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Questions tagged [capacitance]

The ability of an object to store electric charge.

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1answer
14 views

Polarized Vs Non-Polarized Capacitors

I am wondering what makes a polarized capacitor physically different than a non-polarized capacitor. I am aware they are functionally different. I understand the physics of a non-polarized capacitor, ...
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2answers
182 views

Trying to understand the electric potential and potential energy

I am trying to understand some facts on electrical potential and potential energy. It is quite confusing in the text to say that the zero potential could be freely chosen for convenience. In that case,...
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1answer
9k views

Derivation of the capacitance of a cylindrical capacitor

I have started learning about the capacitance of the capacitors of various geometries from my textbook. While calculating the capacitance of a parallel plate capacitor, the formula $$ V_f-V_i=-\int^...
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2answers
60 views

RC circuit series and parallel [on hold]

R and 2R are in parallel. 4R and 3R are in parallel. I dont know where to go after calculating the the parallel Rs. Do you become in series? If so, how? It is right after the switch is closed. So ...
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1answer
285 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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0answers
28 views

Series LC circuit capacitive frequency control [on hold]

if I had a series LC circuit with an air core inductor and a varyable capacitor (whose capacitance can be varied by a large margin) could I in theory be able to drive my resonator across a wide range ...
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0answers
19 views

Capacitance of two parallel cylinders of finite length

I've got some big troubles calculating the capacitance of two parallel cylinders of finite length. If the cylinders are infinite everything is fine but I need an excat solution or at least a good ...
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2answers
610 views

Express Laplace transform of voltage across a capacitor in terms of charge

In Charge Tunneling Rates in Ultrasmall Junctions section 2.1, the authors consider the problem of charge relaxation in a simple circuit shown in Figure A. The implicitly use an assumption made about ...
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1answer
22 views

How can a charged hollow sphere induce charge on a neutral conducting sphere kept inside it?

In case of a charged conducting hollow sphere charge resides on the surface and the field is radially outwards or inwards depending on the charge.Due to the symmetric consideration field inside the ...
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6answers
74 views

Telling if Capacitors are in Parallel or Series

So C1 and C2 are in series. But if each one is placed in red boxes, they are in parallel? It's confusing going jumping between current, capacitors, and resistance. For me it's kinda confusing ...
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2answers
121 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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0answers
18 views

Motion of dielectric inserted between plates of parallel plate capacitor [closed]

If a dielectric is inserted between the plates of a parallel plate capacitor a force will act on it, so will it oscillate or not? Two cases would be considered: 1: battery not connected 2: battery ...
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1answer
773 views

Theoretically speaking what are the limits for super-capacitors in terms of their storage capability?

According to wikipedia, commercially available super-capacitors in 2010 can store 30Wh/kg, with 85Wh/kg achieved in a lab in 2011. Have any theoretical calculations been done to show what can be ...
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4answers
93 views

Internal resistance and Instantaneous current?

Okay, this would probably seem a pretty basic doubt but I can't understand this thing. I know that when the current is not flowing in the battery the voltage across the terminals is the emf of the ...
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1answer
24 views

Question on capacitance between two parallel cylinders

We are asked to prove that the capacitance of two infinitely long uniformly charged conductors with coaxial cylindrical surfaces is given by \begin{equation} C= \dfrac{2\pi\epsilon_0L}{\mathrm{ln}\...
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2answers
382 views

Force on plate of parallel plate capacitor with dielectric

If we have a parallel plate capacitor whose charge is +Q and the polarization charge as Qp as shown in the figure.. then while finding the force acting on the left plate of the capacitor for instance,...
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0answers
25 views

What is the Potential difference in $C_1$? [duplicate]

I can not seem to figure this out. My try so far: put C2 and C4 as C' by parallel put C' and C1 as C'' by series Finally, Put C'' and C3 and C5 as Ct by series find Qt by Qt=Ct*V after finding the ...
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1answer
15 views

Electric field in capacitor arrangement with different dielectric media

Please consider the following arrangement of infinitely extended charged plates. In z-direction the system also extends to infinity. The charged plate in the middle of the figure is 2x negatively ...
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2answers
23 views

What is it that drives the electrons from one plate to another through a battery in a capacitor?

The situation is as follows: You have a parallel plate capacitor, disconnected from a battery on both ends. We know the battery tries to maintain a constant potential difference between its two ends. ...
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1answer
363 views

Inductor vs. capacitor discharging - how a low resistance affects the two?

I'm confused about why the two discharging patterns occur in regards to resistance. If I am understanding correctly: An inductor: A lower resistance means that it will take longer for the inductor to ...
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2answers
1k views

Does connecting a capacitor in parallel with a wire “short” it out?

I have a question about capacitors. In the circuit below, capacitor C2 is in parallel with a wire. When a resistor is connected in parallel to a wire, the potential across it equals zero so no current ...
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4answers
57 views

Current when capacitor and resistor placed in parallel?

If the question is too long please comment to shorten it atleast , I really need an answer. I have just started learning about RC circuits and these circuits are confusing me.My questions-1)What will ...
2
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0answers
84 views

A pendulum connected to a capacitor [closed]

A mathematical pendulum of length L whose rod is made of a conducting material moves so that its inferior end slides without friction on a metallic support in the shape of an arc of circle. The rod ...
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1answer
31 views

Charges on conductor

So i was reading an answer to question Why are the two outer charge densities on a system of parallel charged plates identical? Points that I didn't understand that how come -Q1+x charge can get ...
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3answers
72 views

Is a complete circuit required for capacitors to redistribute charges?

