All Questions
47
questions
1
vote
1
answer
41
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Confusion about EM waves in a conductor, AC in wires, and skin effect
I am trying to get my head around these different points:
From Maxwell's equations we find that an electromagnetic wave in a conductor decays in amplitude with a characteristic length of about 1 cm in ...
- 197
0
votes
0
answers
27
views
Can you measure different currents at different contact points for a volume of material made of two different metals with different conductivities?
My question is about the variation of conductivity in a volume of material and its effect on measured current. A volume is comprised of two metals joined symmetrically in a cuboid shape as in the ...
2
votes
4
answers
1k
views
Why is current density in a conductor of uniform cross sectional area constant at all points?
According to what I was taught, if current was dispersed “uniformly,” current density would remain constant.
So, in a conductor, the 'current density should be the same at all points.' But, given that ...
- 444
0
votes
1
answer
154
views
Would a grounded copper heat sink located near a room's ceiling be an effective way to reduce a room's temperature?
I am thinking about a cheap but effective way to reduce the temperature of my bedroom in my apartment during hot summer nights. I live in an old apartment building and the air conditioner located in ...
- 478
0
votes
1
answer
73
views
Running electrolysis on inside surface of a tube
I use electrolysis for rust removal and electroplating. I notice that when one of the electrodes is a closed tube or has other topological holes with a sufficiently large height:diameter ratio, the ...
- 1,004
4
votes
6
answers
2k
views
Electric current definition
I'm trying to understand electric current. Some resources say that it is the flow of charge, and other resources say that it is the quantity of charge that passes through a cross-sectional area over a ...
1
vote
2
answers
766
views
What force moves electrons through a conductor that is rotating in a magnetic field [closed]
Is it the magnetic force ( F= qv +B ) or the electromagnetic force (F= q(E+vxB) that acts on the electrons of a conductor that is moving in a magnetic field?
Thanks.
user232620
0
votes
1
answer
71
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How is electric current possible if no electric field exists inside a conductor?
How is electric current possible if no electric field exists inside a conductor?
Since no electric field exists inside a conductor. How is electric current possible as $$v_d=\frac{(eE)t}{2m},\;\;{E=0}...
- 1
3
votes
1
answer
698
views
Does the shape of a wire affect the electric current in it in any way?
Say we have a straight wire connected across two terminals carrying electricity between them. If everything is kept the same (voltage across the two terminals, resistance of the wire, etc.) will there ...
- 195
5
votes
4
answers
987
views
If an electron is repelled by another electron how is it that we get an electric current?
As we know that an electric current is a flow of electric charge in a circuit, and in electric circuits, the charge carriers are often electrons moving through a wire.
Now, since we know that like ...
0
votes
1
answer
63
views
GENERATION OF CURRENT DUE TO ELECTRON FLOW
Why do flow of electrons generate current? whenever an electrons flows through a wire it generates electricity why does it actually happen?
- 31
3
votes
3
answers
235
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What do $\ell$ and $A$ precisely mean in the formula for electrical resistance?
The formula for resistance is
$$R=\rho\frac{\ell}{A}$$
Generally in most of the textbooks it simply written that $\ell$ is the length of the conductor and $A$ is it’s cross-sectional area. But my ...
- 155
1
vote
1
answer
94
views
Does the electron in wire too move because of voltage difference?
When we talk about electricity through a circuit because of a battery it is said that the electrons from negative terminal travel to positive terminal of the battery.
I can't help but imagine about ...
- 300
0
votes
0
answers
614
views
Current equation $I=nqA\vec{v}_d$
I was reading from several introductory E&M materials, and they all state that $$I=neA\vec{v}_d$$where $n$ is number of free charge carriers, $e$ is the elementary charge of electron, $A$ is cross-...
0
votes
1
answer
121
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 ...
- 1
0
votes
2
answers
148
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 ...
- 3
2
votes
1
answer
362
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 ...
2
votes
1
answer
2k
views
Skin Effect Explanation
I do not understand some things about the Skin Effect.
Its Wikipedia definition is:
Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor ...
- 1,319
0
votes
1
answer
3k
views
Why can't free electron flow in water to conduct electricity?
This question is related to how batteries work. In a battery, the electrons can only flow in conductors, because they can't flow in the solution.
my own thoughts on the matter:
I believe it is ...
- 103
-1
votes
1
answer
66
views
How electric current is defined in a metal wire?
How current is defined if in a metal wire both positive and negative charge exist? Isn't the total charge/time 0?
- 1,648
0
votes
1
answer
2k
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Charge accumulation in wire
I came across a question about charge accumulation. It states that if a steady current flows in a wire composed of a copper and iron wire of same area (see fig), will the charge accumulate on the ...
- 143
0
votes
2
answers
465
views
How does the current become homogeneous within a circuit?
