# Questions tagged [capacitance]

The ability of an object to store electric charge.

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### Current flowing in resistor after the switch is closed

I'm getting confused between the current flowing in $R_1$ and $R_2$ and the capacitor. Can someone elaborate on these questions? ε1 =2.5 V / ε2=4.0V C=22 microFarads R1 = R2 = 1.5 ohms Immediately ...
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### What is the electric field between two conducting parallel plate capacitors?

Actually i am confused about the difference b/w electric field due to a non-conducting charged plate and conducting charged plate. And what should we assume when it is not mentioned that which plate ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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: ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### $1 \text{m} \times 1 \text{m}$ 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 (...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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?
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### 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}{...
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### 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 $R$...
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### Dispacement 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...