# Questions tagged [capacitance]

The ability of an object to store electric charge.

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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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### 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 ...
1 vote
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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, ...
1 vote
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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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### Why is the induced charge on the infinite plane expected to be $-q$?

3.2.2 page 123 of Griffiths E&M. Place a charge $q$ a distance of $d$ above an infinite grounding conducting plane. The total charge induced on the conducting plane is then $-q$. The last sentence ...
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### Capacitance coefficients of two enclosed spheres

I was reviewing G.B. Jeffery's work titled On a Form of the Solution of Laplace's Equation Suitable for Problems Relating to Two Spheres. To access the full text, you need to click "DOWNLOAD PDF&...
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### Capacitance of multiple overlapping metal layers

Consider a set of metal plates arranged in a similar fashion to the picture below: The capacitance between the layer labeled M5 and the layer labeled M4 can be calculated (ignoring fringe effects) as ...
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### Potential difference between two non-grounded equipotential plate

I am attempting to solve for the potential difference between two non-grounded equipotential plates using Poisson's PDE. The relevant Maxwell equation considered is $∇⋅E=\rho$, where $E$ represents ...
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### Maximum Impedance for LCR series circuit

Impedance of an LCR series circuit can be maximum when either Inductive Reactance or Capacitive Reactance is maximum at an instant of time. Max Capacitive Reactance is at minimum frequency, and max ...
Lets take for an example, a spherical capacitor with two dielectrics. The Electric Field will then be given by $$\frac{Q}{4\pi\varepsilon_0\varepsilon_r r^{2}}$$ We know that then the electric field ...