All Questions
Tagged with electricity electric-current
97
questions with no upvoted or accepted answers
4
votes
0
answers
132
views
Why do lightnings generated by a tesla coil also move upwards?
I was recently watching some videos of Tesla coils, and the behavior of the rays caught my attention. In the picture below, you can see how the coil is emitting lightnings, some of them towards the ...
4
votes
3
answers
369
views
Maximum practically possible current value for high frequency alternating current in metal conductor
Is it practically possible to reach 1 A current AC in the metal conductor with frequency 2 GHz?
Or in other words, if I have plain metal wire, or maybe a thin tube/foil to reduce skin effect, what is ...
- 788
4
votes
1
answer
223
views
At what distance is lightning dangerous for someone lying down?
My 8 yo child told me that they learned at school that they should lay down flat on the ground in case of lightning. I told him that the more correct position is crouching down with feet together, but ...
- 516
3
votes
3
answers
856
views
What is the significance of direction of current density?
I studied the equation for current density
$$I=\vec{J}\cdot\vec{A}$$
but nowhere is the significance of the direction of current density mentioned.
Also, I want to know why we use dot product instead ...
- 43
3
votes
1
answer
722
views
Why is lightning going from the Earth to the clouds while the electrons are going from the clouds to the Earth?
The lightning is often a discharge in advance. The (negative) charge slide occasionally a little further on in the conductive channel, wherein said channel is highlighted each time something. The ...
- 3,348
3
votes
1
answer
1k
views
Distribution of current of a rotating cone
If I have a hollow cone (surface with no bottom cover ) as the one in the picture. The cone has surface charged density $\sigma$. It rotates around the symmetry axis with an angular velocity $\omega$. ...
- 738
2
votes
0
answers
40
views
Does the power state of an electrical device affect its likelihood of being struck by lightning?
Holidaying in the tropics, I have come across the following behaviors which are all intended to reduce the likelihood of attracting a lightning strike when in a storm.
Turning off the CD player/radio ...
- 21
2
votes
1
answer
105
views
Current through a junction of two metals
When a current flows through a junction or a contact between two metals of different conductivities a charge is accumulated in the vicinity of contact. The charge accumulated, I've read, is directly ...
- 1,638
2
votes
1
answer
134
views
Does electrical sawtooth wave actually produce sinusoidal oscillations at harmonic frequencies?
According to Fourier's theorem, we know that a sawtooth wave can be represented as a sum of sine waves. These sine waves we know as harmonics (in the context of sound). My understanding is that it is ...
- 21
2
votes
1
answer
128
views
Electron Flow Notion
I would like to ask something that bothers me. A lot of us know of the electron flow notion, which it is the technical representation of how the electron charge really flows, starting from the ...
- 21
2
votes
0
answers
846
views
Drift velocity of electrons in a superconducting loop
Do electrons travel at the Fermi velocity in a superconducting loop?
For metals the Fermi velocity seems to be around $10^6$ m/s.
So would electrons (in a Cooper pair) travel around the loop at this ...
- 5,925
2
votes
0
answers
93
views
Current between supeconducting rings
How to calculate the current between two superconducting rings with radius r separated by a distance d?
Please note that being unfamiliar to the concept of superconducting rings, I can't approach ...
- 21
2
votes
0
answers
817
views
Skin effect and currents
Here in this picture
you can see $I_W$ which is induced by H.
But why $I_W$ is not vice versa?
Because of
$$rot \, \vec B = \mu_0 \, \left( \varepsilon_0 \frac{\partial \vec{E}}{\partial t} + \vec j \...
- 919
1
vote
0
answers
26
views
Understanding if possibly current density can be made scalar by changing the current definition?
In the accepted answer to this question : Why does current density have a direction and not current?
I understand the need for current density to be vector, but I am now curious if the definition of ...
