All Questions
Tagged with electromagnetism capacitance
241
questions
2
votes
5
answers
109
views
Magnetic field in a capacitor in a $LC$ circuit
Consider a simple $LC$ circuit in which the charge on the capacitor varies sinusoidally. Current flows in this circuit, changing the charge on the capacitor and hence changing the electric field ...
- 29
1
vote
1
answer
780
views
Trying to understand how to apply Maxwell stress tensor to calculate forces
I'm struggling to understand how to use Maxwell's stress tensor to compute electromagnetic forces acting on surfaces. I'll take problem 8.7 from Griffths Introduction to Electrodynamics as an example.
...
- 171
3
votes
1
answer
342
views
Doubt regarding a possible mistake in Griffiths Electrodynamics
Griffiths, in section 7.3 Maxwell's Equations, says:
There’s another way to see that Ampère’s law is bound to fail for nonsteady
currents. Suppose we’re in the process of charging up a capacitor (Fig....
- 702
1
vote
1
answer
29
views
Corona Discharge, Leyden Jar and Free Charge [closed]
Watching Walter Lewin's 8.02x- Lect 14, at the end of it, he explains the mechanism behind a Leyden jar. The (simplified) picture is the following:
Source: https://www.youtube.com/watch?v=By2ogrSwgVo
...
- 115
2
votes
0
answers
42
views
What if two plates charged with different charges are placed face to face?
I'm asking this question because I can't solve it even if I ask a lot of smart people. (Please understand that I don't speak smoothly because I use a translator. I'm korean student..)
In the next ...
- 21
0
votes
1
answer
77
views
Capacitance matrix is diagonally dominant
I have heard of the following claim “the capacitance matrix of an isolated system of conductors is diagonally dominant” but I couldn’t find a way of proving it myself or any reference for that matter. ...
- 402
1
vote
2
answers
358
views
Relation between resistance, capacitance and resistivity
I recently learnt that for a resistive medium, $RC = ρε$ where $R$ is the medium's resistance, $C$ is the capacitance, and $\rho$ is the resistivity. Now, I am able to prove that this is true in the ...
- 301
1
vote
1
answer
29
views
Charging capacitor moving with respect to the dielectric
Suppose I am charging a capacitor, so that a magnetic field is generated. This capacitor is placed inside a dielectric material with permittivity $\epsilon$ and then it is moved parallel to it's ...
- 49
1
vote
0
answers
105
views
Capacitance of a System of Two Spheres
To explain more clearly, I am looking for how one would derive an expression for the capacitance of a system which consists of two conducting spheres of radius $a$ separated by a distance $d>2a$. I ...
- 11
4
votes
5
answers
2k
views
Can you charge a capacitor with only voltage (without current)? If No, then how does a capacitor correct power factor?
Let me explain you why I am asking this question.
The other day I was studying about power factor correction of a (step up or any) transformer. It said that on the output side of transformer's ...
- 129
0
votes
0
answers
83
views
How do you determine the electromotive force when the negative plate of the capacitor is connected to the positive terminal?
$\newcommand{\d}{\mathrm{d}}$We have a square wave source with period $T$ and voltage $V_0$ connected to a circuit which is has a resistor of resistance $R$ in series with an uncharged capacitor of ...
- 221
0
votes
1
answer
51
views
Enhanced capacitance by magnetism?
Consider the first picture.
This is much like a parallel plate capacitor charged by a battery. But instead of parallel plates we are using parallel rings. The rings are attracting each other because ...
1
vote
0
answers
40
views
Why do two infinite planes contribute to Electric Field but not two surfaces in co-axial cylinder
I understand why the electric field between two infinite planes is $\frac{\sigma}{\epsilon_0}{\vec{e_z}}$. Both planes contribute to the field - the upper positive charged plane "pushes" ...
- 149
1
vote
1
answer
151
views
Does a spherical capacitor hold as much energy as a spherical shell?
Consider a spherical capacitor, that is, two concentrical spherical shells which serve as plates. Suppose the capacitor is charged. It is my understanding that the energy stored by a capacitor is ...
3
votes
0
answers
194
views
Wave equation derivation in a transmission line
$$
V(x, t) = L\Delta x\frac{\partial I}{\partial t}(x, t) + \frac{1}{C \Delta x}\int{I_c(x, t) \; dt} \tag{1}
$$
$$
V(x + \Delta x, t) =\frac{1}{C \Delta x} \int {I_c(x, t) \; dt} \tag{2}
$$
$$
I(x) = ...
- 1,525