Questions tagged [capacitance]

The ability of an object to store electric charge.

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Kirchhoff's Voltage Law does not hold for a free source RC circuit?

Say I have a simple free source RC as depicted in the image below. The capacitor initially has a charge of Q on its positive plate and at time t=0 the switch is close. I use the mesh current as shown ...
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138 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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Does the dielectric constant changes as the voltage is applied in every dielectric material?

As the voltage is applied at both sides of the dielectric material(ex. front surface +5V and rear surface 0V), the energy is stored in the material, right? I heard it's because the dielectric ...
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Electric Field in Capacitors with Dielectrics in them [closed]

The space between the plates of a charged parallel plate capacitor is shared by two different slabs of same dimensions in a parallel connection . What should the ratio of electric field in the slabs ...
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32 views

New interpretation for Heat in Resistanceless Capacitive Circuits

I have been studying RC circuits and noticed that even in a resistanceless circuit, when a capacitor is charged by a constant potential difference source, there is considerable heat generation, equal ...
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2answers
55 views

A theoretical question about matter/antimatter and capacitors

Let's assume that the experiment is done in a vacuum and there's a circuit as in the attachment. The values of voltage/resistance/capacitance are insignificant. Assume that the right terminals of ...
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43 views

Maximum Charge on the Capacitor [closed]

Question: A square loop containing an inductor of inductance $L=4 ~H$ and a capacitor of capacitance $C=2~ F$, is fixed in the plane of wires (infinitely long) carryinig time varying current $I_1=4t~ ...
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23 views

Calculating electric current between capacitors [closed]

A capacitors in a shape of a disc with radius $ a $ and a distance between the discs of $ d $ are charged with $ Q $. at $ t=0 $ we put conductive material with resistivity of $ \rho=\rho_{0}\frac{r}{...
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121 views

Capacitor Discharging through a fixed resistor

When a capacitor discharges, the pd across it goes from V0 to 0 in a given time. But when you look at the pd across the fixed resistor, this too decreases from V0 to 0. So we can say Vcapacitor=...
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43 views

Why do the two plates of a capacitor store equal amounts of charge?

I understand that this happens due to Kirchhoff's law. Any current entering one side of the capacitor must have come from another part of the circuit connected to the other side. But is there an ...
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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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Is my understanding of the process of charging a capacitor correct?

Suppose, I have a parallel plate capacitor with copper plates $A$ & $B$ connected to a battery. Plate A is connected to the negative terminal of the battery and plate B is connected to the ...
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475 views

What is capacitance, in general?

In circuit analysis software capacitance can be measured between any two nodes of a circuit or of a multiterminal device. In practical terms we take $C_{ij}$, the capacitance between $i$ and $j$ as ...
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700 views

Charged dieletric/conductor in capacitor

It is a standard problem to consider a dielectric or a conductor between the parallel plates of a capacitor. But what happens to capacity, voltage, charge, inserting between the plates of an ideal ...
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2k views

Magnetic field in a capacitor

If in a flat capacitor, formed by two circular armatures of radius $R$, placed at a distance $d$, where $R$ and $d$ are expressed in metres (m), a variable potential difference is applied to the ...
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861 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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How does humidity affect the dielectric constant of a material?

I'm trying to figure out how a humidity sensor using a Capacitor works, and every document I have managed to find seems to come to the conclusion that an increase in humidity causes the capacitance to ...
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28 views

Finding charges on the plates of a capacitor system connected to a battery

Five identical capacitor plates, each of area A, are arranged such that the adjacent plates are at a distance d apart. The plates are connected to a battery of e.m.f. E volt as shown. The charges on ...
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415 views

Adding a capacitor in parallel improves power factor of an inductive circuit?

I know that to reduce power loss during transmission, we require a power factor as close to one as possible. This can be done by making $Z$ tend to $R$ which can be done by increasing $X_c$ such that ...
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1answer
46 views

Maximum charge of a capacitor

Suppose we have a capacitor charged with charge $Q1$ Then an electron beam hits the positive plate of the capacitor, thus increasing the charge of the capacitor (the battery will begin to deposit the ...
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1answer
32 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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Capacitance of two non parallel plates

What is the formula for capacitance of two non parallel plates at an angle with each other?If the plates were parallel then the value can be calculated as (PermittivityX area of one plate)/distance ...
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2answers
53 views

Are resistors, inductors, capacitors the only possible passive components in this universe?

I wonder whether or not there is a possibility to find another passive component (with value either $X$ or $Y$) that will change the well known RLC circuit equation below $$ L\; \frac{\mathrm{d}^2 \; ...
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Find a formula for the current after $t$ seconds, given that the voltage is initially $0$, and a constant current of value $k$ is applied [closed]

V= 1/C ∫ I dt, where I is the electric current, V is the voltage and C is the capacitance. Find a formula for the current after t seconds, given that the voltage is initially 0, and a constant ...
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1answer
323 views

RC circuit: is order of resistance and capacitor important?

in a RC circuit is order of resistance and capacitor important? Typically there is the battery then the capacitor then the resistance, but is it ok if I draw with the battery then the resistance and ...
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1answer
33 views

Force required to insert dielectric in a capacitor connected to a battery [duplicate]

