Questions tagged [capacitance]

The ability of an object to store electric charge.

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34 views

Wouldn't extra surface area from a thicker active material layer in super capacitors be more important than minimizing the gap distance

Capacitance is proportional area, and inversely proportional to gap distance. I've read all over the internet that you need to make capacitors have as small a gap distance as possible, but I wonder if ...
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129 views

Charge density on a capacitor plate

Is charge uniformly distributed on a capacitor plate? For a conductor, charge density is more at sharp ends. So, shouldn't charge density be more on the corners of the plate?
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81 views

If you would replace ITO, would it ideally have a lower or higher relative permittivity?

ITO is used as the conductive layer in a touchscreen. If you would replace ITO in a capacitive touchscreen, would it ideally have a lower or high relative permittivity? The relative permittivity (...
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132 views

What causes resistance when moving parallel plate capacitor plates?

The electric field is perpendicular to the direction of the movement, so the vector product is zero, and thus the force should not exist. What causes it?
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118 views

Calculating Electrostatic Energy from Capacitance Matrix

Let's say I have two spherical conductors and I put some charge on each. As I understand it, the electrostatic energy $W$ in the fields will be equal to $$W = \frac{1}{2}C_{11}V_1^2 + \frac{1}{2}C_{22}...
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How to know the values of $R$ and $L$?

Yo there! I have a RL circuit in the arrange showed in the image. Ok, the trick is how can determine the values of the components based on the graphics of a step and impulse response, I detail the ...
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56 views

What causes the double layer in supercapacitors?

I know that the potentials on the supercapacitor electrodes will attract opposite charges in the electrolyte thereby forming a double layer. This double layer acts as an insulator to prevent current ...
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78 views

Can a statically charged object flying in an airplane float?

Lets say you are flying in a plane headed due west at 1000 km/h (278 m/s) with an altitude of 10km. According to http://www.ngdc.noaa.gov/geomag-web/#igrfwmm, at 10km altitude, Earth's magnetic field ...
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432 views

Electric field created by a battery

If I create an electric field using a battery between two parallel plates and leave the battery connected, will the electric field always exist for as long as the battery lasts, including normal self ...
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423 views

Electrostatic energy of the system

Problem : $(A)$ There are two thin concentric metallic shells of radius $a$ and $b$ $(b>a)$. Inner shell carries a total charge $Q$ and the outer shell carried a total charge $–Q$. Calculate the ...
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22 views

Relyance of plate distance on the capacitor equation

I am studying capacitors and i cannot seem to understand why the increase/ decrease in voltage and distance between the plates would affect the capacitor's abillity to store charge. Can anyone help??
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63 views

Is it possible to get an analytic expression of the capacitance for this geometry?

Here is the geometry I'm talking about: Assume the red rectangle is at some constant potential V, like 10 Volts, and the blue is at ground. We can assume that the rectangles extend infinitely (to the ...
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55 views

May the total charge in a supercapacitor be different using unipolar and bipolar voltage power supply?

Consider a supercapacitor where a Helmoltz double layer is formed at each of the 2 electrodes, which is like having 2 capacitors mounted in series, but with different polarities. The total charge at ...
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859 views

Principle of capacitor

It is said that second conductor reduces the potential of fist conductor and hence increases charge taking ability of first conductor My confusion... As per my limited knowledge it is electric field ...
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87 views

doubt from capacitance and capacitors

Can a charged capacitor mathematically be represented as uncharged capacitor connected in series with battery of opposing emf ? Please explain with an example
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52 views

Arms of Parallal Plate Capacitor

In case if Parallel Plate Capacitors, is it necessary for the two plates to be equal in length? If yes why? And if they were not equal, what would be the problem?
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Why should we use good conductors as electrodes of a capacitor?

I was asked if and why why should the electrodes of a capacitor should be good electrical conductors. It seemed obvious to me that if I want to form a Helmholtz double layer (because that's what ...
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646 views

How to compute the charge as a function of time in a simple $CL$ circuit?

I am trying to compute $q(t)$ in a series circuit consisting of a capacitor of plate charges $q_0$ and $-q_0$ and an inductor. The switch is closed at time $t=0$. By Kirchoff's Law, $$\frac{q}{C}+L\...
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92 views

How is the capacitor affected?

I know that a capacitor stores electric energy or electric charge and understand how, but I don't understand how the distance and the voltage affects its capacitance (I mean what are the mechanisms ...
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193 views

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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37 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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1answer
152 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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131 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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80 views

Charging a spherical capacitance

How could one charge a spherical capacitor with a battery or any other emf source?
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476 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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77 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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174 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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1k views

Charging capacity and capacitance of a conductor

I know that charging capacity of a conductor is the maximum charge a conductor can hold And capacitance is the ability of a conductor to hold charge in a given potential . But how are these two ...
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1answer
31 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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1answer
65 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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2answers
236 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
338 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
628 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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425 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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491 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
220 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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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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850 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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227 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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