# Questions tagged [capacitance]

The ability of an object to store electric charge.

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### 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 ...
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### 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 ...
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### 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 ...
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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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### 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 ...
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### 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 ...
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### 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 ...
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. ...
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?
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### 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 ...
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### 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.
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### 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 ...
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### 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 ...
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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 ...
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 ...
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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 ...
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 ...
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### 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 ...