Questions tagged [capacitance]

The ability of an object to store electric charge.

Filter by
Sorted by
Tagged with
0
votes
0answers
29 views

How to calculate the electric field strength in between asymmetrical capacitors?

For a school project I am trying to calculate the thrust to power ratio of the electroaerodynamic drive aircraft invented by MIT. See this article on the MIT News web site for details. I need to know ...
0
votes
1answer
53 views

The self inductance of the motor of an electric fan is 10 H. In order to impart maximum powr of 50 Hz, it should be connected to a capacitance of [closed]

how can i solve this (*)The self inductance of the motor of an electric fan is 10 H. In order to impart maximum powr of 50 Hz, it should be connected to a capacitance of what is the concept behind ...
14
votes
10answers
4k views

Why does a capacitor act as a frequency filter?

What is it about a capacitor which allows it to filter frequencies? I understand the construction of a high-pass RC filter, and the mathematics behind it, but I'm struggling to find an explanation of ...
0
votes
1answer
31 views

How to calculate capacitance when inductance in known? [closed]

Below is the diagram (sorry for bad accuracy) that shows how current changes with time in LC circuit. On X-axis we have time measured in milliseconds (ms) and on Y-axis current measured in ...
0
votes
1answer
34 views

When a capacitor discharges in a simple RC circuit, is it treated as an active component?

While deriving expression for the voltage across capacitor in a discharging RC circuit, I stumbled across whether I should treat the capacitor as an active or a passive component(To properly apply the ...
1
vote
0answers
18 views

Need help understanding a statement about energy in capacitors

The electric potential energy stored in a charged capacitor is just equal to the amount of work required to charge it—that is, to separate opposite charges and place them on ...
1
vote
1answer
90 views

Full capacitance matrix symmetry property - how to derive it?

In this excellent article, the author, in sec. 1.4 describes the full capacitance matrix properties. He writes: The capacitance matrix is symmetric: $C_{ij} = C_{ji}$. This is related to the fact ...
0
votes
1answer
175 views

Equivalent Resistance Across Capacitor in RC Circuits

I need to find the equivalent resistance of the circuit here in order to find time constant. I know that I should replace current source with open circuit, then we have this: That 1k Ohm confuses me. ...
3
votes
2answers
412 views

Is the energy supplied to a capacitor by a battery the same as the energy stored by a capacitor?

If we have three capacitors in series, would the energy supplied to the system be the same as the energy that is contained in the equivalent capacitance of these three capacitors?
1
vote
1answer
31 views

Discharging of a capacitor

Consider a charged capacitor with its positive plate holding charge Q. Now I join the capacitor to an circuit with resistance R . So the capacitor starts to discharge. Small charge $q$ flows out of ...
0
votes
2answers
93 views

Why is the electric potential across a capacitor zero after a long time?

I was just exposed to this concept in class, that the electric potential across a capacitor is zero after a long period of time, but it was never explained why. This is for an RC circuit.
0
votes
0answers
20 views

Charge redistribution in term of Force

Suppose two spherical conductors each with a different radius. Initially, they are charged independently up to charge $Q_1$ and $Q_2$. Now let's that they are connected through a wire. Then the charge ...
1
vote
3answers
59 views

Why capacitance is constant? [duplicate]

I am new to the field of electrodynamics and I recently came across the definition of capacitance as $$C = \frac{Q}{V}$$ It is said that capacitance is constant, which implies that total charge of the ...
0
votes
0answers
45 views

Where does half of the work done in charging a capacitor is dissipated? [duplicate]

The energy stored in a charged capacitor of capacitance $C$ with $V$ voltage across it is: $$U= \frac 12 CV^2$$ Whereas the work done in charging the capacitor is: $$W= CV^2$$ This means that $(1/2)CV^...
0
votes
1answer
31 views

Charge densities when placing a conductor or a dielectric material inside a capacitor

Assume there are two conducting infinite plates. They make up a capacitor - one plate has a charge density of $\sigma$ and the other has a charge density of $-\sigma$. Assume the charges on them are ...
3
votes
2answers
68 views

In LC circuit, the EM waves specifically originate from where?

