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Questions tagged [capacitance]

The ability of an object to store electric charge.

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Possible to develop touch screen material in wrap form? [closed]

Does anyone know if it's possible to find/create the same material found in capacitive touch screen in bulk form? I'm looking to wrap a number of inanimate objects completely in touch screen capable ...
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2answers
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Charging and discharging a capacitor [closed]

So from what I understand, in the case for the charging capacitor, I understand the voltage across the capacitor as well as the charge can be given as the function of time: $$V(t)=\epsilon(1-e^{-t/RC}...
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RC circuit confusion [closed]

I was doing some RC problems in A levels, and in ine of thr problems it was about a circuit attached as a picture: My question is can someone clearly explain to me why when time goes to infinity , ...
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Calculating impedance and capacitance at resonance? [closed]

The impedance of an RLC series circuit is 8 ohms at resonance when f = 60hz but the impedance changes to 10 ohms when the frequency is increased to f = 80hz. Calculate the values of Capacitance, C and ...
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51 views

How is a capacitor implemented in Kirchoff's Loop Rule?

I'm real stumped here. I may be missing something, but I'm genuinely perplexed as to how one would add a capacitor to the list of elements being added to an equation through Kirchoff's Loop Rule (KVL)...
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1answer
20 views

Ratio of charges between capacitors in parallel and in series [closed]

Context: this is a multiple choice question, but no explanation is given Question: three capacitors of equal capacitance are connected in the following circuit. Determine the ratio of charge in ...
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Is the permittivity of a dielectric medium measured by application of radio frequency of 1 KHz and a resonant circuit of 1KHz are same?

I am working on a procedure in which I assess the dielectric constant of a medium by subjecting the dielectric medium to electromagnetic radiation of certain frequency (or the medium is subjected to a ...
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1answer
71 views

How to differentiate Capacitance (Italized C) and Coloumbs (regular C) on paper [closed]

I am doing a question on capacitance and coulombs. I got the answer correct, but I was wondering how a physicist, when doing the calculation on paper, would differentiate a C and C?
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Capacitors in Amplifiers [migrated]

I am reading about single stage CE Amplifiers and I don't understand how the capacitors work here. 1) Coupling Capacitors: "The coupling capacitor is used to isolates the d.c. of one stage from the ...
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1answer
29 views

How to compute the self-capacitance of a conductive shape?

(Depending on the answers given, this question might be better suited for Math.SE, but I don't think so.) I recently learnt about the notion of self-capacitance of a conductive shape, which now seems ...
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2answers
48 views

Question on capacitance

I am recently trying to learn electrics on my own but am a bit confused with regard to capacitance. By Gauss law, I understand that the electric field from a single parallel plate results in: $$ E = \...
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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 ...
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Partially Filled Capacitors

I know that, for partially filled capacitors, one treats the space between the capacitor plates as two or more capacitors either in series or parallel. However, I don't fully understand why the ...
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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 ...
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1answer
59 views

Why do we not have devices like inductors or capacitors to hold gravitational field? [closed]

I know that a capacitor can store electric field and an inductor can store magnetic field. So is there a way that gravitational field field can be stored in any such device. Also we do not have a law ...
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Does the capacitance depend on the distance?

I know that the Capacitance of a capacitor does not depend on the Voltage (because it is a measure for how much charge a capacitor can hold) and it largely depends on the Area i.e. it holds that : $...
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Van de graaff generator, Leyden jars and capacitance

How will the capacitance of a typical desktop van de graaff generator be affected when connected in series to a group of some 5-10 Leyden jars? I know that the capacitance is decreased in series ...
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2answers
34 views

The electric field between two plates of a capacitor

Suppose you a have a parallel plate capacitor connected to a battery of voltage $V$, and charge is starting to accumulate on the side of the capacitor connected to the positive end of the battery. ...
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1answer
42 views

Grounded parallel plate capacitor

What will be the charge distribution if a parallel plate capacitor, which is not connected to any battery, is given charge on one plate(say Q on the left plate) and is grounded on the outer side of ...
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1answer
35 views

Capacitor with a spring [closed]

The plates of capacitor are attached with non conducting spring of spring constant k. The initial separation between the plates is d and the spring is relaxed initially. Now the charges +Q and -Q is ...
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2answers
68 views

Capacitor demo explanation

I know that for a charged capacitor as one separates the plates further apart the voltage increases while the capacitance decreases. But surely as the plates are pulled further and further apart the ...
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1answer
58 views

Why don't transformers have capacitors?

