Questions tagged [capacitance]
The ability of an object to store electric charge.
1,985 questions
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A problem on repeating ladder units (circuital physics) [closed]
To summarise the Q quickly, we basically have a repeating ladder (but made up of finite number of repeating units) and we have to find the value of $C$ (see the diagram) so that the equivalent ...
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Feasibility of Supercapacitor Design Using Etched Brass-Coated Copper Wires [closed]
I'm working on designing a supercapacitor and would appreciate any insights into its feasibility and potential challenges.
Design Overview:
My plan involves creating multi-layer coils where the anode ...
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Can a stable energy system be created using variable capacitors to generate high current for energy recovery?
My idea is:
If two charged capacitors are connected in parallel so that their positive plates are connected together and their negative plates are connected together. Then, if the capacity of one of ...
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How to test $Q = CV$ for a parallel plate capacitor experimentally?
For educational purposes I want to test the formula $Q = CV$ for a parallel plate capacitor (like this) experimentally. My first idea was to use an electrometer amplifier (this one) to measure the ...
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How does the electric field and charge distribution get affected by distance and area in a capacitor?
I've posted 3 question until now two of them got cancelled, hope this one doesn't .
My question is simply why does increasing distance affect the charge distribution on parallel capacitors and shouldn'...
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$LC$ Oscillations [duplicate]
I understand the mathematics behind LC and RLC oscillator circuits in terms of setting up the second order differential equations and solving them, giving us the expected sinusoidal results, but I don'...
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Voltage across Capacitor in Series after shorting internal capacitor
I have what appears to be a very simple question, but I have not seen it asked anywhere and would like to verify my solution is correct. Imagine that you have 3 capacitors in series, each with an ...
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What does $1/C_{eq}= 1/C_1+ 1/C_2 + 1/C_3+\ldots$ mean? [closed]
This question arises from the equivalent capacitance formula in series circuits and i was wondering what adding capacitors in this special addition form mean in the context of series circuits to be ...
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Effect of electric charge on human body
I was reading some other questions when I came up with this.
People are often warned about the danger of electric currents passing through the body. Is charging the human body with a small current ...
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Why do the electric field cross the metal plate (with 2 surfaces)?
First let me tell you what am I talking about, an infinite (just for questions) plane sheet or non-conducting sheet is that have only one surface and we say that the electric field due to it is $$\...
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What will Electric field be when the charge on negative side of Capacitor is changed? [closed]
One of the two parallel metallic plates is uniformly charged with charge $+q$, and the other one is charged with charge $-q$, the electric field between them is $E$. When the negatively charged plate ...
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Op amp as reactive components
Recently I saw a circuit made with op amp and resistors and capacitor which was working as a circuit with "negative capacitance". What does negative capacitance mean? Is it possible to make ...
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Why is "resonance" in these circuits exactly 41.1Hz?
Below is a series resonance simulation where we have 3 circuits with the same components just differing voltage frequencies. The middle circuit has an astoundingly large voltage peak compared to the ...
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Why is $Δω=R/L$ in quality factors derivation?
I was studying the derivation of quality factor and bandwidth regarding what it is. There it was written
$$Q=\frac{\overset{\tiny \blacktriangle}{\omega}}{\Delta\omega},$$
where $\overset{\tiny \...
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Two coupled $\text{LC}$ circuits Kirchhoff's law?
I clearly don't understand something about Kirchhoff's law. For instance, consider this circuit I want to quantise
My guess would be that the voltage loop equations should be
\begin{align}
\text{...
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What is wrong with my derivation of the formula relating the stored energy of a capacitor and its capacity and voltage?
I can't find where I'm doing a mistake here.
Let be two oppositely charged conductors, whose capacity $C= \frac{Q}{|\Delta V|}$ is well-defined. The potential on the positively charged plate is $V_+$ ...