This is a sum in a reference book( H.C. Verma, concepts of phycics). A dielectric slab is being inserted in a parallel plate capacitor as shown in the diagram. The width of the plates is given to be $...
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1answer
48 views

Where is energy dissipated on charging a capacitor? [duplicate]

The energy lost on charging a capacitor can be easily found from the change in energy of the components of the circuit and the energy supplied by the battery. On charging a capacitor I know that the ...
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213 views

Fringing of electric field

I have read that in a capacitor with charged parallel plates the electric field lines are parallel in the middle, but they tend to bend outwards (causing a "fringe") towards the ends of the ...
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Self-energy of a conducting shell when we put some charge inside it

We already know that if we have a conducting sphere with total charge $q$, then the self-energy of the sphere is $\frac{q^2}{8\pi\epsilon R}$, where $R$ is the radius of the sphere. But my question is,...
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529 views

Capacitance of a 2D capacitor

I would like to know how to calculate the capacitance of a 2D capacitor and the derivation of the formula. I have been looking all over the place but could not find an answer to this. Thank you!
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41 views

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 ...
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62 views

Why is the time constant of RC circuits calculated the way it is?

I learnt about the basics of RC circuits, taking a simple case of only a resistor and a capacitor connect in series to a battery. But following this I faced several questions which involved a more ...
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Time constant of $RC$ circuit with more than one capacitor [closed]

Suppose I have three circuit components - two capacitors of capacitance $C$ each and a resistor of resistance $R$, all of which are connected in parallel. The resistance across any individual ...
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501 views

Current in a RC circuit

In order to find current in an RC circuit, resistance of only the resistor is considered i.e. $I_\text{resistor} = V_\text{resistor} / R$. Why is the reactance of the capacitor not considered? The ...
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31 views

Time-domain model of a capacitor when the capacitance is varying with time

The current through a capacitor as a function of time is given by; $$i(t)=C\cdot \frac{d}{dt}U(t)$$ When assuming that the capacitance $C$ does not vary with time. But what if it does? I don't know ...
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215 views

RC circuit discharge while being connected to a battery?

I am facing a conceptual problem in analyzing the following situation which was part of a physics exam: A series RC circuit with $R = 200k \Omega$ and $C = 10 \mu F$ is connected to a 5V battery and ...
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Leyden jar-How does the storing process work?

We can view the Leyden jar as a capacitor and a dielectric (glass). When the metal parts are charged thus is due to influence in the dielectric a counter electric field to be found.When we separate ...
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175 views

Does $\int{\frac{1}{dx}}$ have any meaning in physics?

Recently I came across this problem : There are two identical parallel plates of length $L$ and breadth $B$ on the XZ plane . One plate passes through $Y = 0$ and the other passes through $Y = d$. ...
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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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Fringe Fields in a Cylindrical Capacitor v/s Parallel Plate Capacitors

I understand that Fringe Fields exist on the edges of a parallel plate capacitor like so: I was trying to figure out if a Cylindrical Capacitor would have fringe fields as well, and how they would ...
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118 views

LCR circuit (AC source) potential difference across capacitor

For a LCR circuit connected to AC source of emf$$E= e\sin(ωt)$$ and let the current in LCR circuit be I then $$I=i*\sin(ωt+Φ)$$ then it is given that potential drop across the capacitor is V.ie$$V=-...
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221 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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How does a Capacitor generate a potential difference even after disassembling the Capacitor?

I saw a video of Walter Lewin on YouTube in which he was showing a demonstration on Capacitors. In this demonstration, he gives a charge to the Capacitor, dissembles it and reconstructs the Capacitor. ...
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118 views

What does energy stored in an electric field mean?

I know this question has been asked twice before, but i didnt find any satisfying answer there. I learnt in my class that the energy stored in the capacitor per unit volume comes out to be $\dfrac{\...
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27 views

How does charge gather on both plates of the capacitor?

In my textbook, it states that when a parallel-plate capacitor is connected to a battery, charge will flow from the battery onto both plates. How is this possible since current only flows from one end ...
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213 views

Common potential in Capacitors

If two isolated charged capacitors (of different capacitance) are connected in parallel to each other they acquire a common potential. But suppose if i connect positive plate of one capacitor to ...
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26 views

Can current flow through a capacitor submerged in electrolytes?

Imagine two flat conducting plates (3 x 3), one as the anode and the other as the cathode, submerged into electrolytes (e.g. sea water) and a DC current is applied to this apparatus. Could current ...
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248 views

Capacitors in parallel and capacitors in series

How can I recognize clearly when I deal with capacitors in parallel or capacitors in series? Can follow a "rule" or a intuitive method? I have to do difficult exercises regarding system of capacitors ...
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267 views

Derivation of Energy Stored in a Capacitor

I was looking at the standard derivations of the energy stored in a capacitor, and any that I find seem to begin with the following or a similar integral: $$W=U=\int_{Q=0}^{Q_f} \phi \, dq $$ Which ...
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Why can rolled up capacitors be modelled as flat parallel plates?

If you have two parallel plates of opposite charge with a dielectric in between, then Capacitance $$ C = \dfrac{A \epsilon_{0}}{d} K$$ Where $ K $ is the dielectric constant. This is used to calculate ...

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