The ability of an object to store electric charge.

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Where extra stored energy of Capacitor go ? [duplicate]

Suppose We have a capacitor with capacitance $\ C $ and charge $\ Q $ . So total stored energy is $$ E=\frac{Q^2}{2C} $$ Now if I connect a capacitor with same capacitance parallel with it then ...
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1answer
60 views

How does differing surface resistance in a parallel plate capacitor effect the field strength?

I have been trying to find out how using different conductive materials for each parallel plate for a parallel plate capacitor will effect the field strength. Meaning if one of the parallel plates ...
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2answers
124 views

Battery charging a Capacitor

Ok I know there is a similar question already on here, but mine takes it just a step further. What I would really love to know is exactly how much energy is being transferred from a battery into a ...
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4answers
262 views

How to calculate the work of the electrostatic forces in a parallel-plate capacitor?

The expression of the energy stored in a parallel-plate capacitor is: $$U = \frac{e_0\cdot A \cdot V^2}{2d}$$ with $e_0$ the vacuum permittivity, $A$ the surface of the capacitor, $V$ the applied ...
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0answers
70 views

Resistor and conductor and inductor

What I am gonna to have if: -an inductor is in parallel with a capacitor and all that group is in parallel with a resistor. I know that a capacitor in parallel with an inductor is: $$\frac{1}{Z}=\...
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2answers
46 views

Time constant for this RC circuit

Well one problem boiled down to the following RC ciruit- $C_1$ was initially charged with $q_o$ and I thought after closing switch connecting $C_1$ and $C_2$ the maximum current discharging will be $...
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0answers
22 views

What size aluminum foil capacitor would power an LED?

Inspired by this video where a $9 \mu F$ capacitor is made from aluminum foil, if I had students put this together in a classroom, one question I would have is what would it take to have this power an ...
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1answer
50 views

Breakdown field in a capacitor

Let us say that air breaks down at a field strength of $E_b$. For a capacitor to arc, does there need to be a path between the two conductors such that for every point on that path the electric field ...
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78 views

Capacitor and Pith Ball experiment

Suppose I first charge a capacitor so that one plate is positively charged and another negatively. Now I remove the charging source and ground only one of the terminals say negative terminal, will ...
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1answer
763 views

How does a bulb light up when it's connected in a circuit with an uncharged capacitor and a cell?

Since there is a capacitor, isn't it an incomplete circuit? How does the current flow across the dielectric medium? If a bulb was connected to a cell alone and if there was a break in the wires of the ...
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0answers
29 views

Comparison of capacitances

The figure shows two arbitarily shaped surfaces S1 and S2.S1 is a thin metal foil, which has been slowly beaten to form the surface S2 without any loss of charge.. S2 lies completely within or on the ...
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1answer
105 views

Electric field between capacitors [closed]

A parallel-plate capacitor consists of two parallel, conducting plates of area $A$, separated by a distance $d$. Each carries a charge of magnitude $Q$; positive on one, negative on the other. Using ...
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19 views

Why the magnitude, $E$, of the field vector is different for every sets of (parallel) plates?

This is quoted my textbook. I wonder why we can't reproduce the same magnitude on a different set of plates, if we make them the same size, same charge, and having the same electric potential, and ...
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1answer
113 views

Transfer function of an RC circuit

I'm trying to reach the transfer function of an RC circuit which I am told is $$\frac {V_R} {V_\text{in}} = \frac{R}{\sqrt{(R^2 + \frac {1}{\omega^2 C^2})}} \cos(\omega t - \theta) \, .$$ Is this ...
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2answers
323 views

How long does it take for a capacitor to be fully charged if voltage is decreased? [closed]

Above is the picture of the circuit pertaining to this question. The question asked for the time it will take for the capacitor to get fully charged when the switch is in position B? So i guess the ...
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1answer
61 views

Mutual capacitance upper limit

I am having trouble making an analog for mutual capacitance from mutual inductance. In circuits with magnetic coupling, there is an upper limit established on mutual inductance due to energy ...
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2answers
243 views