Suppose I have two capacitors of different capacitance $C_1$, $C_2$and they have been charged prior connecting by voltage of $V_1$ and $V_2$ respectively the positive plate of one capacitor is ...
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0answers
26 views

Connecting one lead of capacitor to a certain charged object (to get a potential difference)

Setup-A charged sphere , connected to one plate of capacitor , other lead of capacitor is free. Question-Will the capacitor plates go through a charge redistribution ? Arguments/Counterarguments-I ...
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1answer
233 views

Does an electron change the electric field in a parallel plate capacitor?

We know that the normal electric field direction in a parallel plate capacitor normally goes from the positive plate to the negative plate, so going from a high potential to low potential. Thus, if we ...
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0answers
29 views

How to use energy conservation in following case [duplicate]

A capacitor of capacitance C is intially uncharged is connected with a battery of emf ε.Find the heat dissipated in the circuit during charging?How can we apply energy conservation although there are ...
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2answers
49 views

How do we extract energy from capacitors?

I have an intuitive reasoning for the use of capacitors. I think that it is used to store electrical energy. Without going in much detail in engineering and being at an introductory level of ...
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0answers
17 views

Is the potential difference across any capacitor equal for n identical capacitors connected in series? [duplicate]

(https://i.stack.imgur.com/Pfit8.jpg) Is the potential difference equal for n identical capacitors connected in series? Please go through the image as my confusion lies there.
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1answer
31 views

How does the stud finder work?

My textbook explains how a type of stud finder works by an illustration. What I can’t understand is how does the piece of wood have an effect on the capacitance of the plates when it is so far away ...
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2answers
48 views

Impedance of an LCR circuit

So I am trying to understand how to find the impedance of the parallel LC component of this filter circuit. I am given that the transfer function $\mathbf{T}_C = \dfrac{\mathbf{V}_{out}}{\mathbf{V}_{...
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1answer
229 views

Capacitance dependence on separation between plates

I know that the capacitance of a parallel plate capacitor is $C = \frac{\varepsilon S}{d}$. I am supposed to perform a linear regression to obtain $\varepsilon$, however it turns to be a quadratic ...
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3answers
56 views

Why is the force required to keep a parallel plate capacitor EQ/2?

In our electrostatics course we were talking about how if you increase the separation of the plates by a tiny amount, then as the field is still constant, the potential difference increases. This ...
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1answer
235 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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4answers
1k views

Why is there no current between two capacitors connected in series?

I want to ask a question about the figure below. Why the current does not flow from $-Q$ term to $+Q$ term or from a to b since there is a voltage?
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2answers
66 views

Does Kirchhoff's rule break down as it applies to capacitors

A homework problem asked me to find the voltage across a series of capacitors after they came to equilibrium. Essentially a capacitor C1 with a capacitance of 6.0 F is charged until the potential ...
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5answers
83 views

If current through a resistor is zero, does the circuit break?

I'm really confused. I'm studying about how capacitors are charged, and I learnt that there's a resistor attached in series with the capacitor when it is being charged. When the capacitor is fully ...
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2answers
209 views

Are these capacitors parallel or in series?

I am a bit confused. The authors say these conductors are parallel when the switch is on. But to me it looks like they are in series since the handle is insulating. How can you explain that they are ...
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3answers
63 views

Charging capacitor in an incomplete circuit [closed]

I have 2 confused questions regarding the below circuit. please help me out How will the capacitor even charge in the following scenario when the right side of the capacitor is not connected to ...
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0answers
36 views

Calculating the self capacitance of a rectangular electrode with a dielectric on one side

I am trying to derive an expression for the capacitance of a rectangular electrode with a dielectric material of thickness $t$ and relative permittivity $\epsilon_r$ in contact with one side, sized ...
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2answers
347 views

Resistance and permittivity

I saw this formula in a book RC = ρε Can anyone tell me what is the significance of this formula or how is it derived? The capacitance and the resistivity seem to be pretty much unrelated quantities ...
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1answer
29 views

Conduction current for parallel-plate capacitor

I am reading Sadiku's Elements of Electromagnetics and here is the proof given to show that conduction current = displacement current for parallel-plate capacitor. Displacement current: \begin{align*}...
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1answer
23 views

Repulsive force from charge accumulation in a capacitor plate?

During a charged state of a capacitor (Regardless of the type of capacitor), Simple parallel plate: .png Parallel plate with dielectric material in the gap: ]3 Supercapacitor: How is the ...
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1answer
22 views

Is it possible to create and control a magnetic field in a dielectric material?

A capacitor is usually formed by an insulater between two conductive plates. By applying voltage difference between the plates we create an electric field within the insulator in one direction. If you ...
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1answer
40 views

Electric potential and voltage

A capacitor is connected to a battery with constant voltage. If you approach one of the plate to the other, what happens to electric potential? I already have an answer to this question but it's ...
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1answer
45 views

Neglecting capacitor from circuit

Take a look at this circuit : This question is answered in $Serway$ $7th$ ,And the book neglected 8 Farad capacitor because the voltage between $c$ and $d$ is zero. My questions is : $1.$Should not ...
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1answer
274 views

Maximum stored energy in a capacitor with different materials?

In class today, we saw dielectrics and their application to capacitors (e.g. parallel plate, cylindrical, spherical capacitors). A question came up which discussed how when we have a capacitor that ...
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1answer
26 views

How can we analyze electronic capacitors in series? [closed]

Two capacitors are in series, such as in this circuit diagram: When doing a circuit analysis, how can we describe the voltages and charges across the two capacitors?
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1answer
67 views

Does the voltage of the battery change if you use it? [closed]

If you use the battery to charge a capacitor does the voltage of the battery decrease or still the same? Does the voltage of a capacitor decrease if you use it to charge another capacitor?