I recently learnt about how resonance in an LC (inductor capacitor) circuit could increase the efficiency of the circuit, for application in something like Resonant Inductive Power Transfer. Excuse ...
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1answer
42 views

Energy loss in capacitor for slow charge transfer

From these questions: Energy loss in Capacitors What happens to half of the energy in a circuit with a capacitor? I come to the conclusion that energy loss in a capacitor is explained by the fact that ...
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57 views

Confusion in work done in moving charge to infinity from center of conductor

A point charge $q$ is at center of spherical conducting shell of inner radius $a$ and outer radius $b$. Find work done in moving charge to infinity. The answer (given in book) is: $$W = \frac{q^2}{8\...
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Why isn't there current in R2 when capacitor is not fully charged

If we consider the switch to be closed, why would there be no current in R2. My understanding is that, as the current flows it will split into two at the junction, thus having a current charging C and ...
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1answer
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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 ...
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Doubt on capacitors [closed]

Consider 4 capacitors connected in series Now a +2Q and +4Q charges are given simultaneously at marked locations in figure. Ignore the points A and B. My doubt is about the charge distribution that ...
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1answer
34 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 ...
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Touching single line of AC Power and charge oscillation in body

If a person touches a single line of AC(Only on the live line, and no where else. Say he/she is hanging on the power line using one hand) as shown in the attached image, Do the ions in his/her body ...
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1answer
38 views

Dielectrics in series, electric field strength

I am trying to apply a strong electric field to a porous material by applying a strong voltage across two conductive parallel plates that are sandwiching the material. Goal is to align dipoles in the ...
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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 ...
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Doubt regarding work done in separating capacitor plates [duplicate]

Suppose there is a parallel plate capacitor with distance between plates $d$ and it is charged to a potential difference $V$ and then charging battery is disconnected. Then the plates are further ...
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1answer
146 views

Question regarding why capacitance is a purely geometrical quantity

To show that the capacitance (of some capacitor), defined as $C \equiv Q/V$, depends solely on the geometry of the capacitor, we use that the electric field is proportional to the charge density, $\...
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Dielectrics in Capacitors [duplicate]

Is dielectric capable of storing charge? I mean if a dielectric is removed out of a charged capacitor will it still have charges stored into it??
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1answer
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Overdamped RLC circuit

I have a series RLC circuit with an equation: $$\frac{d^2I}{dt} + 2\alpha \frac{dI}{dt} + \omega_0^2 I = 0$$ (No outside sources affecting the circuit, only some $I_0$ was in the circuit at the ...
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54 views

Where does all the voltage go?

My understanding of this circuit is that the capacitor must 'use up' all the voltage across the terminals of the battery. If you double the distance between the plates, I would assume the voltage ...
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1answer
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Capacitive circuit

I was studying in one of my books that in a capacitive circuit in steady state with battery remaining connected ,if any external agent goes on separating the plates of the capacitor very slowly then ...
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4answers
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Why is the electric field between two parallel plates uniform? [duplicate]

According to sources online (eg HyperPhysics) the electric field strength around a point charge is $$E=k\frac{Q}{r^2}$$ This must means that the further you get away, the electric field should ...
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Change in electric capacitance and its factors

I've got some confusions regarding electric capacitance and I hope that you can help me see the picture more clear. Say that we have a capacitor with charge $Q$ and it's connected to a battery that ...
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3answers
44 views

Zero capacitances vs. infinite capacitances

Imagine a rc circuit with a capacitor with movable plates that have changeable area connected to a cell of voltage $V$ what if i pushed the plates towards each other till they touched? will this part ...
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1answer
60 views

Poynting's vector and its application to circuits

If I had a circuit as shown in the figure with the battery and the capacitor being covered completely, save for a passage for the conducting wire, by a hypothetical material that doesn't allow ...
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2answers
64 views

Capacitor asymmetrically charged

Can a capacitor be asymmetrically charged? I mean, not to have equal and opposite charges on each plate, -Q and +Q, but two different charges of any sign, say, q1 and q2. I ask firstly if it's ...
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3answers
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Charging a parallel plate capacitor if a dielectric is already present inside

A parallele plate capacitor is placed in a dielectric liquid such that one of the plates is inside the liquid and the other is outside. Then the plates are connected to a battery which supplies the ...
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2answers
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Capacitors in Series, which uses the most voltage?

AP Physics teacher here, preparing to teach my students about capacitors. We have some basic breadboards, capacitors, battery packs, and DC power supplies. My plan was to have them put three different ...
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Partial capacitances of a system of conductors - conductor acting as a shield

I have a small question about the following problem. The figure represents the cross-section of a three-conductor system comprising a communications coaxial cable of length l running parallel to a ...
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4answers
48 views

Is there a physical explanation for why increasing a capacitor's capacitance and the circuit's resistance decrease the capacitor's rate of discharge?

The voltage across a capacitor as a function of time is given by: V=Vi(e-t/RC) Therefore, increasing the resistance and capacitance increases the time it takes for the initial voltage to drop to e.g....
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1answer
26 views

Energy developed during change of capacitance

Considering a parallel plate capacitor connected to a battery. If plates are pulled apart heat is not produced. But the battery is absorbing energy as it gets charged. So is heat is absorbed. If ues ...
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1answer
52 views

Dual finite parallel disk capacitor; estimating mathematically that the potential or field or distribution is nearly uniform from first principles

Working through Purcell. In particular, doing my best to put everything on a firm footing, mathematically, so that I can understand it. But, I have struggled all week in establishing from first ...
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2answers
93 views

Electric Field between two parallel plans of opposite charge density

So considering two infinite parallel plans of opposite charge density let's say +σ for the left plan and -σ for the right plan Why is the electric field calculated this way : $$ E = σ/2εo + σ/2εo ...
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Capacitors phenomena

I wanted to ask one simple question: when there is a uncharged capacitor directly connected to a battery with any resistance in between, does current flow in the circuit, or does it only flow until ...