- 235
1
vote
0
answers
25
views
Find the external work for getting the wire from $\infty$ to the current location. (the potential in $\infty$ is $0$)
A ball of radius $R$, with charge density:
$$\rho(r)=\beta r,\quad\beta > 0$$
A thin wire, with charge density: $\lambda[\frac{c}{m}]$ and length $R$, located between $x=2R$ and $x=3R$.
My ...
- 121
1
vote
2
answers
259
views
Does a higher voltage always mean a higher electric field strength?
In a step-up transformer, the output voltage is higher than the input voltage, while the output current is lower than the input current. Basically, since P = VI is conserved, the current has to ...
- 337
1
vote
1
answer
24
views
In applications where heating is not the required from of energy, current is to be kept low as per Joules law. What energy is considered useful?
As per this paragraph from Wikipedia
"Joule heating is referred to as ohmic heating or resistive heating because of its relationship to Ohm's Law. It forms the basis for the large number of ...
- 11
1
vote
2
answers
147
views
On a nanoscopic level, what really happens to the electrons in the secondary coil of a step-up transformer?
I know that when AC is passed through the primary coil of a step-up transformer a higher emf is induced in the secondary coil (with more turns) of the transformer. Since energy is conserved, and P = ...
- 337
1
vote
0
answers
23
views
In AC, do Electrons move in perfect Sync with Generator Rotation across the whole distance?
While i'm self studying electricity, one interesting topic seemed counterintuitive to me, which is:
When an AC generator connects to a long XX KM length cables; each cycle, the electrons in the cables ...
- 11
1
vote
2
answers
3k
views
Transformers: How does current in primary coil change?
I was doing a question on transformers and found this really confusing question:
A 100% efficient transformer converts a 240V input voltage to a 12V
output voltage. The output power of the ...
- 11
1
vote
0
answers
33
views
Drift velocity of electrons how electrons drift
When no external electric field is applied, electrons move with thermal velocity and return to their initial position so displacement is zero. However, when an external electric field is applied, ...
- 11
1
vote
2
answers
131
views
Current flowing inside battery/voltage source
Current is the flow of charges (many say electrons).
Do these charges flow just between the terminals of the source/battery (terminal to terminal) ?
Or
Do these charges flow through/inside the ...
- 1,441
1
vote
1
answer
287
views
Is there a potential difference across the bulb after current passed through a diode?
I understand that voltage can exist without current so what I want to ask is will there be a potential difference across the bulb(situated after the diode) when a batteries supplied energy through a ...
- 113
1
vote
0
answers
159
views
Electrical resistivity calculation of a cylindrical material
I have a copper rod, its diameter is 13mm, and its height is 13mm. I want to check its electrical resistivity. I have tools to give this copper a constant current by two points (the two black dots in ...
- 111
1
vote
2
answers
117
views
Why do generators need a complete circuit to move electrons but capacitors do not?
A charged capacitor will shock you if you come too close to it or touch it, and you are connected to the ground. A generator will only generate electricity if it has a complete circuit, it cannot just ...
- 615
1
vote
0
answers
129
views
Conductivity and free/bound charge for conductors, insulators/dielectrics and semiconductors
I am slightly confused about the distinction between these three types of material in terms of
a) conductivity
b) the idea of free and bound charge
If we consider the distinction between these in ...
- 3,997
1
vote
1
answer
97
views
Does the Conventional Current flow consist out of anything? (virtual photons)
I've red that virtual photons are a way of interpreting the electromagnetic force between charged particles. Is convention current a electromagnetic field or force? Or is it a movement of ...
- 15
1
vote
0
answers
148
views
Dangers of AC currents at different frequencies.
I'm trying to understand the dangers of different types of electrical currents. This question has been answered quite well but in reference to the above image I found here AC current at very high ...
- 111
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
1
vote
0
answers
126
views
How to apply kirchoff's laws to motors in DC and AC settings
DC case:
is it ok to treat a motor as a variable resistor, with resistance depending on the load?
AC case:
suppose I have a motor that runs at 120V AC and is rated to X watts, how can I determine how ...
- 215