Questions tagged [capacitance]

The ability of an object to store electric charge.

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Resonance frequency with metal

I've made an experiment with resonance frequency of a LC circuit. One part was to place a metal (I think iron) in the middle of the induktivity of LC circuit. I measured a higher resonance frequncy as ...
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30 views

Change in distribution of charge on plates of capacitor on earthing one plate

If we consider the following situation: Now the capacitors are already charged so the potential difference between the plates is well defined but the absolute potential isn't. So what will happen if ...
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Liquid rising in a capacitor

Consider a parallel plate capacitor is placed in such a way that the plates are horizontal and the lower plate is dipped in liquid which has a dielectric constant k the plates are connected to battery....
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19 views

Circuit representation of internal capacitor resistance

In the circuit representation of a capacitor, why is the internal resistance of the capacitor, caused by the dielectric medium between its plates, taken to be parallel to it?
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What is the time constant of RLC circuits

I am trying to understand how to analyze and understand the $RLC$ circuit. I know that in $RL$ and $RC$ circuits there is time constant $\tau$ wich determine how long it will take to $I_{(t)}$ decress ...
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16 views

Magnetic field and permeability of a capacitor

As shown in this document, the magnetic field of a parallel plate capacitor with a permeability equal to that of free space is shown with equation (18). If a capacitor has a permeability higher than ...
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1answer
37 views

RLC - CLR - RCL Transfer function

I have problem because I don’t understand the difference between CLR RLC and LCR, they are the same no ? They have the same composant just placed in different ways, I did already found the Transfer ...
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2answers
87 views

Heat dissipated on switching the wire?

$C$ and $C_0$ are the capacitance of the capacitors. The wire marked with an arrowhead is to be switched from point 1 to 2. Resistance of wires is very very less (~0). Leaking of charge does not occur....
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32 views

What is the charge stored by the capacitor?

I learnt that for an uncharged capacitor of capacitance $C$ connected with battery voltage $V$, the energy stored by capacitor is equal to $\frac{1}{2}CV^2$. But in this example for the capacitor ...
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26 views

Product of Capacitance and inductance in parallel plates

I was solving this problem: I was asked to find the capacitance per unit length, which I did (in cgs units) $$C=\frac{w}{4\pi h}$$ and to find the inductance per unit length $$L=\frac{4\pi h}{c^{2}...
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33 views

Can one capacitor charge another connected by a single lead only?

My instructor presented the following problem on capacitors: Plates 1, 2, 3, and ...
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42 views

For which reason do we say that the charge surface density is rougly constant (uniform distribution) on a capacitor's plates?

Consider for instance a parallel plate, a spherical or a cylindrical capacitor. Usually we analyze it by considering the surface charge density on each plate uniform, i.e. constant along the plate. ...
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26 views

Can a capacitor have zero potential when connected with another capacitor

I saw a question where it says that two capacitors of different capacitance $C_1$ and $C_2$. $C_1$ is charged with potential of $200\mathrm{V}$ and $C_2$ is charged with potential of $120\mathrm{V}$. ...
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Calculating energy exerted on individual atoms/molecules in a dielectric

If you have a dielectric material with a given dielectric constant (say one in a parallel plate capacitor for simplicity) that is polarized by a given electric field, can you calculate the effective ...
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17 views

Equivalent lumped element model of an inhomogenous distributed transmission line

Good day, I'm interested in an equivalent-circuit type problem that might be closely related to this question and its answer. What I am considering is sketched below: Essentially what I meant to ...
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24 views

Dielectric material and capacitor

First, If something is unclear because of my English, let me know. Assume I have a two-board capacitor connected to a power supply which delievers constant voltage value,and I am willing to fill it ...
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32 views

If a capacitor plate is equipotential then how come it has different potentials on the inner and outer plate during the charging phase?