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Battery connected inbetween plates of capacitor
I came across a nice conceptual question on how will things change like potential, capacitance and stored energy if a capacitor is charged by a battery connected in between plates of a capacitor?
Can ...
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Potential energy has been created from no energy
Suppose there are two identical metal plates separated by a certain distance, and a small ball with static electricity is fixed at the midpoint of this distance. For the electric field of the small ...
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Why is charge on a conductor stable? [duplicate]
I know that charge inside a conductor should be zero and because of which all the charge of a charged conductor gets evenly distributed on its surface. But my question is:
If we take a charged ...
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What is the potential energy and kinetic energy for capacitor and inductor?
I always thought that $\frac{CU^2}{2}$ is potential energy stored in a capacitor and $\frac{LI^2}{2}$ is kinetic energy stored in inductor. But here and here (page 12) as understand it correctly for ...
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Exercise (electric field in a dielectric) [closed]
I am trying to solve the following exercise about the electric field generated by a spherical conductor:
"A spherical conductor of ray $R=8cm$ and charged with $Q=8\mu C$ is half contained in a ...
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Why electric field lines inside are parallel inside a cylindrical capacitor? [closed]
Why electric field lines are parallel inside a cylindrical capacitor?
Please help me in this
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Current through points with no voltage drop
I've had a problem with switches in between parallel circuits.
In this textbook question:
The answers state "Note that there is no voltage drop across the voltmeter". However, there is a ...
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A capacitor partially filled with dielectric [closed]
Assume a parallel plate capacitor that was charged up to $Q_0$ from a source $U_0$ and then disconnected from the voltage source. The plates have an area $A$ and the distance between the plates is $d$....
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Energy in Dielectric Medium as a Sea of Dipoles
Simply, why is the energy density in a dielectric medium = $\frac{1}{2}K\epsilon_oE^2$ where K is the dielectric constant of the dielectric medium?
Working proof
Consider a capacitor that is charged ...
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Charging a capacitor without closing a circuit
It might sound absurd but is it possible to charge a capacitor solely by connecting the positive terminal of a battery to one plate of the capacitor and the negative terminal of another identical ...
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Electric field at a point due to dielectric inserted in between a parallel plate capacitor [closed]
Here, I have a parallel plate capacitor with each plate having surface charge density $\sigma$. A dielectric of dielectric constant $K$, is inserted partially between the two plates. What would be the ...
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How will the capacitance of a capacitor reduce when the distance between the plates is increased?
Now I know that if the potential difference between the plates increase that capacitance will reduce, but for that also I thought as the distance between the plates increases, the electric field ...
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Understanding dielectrics on the basis of induced charge and energy density
Simply, why is the energy density in a dielectric medium = $\frac{1}{2} K \epsilon_o E^2$?
For a simple case such as that of a capacitor with a dielectric medium inside it, to find the magnitude of ...
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How can I deduce a capacitance of a capacitor without existing formulaes?
Understanding Charge Accumulation in Capacitors Connected in Series
I've been exploring the behavior of capacitors connected in series and developing a conceptual model to understand how charge ...
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Maxwell stress tensor on a capacitor late given a dielectric
Given a capacitor with large plates (area $A$) separated by a dielectric with relative permittivity $\varepsilon_r$ and thickness $g$, I believe the Maxwell stress tensor states that the force on each ...
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Equivalent capacitance for a system of spherical capacitors
The question demands equivalent capacitance of two concentric metallic shells with larger and smaller radii. b and a respectively. The inner sphere is just left open(it's not earthed or anything), and ...
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Working of batteries and supply of charges through them when connected to capacitors
My doubt is not really related to capacitance but about the fundamentals of working of a battery.
A capacitor with certain capacitance is charged as shown in the figure.
Please note that battery is ...
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Growth of Current in an Inductor Connected Across a Battery [duplicate]
When baterry is connected across inductor with no resistance in circuit, won't the current flowing through it be zero, as inductor back emf will counteract the effect of potential difference due to ...