In LC circuit, we know that there will be charge oscillations, so emw will be produced. I just want to know emw will originate from where? Will it originate from within the capacitor? Or will it ...
1
vote
1answer
33 views

Working of Capacitive Accelerometer

I've been studying about capacitive accelerometers, and basically how they work is by detecting the change in capacitance or as a result of change in the distance between the conductive plates, small ...
0
votes
2answers
98 views

Why does force between plate capacitors not change when dielectric is inserted between them?

I was told in my physics class that the force does not change between the two plates but wouldnt the electric field not change between them bc it gets divided by the dielectric constant?Hence the ...
2
votes
4answers
118 views

How to convince myself that capacitance cannot be a function of voltage?

My textbook states that: ...The capacitance $C$ depends only on the geometrical configuration (shape, size, separation)of the system of two conductors. [As we shall see, later, it also depends on the ...
0
votes
2answers
280 views

Charge as a function of time in an RC circuit

In my professors notes, there is a function representing charge in terms of time, however there is absolutely no explanation to why this function holds true. It seems like he skipped the whole part on ...
1
vote
2answers
88 views

Electric potential and increased capacitance

I could really do with some insight into how the capacitance of a conductor increases when you bring another oppositely charged or earthed conductor near it. The explanation in my book is as follows: ...
0
votes
3answers
184 views

Will the free charge density on a disconnected capacitor plate change if I insert a dielectric?

We have a disconnected capacitor having charge density $\sigma_{1}$ on its positive plate. Now we fill it with a dielectric as shown. Will the free charge density( the mobile charges on the ...
0
votes
0answers
35 views

Physical resistor and capacitor structure and boundary conditions

From this figure, this structure is composed of a cylindrical resistor and capacitor. I am tasked with finding the resistance and capacitance of the top and bottom components. The problem I am working ...
0
votes
1answer
47 views

How does the charge accumulate inside a parallel plate capacitor?

I couldn't properly understand, how is it so that if I have a parallel plate capacitor, in which one plate has $+Q$ charge and another has $-Q$ charge then all the charge on the first plate will ...
0
votes
1answer
96 views

Intuitive explanation for why voltage decreases as distance between charges decreases?

A uniform electric field can be set up as shown: The force for a given charge will be constant anywhere in this field. However, as the distance from the charge to the oppositely charged plate ...
0
votes
2answers
125 views

Why does the capacitor charge through a resistor?

I was working on a question where there was a circuit and the switch was open, there was one capacitor and one resistor. It said: immediately after the switch is closed, what is the current in the ...
0
votes
2answers
57 views

Will energy in an LC circuit become 0 if its is disconnected when the capacitor is fully discharged?

In a recent test I had a question in which there was an LC circuit with an inductor a capacitor and a switch. According to the answer key If switch is opened when capacitor is fully charged energy of ...
0
votes
1answer
66 views

Time Constant of a Capacitor in DC

I've just started studying Physics and I'm not sure how you're supposed to calculate the time constant of a capacitor when a direct current is applied. DC means that frequency equals = so the ...
2
votes
2answers
77 views

Hamiltonian of a quantum circuit including a diode?

The LC circuit has a Hamiltonian: $$\hat{H}={E_L\over2} \hat{\varphi}^2 + 4E_C \hat{n}^2$$ where $\hat{\varphi}$ is the magnetic flux and $\hat{n}$ is the number of charge. What is the Hamiltonian ...
0
votes
0answers
38 views

$1 \text{m} \times 1 \text{m}$ parallel plate capacitor at $300 \text{ kV}$

I have a parallel plate capacitor 1 m x 1 m that is to be fully charged to 300 kV. The distance between the metal plates is 3 mm; the inner surface of one plate is to be coated with 1 mm ceramic (...
1
vote
3answers
96 views

Why are the capacitors in this circuit in parallel but not in series?

In the circuit, the capacitors are said to be connected in parallel. Why is that so? Edit: The switch will be closed and C2 is fully charged by C1 and no more current will flow between C1 and C2. The ...
0
votes
1answer
156 views

Capacitors and how electrons flow given the electric field direction

My question is given that a capacitor creates a two charged sides, by the electrons jumping from one plate to another thereby making one having an excess of electrons making it negative and the other ...
2
votes
1answer
54 views

Charge on the plate of the capacitor

I was reading parallel plate capacitors in my book today and there I saw that the battery provides +Q charge to positive plate and -Q charge to negative plate? But we know that only electrons can flow ...
0
votes
0answers
16 views