I have a very fundamental doubt: Consider a capacitor with plates name $X$ and $Y$, Since the plates of capacitor happen to be conductors, they are going to have equal potential at all points. Now ...
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Point charge between two Concentric Conducting Shells in a RC Circuit

Suppose we have placed a point charge Q at distance, 'd' between two concentric, neutral conducting shells of radii 'a' and 'b'. We can connect the two shells through a resistor and switch. I wanted ...
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16 views

Self-capacitance of electrodes in capacitors

I thought about a way in which we could increase self-capacitance of electrodes in a dielectric capacitors. Is it possible to create an internal electric field in each electrode which would have an ...
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72 views

Discharge only one plate of capacitor?

what would happen if : Charge a parallel plate capacitor with battery Then disconnect the battery And finally, connect the positively charged plate to battery ground (similar to the induction-charged ...
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1answer
38 views

Effective time constant of an RC circuit

I have read in some books that to determine the equivalent time constant of charging of a capacitor in any RC circuit containing either only one capacitor and any number of resistors arranged in any ...
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86 views

In a fixed voltage case, why does inserting a dielectric increase the energy by a factor of $K$?

When inserting a dielectric, the electric field will do a positive work, and it will lose energy to attract the dielectric. by comparison, when dielectric is inserted in a charge-constant case, this ...
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1answer
32 views

Inductor real charcaterstics when connected to an ac supply

When we connect a dc source to an inductor we always use a resistor there so after solving that RL D.C. circuit we find an exponential function (e to the power R/L based) But when we are considering A....
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23 views

Resonant and non-resonant terms in $RLC$ cirquit

I have tried to solve a differentials equations of a RLC circuit. In the the solution I have terms proportional to $e^{iw_0t}$ and $e^{-iw_0t}$, where $w_0= \sqrt{1/LC}$. The author proposes in the ...
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What material should I use for the plates of my homemade mica capacitors?

I recently acquired some mica as i want to build my own high voltage (50 kV if possible) capacitors. The problem I am encountering right now is that the surface of such a crystal isn't perfectly flat ...
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Large Equivalent series resistance for polarized capacitor

Consider a standard RC circuit with a $100 k\Omega$ resistor and a capacitor. Here's some issue encountered during the lab. When using specifically a polarized capacitor($20 \mu F$), in addition of ...
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Ferroelectric energy storage

Let say we have a ferroelectric capacitor which is capable to store 1 joule of energy. Then we remove charged plates and remain only fully polarized ferroelectric. Are there some ferroelectrics which ...
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1answer
28 views

Circuit breaker and capacitance

I have a problem with knowing witch capacitor to use in a circuit because I am working on installing main circuit breaker where it is needed for 220 Volt AC current to be turned in to a lower current ...
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1answer
32 views

$E$-field between dielectric and plate in parallel plate capacitor and Feynman's claim

Feynman says about $E_{0}$ below Note that the field $E_{0}$ between the metal plate and the surface of the dielectric is higher than the field $E$; it corresponds to $\sigma _{free}$ alone. $\...
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1answer
18 views

Time constant relevance and definition for an RC or any 1st order RC/RL or a 2nd order RLC circuit

Can someone clearly explain what it is meant by the time constant of an RC circuit. Because from what I have been told it is the time taken to charge the capacitor. However, when I search on google it ...
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Is there such a capacitive transformer?

I've been thinking if it's possible to have voltage transforming effect based on capacitor. Will it work if a ferrite core, those "I" and "E" plates, be placed, and istolated throught mica, between 2 ...
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215 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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27 views

Cylindrical/Spherical Capacitor derivation sign issues

In deriving the capacitance for a cylindrical and spherical capacitors, I keep obtaining the incorrect sign on V. I completely understand the problem besides one step. First we start with Gauss' law:...
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Types of circuit

In this image one plate of C1 is at potential of 100v and one plate of C3 is earthened. Which type of circuit is this? If it's open, why would the charge flow?
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Enquries about capacitance of parallel plates with a dielectric slab between it while being connected to a constant voltage source

As the title suggests, it is a question about parallel capacitors. I believe that it would be hard to understand what my question is if I am going to directly type it out. Please take a look at below. ...
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95 views

Why is electric field between concentric spherical conductors NOT zero?