Current on both sides of a capacitor

When a capacitor is connected to a DC circuit, what ensures that the current on both sides of the capacitor is the same? When charges arrive at one end of the capacitor they stop moving; presumably ...
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2answers
542 views

Work done by battery and potential energy of a capacitor

I have a doubt about the work done by a battery and the potential energy of a capacitor? 1- Consider a circuit where the capacitors are connected to the terminals of a battery. Through calculations ...
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1answer
297 views

Grounding a capacitor

When one of the plates of an isolated capacitor is grounded, does the charge become zero on that plate or just the charge on the outer surface become zero?
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32 views

What is the capacity of this circuit? [duplicate]

I simply can't figure out what the capacity of this circuit is. I can do the math myself, I just need a hint how to create an equivalent circuit where it is obvious what is parallel and what is in ...
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1answer
123 views

How is the formula for the capacitance of a parallel plate capacitor derived?

I have seen in I.E. Irodov that if the permittivity is given as $\epsilon$ then we can find the capacitance as $$C = \frac{\epsilon A}{d}$$ but I wonder whether it is dimensionally correct or not and ...
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1answer
49 views

Coaxial waveguide - wave impedance

Determine the capacity $C$ per $m$, the inductance $L$ per m and the wave impedance $Z_0$ for a coaxial waveguide with inner radius $a$ and outer radius $b$. How large would $b$ have to be so ...
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1answer
196 views

Cylindrical capacitor in an electric circuit

I've come across a tricky question and would appreciate some hints or explanations as to why the given solution is the way it is. The question reads as follows: A coaxial cable consists of a wire ...
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2answers
170 views

Charge between parallel plates given voltage

When you connect a parallel-plates capacitor to a voltage source, why is it assumed that the plates will have equal but opposite charge? According to the formula, the voltage only fixes the charge ...
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1answer
379 views

Circuit with capacitor and two resistors - total current - charge - differential equation [closed]

Consider the circuit below consisting out of a capacitor C and two identical resistors R. For $t<0$ the switch is open and the capacitor is uncharged. At $t=0$ switch is shut and the circuit is ...
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81 views

Maximum current in LC Circuits

Two capacitors of capacitance $C$ and $3C$ are charged to potential difference $V_o$ and $2V_o$ respectively and connected to an inductor, all three in series. Now the switch S is closed. Find the ...
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1answer
392 views

Loss in energy while charging a capacitor

Suppose a capacitor having capacitance $C$ is being charged using a cell of emf $E$. By the time the capacitor is fully charged, the cell has supplied $QV$ energy while the potential energy of the ...
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1answer
575 views

Capacitance of three plates

I'm sorry if this has been asked before, but here it goes. Consider three parallel plane conducting plates (they can be infinite) and suppose the middle plate has some thickness $\delta$ and the other ...
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1answer
284 views

Why is this electric field due to one plate of a capacitor $\sigma / 2 \epsilon_0$ when the capacitor plates are finite?

We know that electric field due to an INFINTE large sheet is constant and at INFINTY the electric field is not zero. But say if I take a finite sheet of length l and width w. Then the electric field ...
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2answers
111 views

Please give your valuable opinion in this capacitor problem! [closed]

The plates of a parallel capacitor are given charges +4Q and -2QThe capacitor is then connected across an uncharged capacitor of same capacitance C. What is the final potential difference between ...
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1answer
2k views

Capacitance of spherical capacitor when earthed

The capacitance of a spherical capacitor is given by $$C=\frac{4\pi \varepsilon_{0}}{\left ( \frac{1}{a}-\frac{1}{b} \right )}$$ How can I find out the capacitance of the capacitor when The ...
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2answers
62 views

Why does electrical impedance have as many parameters as it has?

The impedance of a circuit is written: $$ Z(R,L,C,f) = R + j ( 2 \pi f L - \frac{1}{2 \pi f C} ). $$ What is the line of thinking that frequency, resistance, capacitance, and inductance are the only ...
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3answers
313 views

Capacitance of a single charged plate?

