Questions tagged [capacitance]

The ability of an object to store electric charge.

265 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
0
votes
0answers
17 views

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 ...
0
votes
0answers
18 views

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 ...
0
votes
1answer
30 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 ...
0
votes
1answer
41 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. $\...
0
votes
1answer
23 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 ...
0
votes
0answers
28 views

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 ...
0
votes
2answers
673 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 ...
0
votes
0answers
36 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:...
0
votes
3answers
59 views

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?
0
votes
0answers
27 views

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. ...
0
votes
0answers
147 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 ...
0
votes
1answer
50 views

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 ...
0
votes
1answer
108 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 ...
0
votes
1answer
124 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 ...
0
votes
0answers
217 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 ...
0
votes
0answers
81 views

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 ...
0
votes
0answers
84 views

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. (...
0
votes
1answer
93 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 ...
0
votes
0answers
30 views

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 ...
0
votes
0answers
87 views

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 $Q$, ...
0
votes
3answers
68 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 ...
0
votes
1answer
43 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 ...
0
votes
3answers
59 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 ...
0
votes
1answer
15 views

What is the reference potential when considering electric potential on a body in case of self capacitance?

I was taking a lecture on self capacitance and the word 'potential of the conductor' came up. Now, self capacitance is for isolated conductors. From what reference is this potential measured?
0
votes
1answer
104 views

Determining the relationship between plate separation distance and capacitance experimentally

On a lab I recently did, I measured the capacitance between aluminium foils over a range of distances. One of the subsequent questions was to determine the function that best describes the ...
0
votes
1answer
28 views

Charge stored in a capacitor with dielectric when relative permittivity varies

Suppose the relative permittivity of the dielectric in an uncharged capacitor of capacitance C varies with the voltage applied, e.g. k=xV where x has dimensions of V^-1 (After this capacitor is given ...
0
votes
1answer
71 views

Paradox on setting up charges on capacitors

Staring with facts, 1)For a current to flow there must be a closed loop. 2)For a capacitor to be charged there must be a potential difference across it, 3)And obviously a charge must be transferred ...
0
votes
1answer
43 views

Why does the charge required on each plate of a capacitor to maintain a certain voltage decrease with the distance between the plates?

The $Q$ charge and the voltage $V$ of a capacitor are linked by $$Q=C\times V$$ For a parallel plate capacitor $C\propto \frac{1}{d}$. This implies for a given voltage $V$ between the plates, the ...
0
votes
1answer
51 views

Why is the information of a time delay missing in formulae of voltage drop across elements when we emulate DC with an AC voltage supply?

In an AC circuit, the reactance of capacitive and inductive elements are determined by the frequency of the AC signal. When we try to emulate DC analysis by putting $\omega$ = 0 , the capacitive ...
0
votes
1answer
223 views

Cylindrical capacitor, why is the electric field radial between the two plates?

I'm trying to understand why if I consider a cylindrical capacitor whose height is $h$, the radii are $R_1$ (external) and $R_1$ (internal) and I put myself between the two plates I can say that the ...
0
votes
1answer
27 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 ...
0
votes
1answer
71 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 ...
0
votes
0answers
46 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 ...
0
votes
2answers
113 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}_{...
0
votes
1answer
153 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*}...
0
votes
0answers
98 views

Proper utilization of Ampere’s Law

I am tasked with finding the magnetic field due to a bus bar, which seems to have the exact same set up as Problem 7.62 in the fourth edition of Griffiths' textbook on Electrodynamics. To which I ...
0
votes
1answer
28 views

capacitor and electrostatic field

Is there any electrostatic field around the leads of a charged capacitor? Let's take just the negative one. If I take a piece of tissue and put close to that terminal it will attract or repel the ...
0
votes
0answers
89 views

Derive the formula for a capacitive voltage divider?

I've seen the derivation for a resistive voltage divider, Vout = Vin * R2/ (R1 + R2). For a capacitive divider, Vout is reported as Vout = Vin * C1/ (C1 + C2) - for example see https://en.wikipedia....
0
votes
3answers
52 views

About the capacitance of the capacitor

I would like to ask two questions here , 1. When a capacitor reaches to its maximum limit charge starts leaking and it ionises the air atoms . Well is it true ? As I'm not able to get an convincing ...
0
votes
0answers
280 views

capacitance of cube skeleton

A cube of 12 capacitors is very common problem. find capaciance accross edges we get 12c/7. But lets say we have 8 more capacitors involved now. that is we have capacitors at all sides of cube and ...
0
votes
1answer
80 views

Does an uncharged capacitor in a non uniform electric field have a voltage difference at its terminals?

If an uncharged capacitor was placed in a dc field would there be a voltage difference developed on its terminals related to the different locations of the two surfaces in the voltage field? Would the ...
0
votes
0answers
753 views

Capacitance of spherical capacitor when inner sphere is earthed

Consider the following derivation: (Source: http://www.ncert.nic.in/html/learning_basket/electricity/electricity/electrostatics/inner_sphere.htm) If a charge of $+Q$ coulombs is given to the outer ...
0
votes
0answers
74 views

rotating capacitor question

Imagine a simple setup. I have a copper disc and another copper element held close to the disc at one of it's sides, this element is stationary but the disc is rotating, the part between the disc and ...
0
votes
1answer
36 views

Error of capacitnace measurement using a multimeter

physics stack exchange Many multimeters have a setting for measuring capacitance. The multimeter I have has a precision of four significant figures, or in other words, it returns the value in the ...
0
votes
1answer
88 views

How do multi-meters measure capacitance?

Many multimeters have the ability to measure capacitance along with the ability to measure AC voltage, DC voltage, current, resistance ... The only equations I am aware of that determine capacitance ...
0
votes
0answers
27 views

Why didn't my Capactive Wireless Power Transfer work?

Today I had the delight of setting up a bipolar capactive wireless power transfer (CWPT) circuit for a school experiment. Disappointingly, it did not work. It was set up just like in the diagram ...
0
votes
1answer
73 views

Capacitor, stored energy versus reactive power

When an AC voltage U is put onto a loss less capacitor C the capacitor will require a certain reactive power Q (current 90 degress out of phase with the voltage): $Q=UI = \omega C U^2$ in VAr (Only ...
0
votes
1answer
39 views

Limit charge of electronic–hydraulic analogy of a compartment

I am doing a mathematical model of an hydraulic system and I am using an electronic-hydraulic analogy. Normally a compartment is simulated with a capacitor. But in my system I can apply a big ...
0
votes
1answer
378 views

Earthing a system of parallel plates

our sir has taught us that when in a system of conducting infinite plates kept parallel to each other, when any one of them is earthed, then the charges present on the free ends(i.e. the open sides of ...
0
votes
2answers
41 views

New charge of a capacitor

How does the load of a charged capacitor vary when placing a dielectric between the plates while keeping the capacitor connected to the battery? If we have a capacitor that we have charged to the ...