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Cannot catch a minus sign mistake when deriving the ODE for an LC circuit
It's probably a very basic question but I just cannot wrap my mind around it. I'll just try to derive the differential equation for an LC circuit:
According to the law of induction, in a solenoid we ...
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Using an imaginary conducting shell of infinite radius to calculate capacitance of a spherical conductor
This is a statement from Serway's Modern Physics which I don't understand. It tries to explain capaticance for a single conductor.
Imagine a single spherical charged conductor. The electric field ...
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Maximum voltage that a system of two capacitor withstands when connected in series [closed]
Question:
A capacitor of capacitance 1 micro faraday withstands the maximum voltage 6kV while a capacitor of 2 micro faraday withstands the maximum voltage 4kV. What maximum voltage will the system ...
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Surface charge density within a parallel plate capacitor on different voltages
I need a way to vary the surface charge density without changing the electric field. My idea is to use two large conducting parallel plates close to each other in vacuum enclosed in a grounded vessel (...
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Is the capacitance obtained using the RC circuit equation the correct value?
To find the dielectric constant of the dielectric according to frequency, an RC circuit was constructed and the capacitance was calculated using the RC circuit equation using the voltage applied to R, ...
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Electric field at any point in the region between two capacitors is proportional to the magnitude of charge on each conductor
This is a statement from Young and Freedman's University Physics Section 24.1 on Capacitors.
Suppose we have any two conductors with charges $-Q$ and $+Q$ on each charged with a battery. Then this ...
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How to solve the transient response of a general $RLC$ network?
There is a $RLC$ network $\{V_i\}$ with a complex impedance $Z_{ij}$ on each edge. all vertices have initial voltage $V_i$ and all edges have initial current $I_{ij}$. Now, is there a general way to ...
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Effect on a capacitor due to a dielectric
Why does the effect of a dielectric fully inserted between a parallel plate capacitor differ when the capacitor is connected to a battery source and when it is not?
When a charged capacitor is not ...
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Why does this RLC behavior differ from what equations predict?
In order to better understand RLC behavior under current sources, I constructed the simple circuit below and attempted to analyze it. However, my equations do not agree with simulation results.
The ...
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What are the limitations of Nodal Analysis?
Yea, that's the question basically. What are the limitations of Nodal Analysis?
Like, for example take the following case, we have to find out the net capacitance between A and B.
Now I want to solve ...
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Can a material have zero free charge density while having non-zero conductivity?
I solved this problem where a lossy dielectric (conductivity: non-zero constant, permittivity: non-zero constant) is placed between two plates. I found that the magnitude of $E$ is constant since divJ ...
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Is there simple harmonic motion when a dielectric longer than the capacitor is inserted into the capacitor? [duplicate]
I’m trying to understand the mechanics of a dielectric being inserted into a parallel-plate capacitor. Suppose I have a parallel-plate capacitor with plate separation d and a dielectric slab of length ...
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Current equation for a circuit containing 5 basic elements in series
Does a general equation (for current) exist for a circuit containing the five elements namely e(dc), e(ac), R, L (active/inactive), C (charged/uncharged) in series? If yes, can i derive from it the ...
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For a plane isolated capacitor with a dielectric slab partially introduced inside it, what's indpendent of the medium? $\mathbf E$ or $\mathbf D$?
Say we have an isolated capacitor with charge $Q$ and a dielectric slab, $\varepsilon_r$, partially introduced between the capacitor's plates, then, I'd say the displacement vector should be the same ...
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Charged plate between two different dielectrics
Imagine a charged plate, placed in between two DIFFERENT dielectrics of susceptibilities $\chi _1\:and\: \chi _2$ .
From Gauss's law, We can conclude that the sum of the magnitude of the electric ...
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Why does capacitance depend on medium?
Capacitance does not depend on charge or the potential difference due to it fundamentally being a constant which we have defined. I only have trouble understanding why does it then change if we change ...
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