Lets say we have a single plate that has a charge of +Q on it. A plate with charge -Q is infinite distance away. Will the plate with +Q have a capacitance associated with it? Why or why not? I was ...
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3answers
54 views

Effect on capacitance when capacitor number increased [closed]

What happens to total charge and potential difference when number of capacitors increased in series and parallel combination? My question in text book is: Initially, a single capacitance $C_1$ is ...
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1answer
38 views

AC pass through capacitor

I am confused how AC pass through a capacitor? Can any one explain or have the vedio how AC pass through capacitor?
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3answers
127 views

Parallel-plate capacitor working voltage $V={Qd\over{\epsilon_0 A}}$ relationship with plates' distance

I don't understand why the working voltage of a capacitor increases with the plates' distance. Suppose we have 2 capacitors in series where $C_1=12,0\mu F$ and $C_2=4,0\mu F$. The voltage over both ...
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3answers
85 views

Does the equation CV = q break down when V is small or a wire is very long?

I'm trying to understand how the equation $CV=q$ relating the voltage difference and charge stored on a charged capacitor breaks down under extreme circumstances. In most problem statements that I'm ...
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1answer
49 views

What happens here in this capacitor?

What happens when we earth the circuit as shown below, why should it matter? because potential at a point is relative? So if the earlier potential was $V_p$ at that point, it becomes $0$, so every ...
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5answers
233 views

Convert kinetic energy of a bullet into electricity and store it in a super-capacitor [closed]

I was thinking about bulletproof materials, they have to be so thick and heavy because they try to hold all of the kinetic energy of a bullet and then dissipate it (right?) So what if you made a thin ...
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1answer
148 views

Capacitors and Voltage

Imagine if I have a capacitor, connected to a battery of $12 V$. After charging the capacitor, I increase the plate separation. Then my capacitance decreases, right? But charge should be ...
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2answers
178 views

Current in discharging capacitor through fixed resistor?

In the textbook I'm using for physics it says that the charge left on the plates of a capacitor after time $t$, that is discharging through a fixed resistor, is $Q=Q_0e^{-t/\tau}$ where $\tau=RC$ is ...
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3answers
345 views

Deriving ODE for voltage across capacitor-RC circuit [closed]

I need to derive an ODE for the voltage across the capacitor in a specific RC circuit. The circuit has 1 resistor, one input, one capacitor and a switch. So far I have $$\frac{dv}{dt} =\frac1CI(t),$$...
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0answers
140 views

Circumference measurement using a capacitive sensor

I have a question which I hope someone in here can help me answer. Background: I’m building a device where I intend to use a stretchable capacitive sensor to define the radius change of an object. ...
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0answers
74 views

What's an intuitive understanding of diffusion capacitance?

Diffusion capacitance often comes up in transistor design. It is one of the two main capacitances you see, the other being the depletion layer capacitance. The depletion layer capacitance (per unit ...
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2answers
169 views

Charging a capacitor using a capacitor?

I recently did an experiment using a fully charged capacitor (assumed) and charged a separate capacitor through fixed resistor. We measured the potential difference of the capacitor being charged. We ...
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1answer
3k views

Calculating half power frequency (frequency response)

I am having a doubt in calculating half power frequency for a given RLC AC circuit. I have attached images of two questions with their solutions. In the first question, the equation for $\cfrac{|V_2|}{...
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1answer
481 views

The definition of mutual capacitance

I am not sure I completely understand the definition of mutual capacitance. Let's say we have two conductors, $A$ and $B$, so that the following holds: Both conductors are isolated. $A$ is isolated ...
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1answer
185 views

Graph of energy stored in capacitor?

Question: In an experiment a capacitor is discharged through a constant current. Draw a graph of how the energy stored in the capacitor varies with time. The answer given is: But I seemed to get a ...
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1answer
63 views

When a capacitor finishes charging

When a capacitor is fully charged I usually hear the phrase "the potential difference across the capacitor opposes the battery potential difference, so no more charge flows". What does "the potential ...
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1answer
289 views

Charging a capacitor (terminals)

When a battery is connected to a conductor electrons are repelled from the end of the conductor connected to the negative terminal of the battery and flow to the end of the conductor connected to the ...