Questions tagged [capacitance]

The ability of an object to store electric charge.

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Currents in an isolated metal exposed to an alternating uniform electric field

For example, let's look at a metal sphere between a capacitor's (infinite) plates. Let's run an AC current through the capacitor, resulting in an oscillating electric field. The charges will move in ...
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38 views

Potential of 2 parallel plates

How can I write down a potential of 2 parallel plates (area $A$) with charge $+Q$, $-Q$ such that V(inf)=0 and V(in) is what I would expect, $Ed = Qd/A\epsilon_0$. Do I have to write a discontinuous ...
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60 views

Can Van Allen Radiation belts act as a capacitor?

There are two Van Allen Belts at rougly 5000Km and 17000Km from the surface of the Earth each of them containing majority of one of the charges electrons and protons). Can these belts like a ...
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162 views

Negative charge on capacitor, Kirchoff differential equation with step function

I'm solving a differential equation of the form $$200q'+\frac{200}{3}q=3U_o-6U_6+3U_{12}$$ Where $U$ is the Heaviside step function. $q(0)=0 [Coulombs] $ After solving it, I get that at time $t=18$ ...
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134 views

Energy of moving capacitor

On the following link were a discussion about energy in capacitor moving parallel to its field: Where's the energy in a boosted capacitor? My question is what happen if capacitor is moving ...
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65 views

Capacitance changes by a factor of 3 or 9?

This is an example problem with solution in a book I am reading on electrostatics. "We have two square parallel plate capacitors with length $a$ and separation $d$ with $d<<a$. If we triple ...
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85 views

Charging a spherical capacitance

How could one charge a spherical capacitor with a battery or any other emf source?
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496 views

Does the Fringe effect occur in capacitors in the interdigitated form?

I am currently doing my undergrad dissertation on graphene supercapacitors. I have read that the fringe effect is a well established phenomenon on parallel plate capacitors, but does it also occur in ...
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132 views

What is the electrical field of a capacitor plate as a charge approaches

The electrical field for a charge density $\varrho(r)$ is $${\bf E}({\bf r})=\frac{1}{4\pi\varepsilon_0}\int \varrho({\bf r}')\frac{{\bf r}-{\bf r}'}{\hspace{.1cm }|{\bf r}-{\bf r}'|^3} \mathrm d^3r'....
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29 views

Grounded plates and induced charges

This is from Jewett's "Physics for Scientists and Engineers", problem 26.58, if you have the book: Two large, parallel metal plates each of area A are oriented horizontally and separated by ...
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78 views

Electric field in capacitors

As many of you may know, a capacitor stores energy by means of the electric field crested between the plates of this capacitor, but how is the electric field able to store the energy itself?
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204 views

Amount of energy that can be stored from Faraday flashlight / linear alternator?

You'll have to forgive me if this question is either extremely elementary or does not make sense — I am a civil engineer with little E/M physics background beyond high school education. I am working ...
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Charge in the each capacitor when connected in parallel

Consider a situation where we have three capacitors of capacitances A, B and C connected in parallel to a battery of emf V. The equivalent capacitance of the combination would be A + B + C. The ...
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57 views

Are electric fields constant in the dielectric materials of a parallel plate capacitor?

For every example I've seen this was an assumption I have made. However with this example, I am unsure. Either the electric field is constant through the e1 dielectric meaning e2 and e3 must be equal, ...
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88 views

What does the potential of a charged conductor mean?

While studying the unit of electrostatics, I came across the formula $$C=\dfrac QV,$$ Where C refers to the capacitance of the conductor, $Q$ refers to the charge present on the conductor and $V$ ...
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70 views

Energy stored in the battery of a circuit (single electron box)

Consider the following, a closed loop circuit with two different capacitors in series plus a battery that provides a voltage $V$ (in series with the capacitors). You may add a resistance if that helps....
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458 views

Discharging a LC(R) Circuit

Reading through my lecure script I encountered this example which I don't quite understand: Given is the following Circuit: At time $t= 0$ the circuit is closed, before that the circuit was open, ...
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1answer
357 views

Electric energy density

The electric energy density for a parallel plate capacitor is $\frac{1}{2}\varepsilon E^2$ where $\varepsilon$ is the dielectric constant and E is the magnitude of electric field. In my textbook it ...
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1answer
709 views

dielectric slab inserted into constant charge capacitor

I derived the equation for the force $F$ acting on a dielectric of dielectric constant $K$ being inserted into a constant voltage (connected to battery) parallel plate capacitor of capacity $C$, ...
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1answer
435 views

Gauss Law use in an example question

In the textbook (Modern Physics for Scientists and Engineers by Douglas Giancoli) it asks for a capacitance calculation. However, I want just the explanation of the electric field calculation between ...
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417 views

Charge distribution in series combination of capacitors

its a normal series combination of capacitors,only the inner plates are placed differently,one in the beginning and one in the middle,will it not alter the charge distribution ? that is if we will ...
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1answer
536 views

What book will help me understand Electric Circuits?

I have a problem having a clear picture when it comes to solving electrical circuits. I am talking about complex circuits which contain Inductors and capacitors . The methods introduced are clear to ...
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1answer
241 views

Connecting spheres of different capacitance

If I connect a sphere of capacitance $C_1$ to a charged sphere of capacitance $C_2$, will the charge be distributed evenly on both spheres (is the charge density going to be equal on both spheres?). ...
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1answer
2k views

No change in voltage in a capacitor

While trying to solve this question: Photo copy of the question and answer: Question:On charging a parallel plate capacitor to potential V the spacing between the plates is halved and a dielectric ...
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2answers
51 views

If electric field outside a parallel plate capacitor is zero then how does it stop charging after some time?

Many sources state that “charging of a capacitor stops when potential difference across a capacitor is equal to that of the battery”. But I cannot understand how this is the reasoning as, an electron ...
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96 views

How to simplify such structures to calculate equivalent capacitance?

I am self studying electrostatics for competetive examinations but there is this series of questions demanding equivalent capacitance and I direly need a intuitive understanding of these situations.
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865 views

What happens in the RC circuit when being charged?

Say I have this RC circuit and at the start, the switch is off (current going from left to right and the starting point is just above the battery). I understand that then the capacitor acts just like ...
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254 views

Why the electric field inside a capacitor isn't nul?

I have a doubt regarding this point, i know that the electric field inside a conductor is null, and the capacitor is made by two conducting plates, so what s the point here?
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charging of a capacitor

while charging the plates of a parallel plate capacitor by a battery,i have seen in books that the positive charges remain only on the right side of the first plate what is connected to the positive ...

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