In studying electrostatics i learned that the electric field inside a conductor with no charge on the inside is always zero. I understand why this is, and i understand that no stable configuration of ...
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Lagrangian of $LC$ oscillator: where is encoded the fact that ($U$, $Q$) and ($U$,$\dot{I}$) are proportional?

Consider an L.C circuit with no driving. The equation of motion is, with $\omega_0=\frac{1}{\sqrt{LC}}$ $$ \ddot{Q}+\frac{1}{\omega_0^2} Q = 0$$ We can show that the following Lagrangian correctly ...
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Is capacitance of conductor an Intensive property?

Capacitance is the ability of a conductor to store a charge. Capacitance is always told to be similar to water tank. Capacitance can't be changed by presence of other charges. But at the same time ...
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62 views

How the total energy of a LC oscillator remains unchanged while placing a coil near the inductor of the LC oscillator?

If the capacitor is initially charged with Q charge and then conected to a inuctor then discharging takes place and the energy stored in electric field gets converted into the energy stored in ...
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1answer
104 views

Few conceptual doubts based on the effective capacitance of two metallic spheres joined by a metallic wire

The following problem is from Concepts of Physics by Dr. H.C.Verma, from the chapter "Capacitors", page 166, question 12: Problem: Two conducting spheres of radii $R_1$ and $R_2$ are kept ...
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158 views

Fringe fields do not explain the origin of the force pushing dielectric slab inside a capacitor?

In the problem of a dielectric slab being inserted between the plates of a parallel plate capacitor, it is usually argued that the origin of the inward force acting on the slab is the fringing ...
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4answers
102 views

Work done by battery on a capacitor

Work done by battery on a capacitor is QV/2, where V is the final potential across the capacitor plates an Q is the charge. I know that the Q charge which gets stored on the capacitor comes from the ...
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What should be Lecture flow while studying electrostatics, capacitor and current electricity?

Sometimes while studying electric field and charges I get some new terms, and while studying electric potential I get confused how the potential works. And then while studying current electricity, I ...
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Dielectric Slab: Force due to fringing field

A parallel plate capacitor whose plates are maintained at a constant potential difference has a partially inserted dielectric slab. The force on the dielectric slab is given in most of the books. (...
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1answer
65 views

Does insulating sphere have a capacitance?

A conducting sphere with radius $r$ has capacitance $C=4\pi \epsilon_0 r$. This can be derived as follows: $$ C=\frac{Q}{V}=\frac{Q}{\frac{Q}{4\pi \epsilon_0 r}}. $$ Now I am wondering if this ...
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Is the EM wave around a capacitor a standing wave or a traveling wave when AC current flows into that capacitor?

Please, check the following pdf file. http://web.mit.edu/8.02t/www/802TEAL3D/visualizations/coursenotes/modules/guide13.pdf It looks like that the two conductors of Fig.13.4.6 is just capacitor ...
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Are those two capacitors in parallel?

I'm trying to analyze the following situation: we have a parallel plate capacitor where the plates are both squares with side length $l$ and on the positively charged plate we have a charge $Q$, ...
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3answers
46 views

Is electric potential of the grounded conductor of a capacitor always zero?

In a spherical capacitor, the net electric potential on the outer grounded conductor due to the positive charge on the inner conductor and the negative charge on the outer conductor is always zero. Is ...
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1answer
36 views

Voltage between parallel capacitor plates

We know that $C=q/U$. We know that the voltage is the potential difference between the plates. If we have a capacitor on which we apply voltage, the one plate charges up and induces the other one with ...
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3answers
54 views

Understanding simple LC circuits

I'm trying understand the physics of simple inductor-capacitor circuits such that there is just an inductor L and a cacpacitor C and a switch. Imagine first that the capacitor is fully charged and ...