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
366
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
221
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
851
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
718
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 ...
- 1,640
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