How to solve circuit in static electricty? [duplicate]

I just found this question, but I don't know how to solve it. The question has a answer, but still it don't give me the formula. the answer for numeber 1 is 0,0 a for number 2 is 40 for number 3 is ...
1
vote
1answer
64 views

Maximum charge of a separate capacitor plate

Suppose we have an initially charged parallel plate capacitor, then we separate the plates so each plate has a positive and negative charge (I did an experiment, the plates hold the charge), I think ...
0
votes
4answers
95 views

Experiment to show that current leads voltage by 90° in capacitor

I understand that current leads voltage by 90° in capacitor. How does one show that it is true by an experiment?
0
votes
3answers
157 views

Why changing the distance between two parallel plates capacitor will affect its charge?

I have a question that is bothering me, Lets assume that I have a parallel plates capacitor with distance $d$ between them. Now connect it to DC voltage source $V$. according to equation $$V=\frac{Q}{...
0
votes
1answer
51 views

Can it be the some energy will remain after long time? Capacitors and resistors [closed]

My question is pretty simple, but I'll have to describe the problem in order to ask it: We have a an RC circuit as we can see in the picture. The given details are: the resistance of the resistor $ R $...
0
votes
0answers
28 views

Displacement current value through dielectric

Will the displacement current be multiplied by K when a dielectric is placed between the plates of a capacitor? Will its value then be K times the value without dielectric. Will it be still equal to ...
0
votes
0answers
50 views

Why is the worst case input/output impedance of an $RC$ filter $R$?

I'm going through the Art of Electronics in my spare time, and I ran across a problem I've been scratching my head about for a few days. The book states that in the worst case for any $RC$ filter, the ...
0
votes
1answer
188 views

How exactly does a (capacitive) humidity sensor work?

How exactly does a humidity sensor work? For example, how can it differentiate between a relative humidity of 30 % and 35 %? I know how a capacitance works but for me that principle is way too high ...
0
votes
2answers
117 views

What is the capacitance of a spoon?

Has anyone measured it? I can't seem to find anything online for "spoon capacitance"; what's the expected (self-)capacitance on the typical household utility metal spoon? The spoon heads ...
0
votes
1answer
52 views

Heat produced by resistor in a circuit with charged capacitor and no battery [closed]

C2 has a charge of 8C and 4F capacitance. C3 has no charge and 2F capacitance. S2 is then closed for a long time. What is the total Joule heat generated in resistor R2? The answer is 8J/3 but I'm not ...
0
votes
1answer
76 views

Why doesnt a capacitor discharge when you ground one end?

I have grounded one end of my capacitor after charging it but the voltage drops at a steady pace not as if it has lost charge. Is this because the opposing charges on the opposite plate are keeping ...
0
votes
1answer
162 views

What does electrostatic energy stored in a region mean?

Recently my teacher taught me about Energy density(Energy per unit volume) and told us the formula for the same. This was explained by taking "Energy" as Energy of a parallel plate Capacitor ...
0
votes
1answer
69 views

Kirchhoff's voltage law for an ideal circuit containing only a capacitor

Let's say I have an ideal open circuit (i.e. there's no resistance in the conductors) containing only a charged capacitor and then I close it. Now, the charge on one end of the capacitor will move to ...
1
vote
1answer
92 views

Kirchhoff's Voltage Law does not hold for a free source RC circuit?

Say I have a simple free source RC as depicted in the image below. The capacitor initially has a charge of Q on its positive plate and at time t=0 the switch is close. I use the mesh current as shown ...
0
votes
1answer
42 views

Does the dielectric constant changes as the voltage is applied in every dielectric material?

As the voltage is applied at both sides of the dielectric material(ex. front surface +5V and rear surface 0V), the energy is stored in the material, right? I heard it's because the dielectric ...
1
vote
1answer
38 views

New interpretation for Heat in Resistanceless Capacitive Circuits

I have been studying RC circuits and noticed that even in a resistanceless circuit, when a capacitor is charged by a constant potential difference source, there is considerable heat generation, equal ...
1
vote
2answers
64 views

A theoretical question about matter/antimatter and capacitors

Let's assume that the experiment is done in a vacuum and there's a circuit as in the attachment. The values of voltage/resistance/capacitance are insignificant. Assume that the right terminals of ...

1
3 4
5
6 7
32