I have two questions:
In a given circuit with resistances of different values connected in parallel, there is a different build up of electrons when the power source is turned on. Then, how is the ...
- 1,235
1
vote
2
answers
153
views
Creation of electric field inside a conductor
My book says that as soon as the two ends of a conducting wire touches the two terminals of a battery, it generates an electric field inside the conductor. Why?
- 31
0
votes
2
answers
736
views
What is drift speed in electricity and how is it related to the cross sectional area of the conductor?
In fluids dynamics, I learnt that as rate of flow is constant for an ideal fluid, Area(cross sectional area of the tube) x velocity is constant.I had a doubt whether the same relation exists between ...
- 101
1
vote
2
answers
1k
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What is the cause of opposite electric current direction of flow of current inside a battery?
My question is that why the direction of current inside a battery is different than that of outside battery?Can someone explain how current is even carried inside a battery because free electrons aren'...
- 51
15
votes
3
answers
7k
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 ...
- 314
45
votes
5
answers
61k
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 ...
- 4,711
0
votes
1
answer
197
views
What is electric current? [closed]
I have been reading a book about electricity which states that: electric current is not the movement of electrons but the "impulse generated when free electrons orderly "jump" from one atom to the ...
- 11
3
votes
2
answers
1k
views
How is the speed of electricity determined?
Before I am told this is a duplicate, I'd like to be specific here. I have searched online for an answer regarding the speed of electricity in general and haven't found what I'm looking for. Even in ...
5
votes
2
answers
695
views
Why do electrons follow the conductors shape?
I'm stuck thinking about this situation. I imagine that there are two oppositely charged objects at short distance $r$, put inside an insulator (Can I say air?). They generate a net elctric field, ...
2
votes
3
answers
1k
views
Does saline water lose conductivity over time?
When current is passed through a beaker of salt water, the ions move towards the terminals (based on their charge– e.g., sodium ions to the cathode and chlorine ions to the anode).
Following this ...
- 21
0
votes
2
answers
3k
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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 ...
- 187
0
votes
1
answer
583
views
Why are spheres supposed to become discharged?
Source of image: Fundamentals of Physics extended fifth edition by Halliday, Resnick and Walker. Concerned to First Paragraph.
Why in the rejected scheme, Spheres are supposed to go neutral (or ...
user104909
3
votes
1
answer
525
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How do electrons move at an atomic level? [duplicate]
This was meant to be a sub question in the comments of my last question but I think it is big enough to have its own post.
I know that electrons move because of the potential difference across the ...
- 705
-3
votes
1
answer
362
views
How electricity works acutally?
I've been told that electricity is due to flow of charges(-ve charge=electron) that are provided by the battery. And no. of charges that leave battery at one end are equal to no. of charges that re-...
1
vote
1
answer
163
views
How increased current carrying capacity / ampacity affects wire gauge size [closed]
In selecting a suitable wire size for manufacturing:
If I have a material that has the same resistivity and density as Copper, but has a higher current carrying capacity / ampacity for the same ...
- 11
1
vote
0
answers
2k
views
What happens to metal when exposed to an electric current for an extended period of time?
I was wondering what happens to the actual metal (copper, aluminum, silver, gold) when electricity is ran through it for a long period of time. Say years like the wire in a house. Does the ...
- 11
3
votes
3
answers
2k
views
When current passes through a wire, does it only travel through the outer surface?
In electrostatics we are taught that the field inside a conductor is always zero. So when current passes through a wire, the electricity only passes through the surface of the conductor.
In magnetism, ...
- 353
3
votes
4
answers
15k
views
How does the drift velocity of electrons in a conductor depend on the temperature?
How does the drift velocity of electrons in a conductor depend on the temperature?
I have two contradicting views for this.
First, we can say that increasing the temperature of the conductor will ...
- 1,582
-3
votes
3
answers
1k
views
How can the copper wire in an electricity generator provide an infinite number of electrons? [closed]
How can copper wire in an electricity generator produce an infinite number of electrons when the is a finite number orbiting each copper nucleus?
3
votes
1
answer
101
views
Direction of AC current in a very long wire [closed]
Suppose an external wire of length 10^8 meter (very long indeed) is connected in between the slip rings of an AC generator externally. Taking the speed of current propagation to be ~10^7 m/s, then it ...
user63923
1
vote
2
answers
1k
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. ...
- 972
0
votes
1
answer
2k
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What is wavelength of electric field generated in a wire? [closed]
I read link given below:
http://en.wikipedia.org/wiki/Speed_of_electricity
Above link says
_The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic ...
- 2,091
18
votes
5
answers
12k
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 ...
- 510
1
vote
1
answer
5k
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 ...
- 1,241
2
votes
2
answers
2k
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 ...
- 447
8
votes
9
answers
6k
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 ...
- 2,009