All Questions
21
questions
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How does capacitance of a capacitor not depend on the distance of the capacitor to a battery?
When you consider the positive terminal of battery, wire and capacitor plate, they form a single conductor, which is polarised by the field of the other capacitor plate, but it is not polarised as ...
- 155
0
votes
0
answers
61
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Total capacitance from a capacitance matrix
I am currently doing a project where I need to find the capacitance of a multi-conductor system. Through my literature review, I read about the concept of a capacitance matrix. After more research, I ...
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
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
1
vote
1
answer
151
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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 ...
31
votes
10
answers
8k
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How is energy "stored in an electric field"?
My physics teacher told me the statement "The energy of a capacitor is stored in its electric field".
Now this confuses me a bit. I understand the energy of a capacitor as a result of the ...
- 492
-1
votes
1
answer
75
views
What is electric permitivitty?
I have read 10 different explanations for this in 10 minutes. By definition, to permit means to allow something, but some sites say that it is actually how much a material resists the electric field?
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- 183
14
votes
9
answers
8k
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What happens if you use a battery to charge up a capacitor fully, and then disconnect the battery, where does the charge 'go'?
The title says it all really, but I think that since the battery is disconnected there is now an 'open circuit'. I know that charge can only flow if the circuit is complete (closed).
But the part that ...
- 640
1
vote
2
answers
128
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Is the work done in separating electron from neutral atom stored in its electric field?
This particular thought crossed my mind while deriving the expression for energy density of electric field in parallel plate capacitor.
Energy density= $\frac12 \epsilon E^2$
It appears to me that ...
- 1,568
-1
votes
1
answer
45
views
What is the effect of the energy stored in a capacitor on the current it supplies? [closed]
For say, what would be the difference between two capacitors with the same capacitance only one storing 0.5 joules and the other one 1 joule.
0
votes
1
answer
337
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For which reason do we say that the charge surface density is rougly constant (uniform distribution) on a capacitor's plates?
Consider for instance a parallel plate, a spherical or a cylindrical capacitor. Usually we analyze it by considering the surface charge density on each plate uniform, i.e. constant along the plate.
...
- 1,319
1
vote
1
answer
696
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Why is the field inside a capacitor not the sum of the field produced by each plate?
In this answer by David Z, we can read,
When discussing an ideal parallel-plate capacitor, $\sigma$ usually denotes the area charge density of the plate as a whole - that is, the total charge on the ...
- 1,292
0
votes
1
answer
152
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$E$-field between dielectric and plate in parallel plate capacitor and Feynman's claim
Feynman says about $E_{0}$ below
Note that the field $E_{0}$ between the metal plate and the surface of the dielectric is higher than the field $E$; it corresponds to $\sigma _{free}$ alone.
$\...
- 1,292
0
votes
1
answer
42
views
Capacitors and voltage rating
Imagine a battery that creates a +9000V Potential difference in respect to ground (The Earth) in it's positive terminal. (The Earth is at 0V in this example)
And a +8992V potential difference in ...
- 323
2
votes
2
answers
263
views
Charge decay (leakage) of a charged metallic sphere
I have a spherical ball (charged to a specific charge) and the charge on the ball leaks to the surrounding. I observe that the charge on the ball reduces exponentially. Can anyone give a theoretical ...
- 21