Suppose we have a grounded conducting sphere (potential of sphere = 0) and we bring a charged particle to its surface. Since work done by us would be equal to the change in potential energy of the ...
5
votes
2answers
1k views

Charge distribution on a conducting solid disc [closed]

Imagine that you have a disc of radius $R$ with charge $Q$ on it. It is a conducting disc. What would be the charge distribution? Is there a uniform distribution over whole area? $\sigma=\textrm{...