The ability of an object to store electric charge.

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Capacitor charge and current as a function of type question [on hold]

Two capacitors, one resistor and an ideal battery are connected through switches s1,s2 and s3 as shown in figure. Initially capacitor of capacitance 4C is charged, while other is uncharged. The upper ...
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38 views

Understanding parallel plate capacitors [on hold]

I need help with understanding this assignment. I originally though of using the equation of Eo*A/D = Q/ΔV but I don't know how to answer this without actual numbers to plug in besides the epsilon-not ...
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30 views

Help to solve a circuit with capacitor and resistor

Till now I'd never solved a circuit with resistor and capacitor. I'd seen the problem and tried to solve. But now I am in a doubt.The circuit was like that- My attempt-
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24 views

Determining initial voltage across a capacitor [on hold]

This one has got me stumped. I have a graph of voltage vs time and a corresponding power vs time graph. Taking the integral of the power vs time graph gives me the work done on the capacitor. Now the ...
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2answers
25 views

Potential across the plate of a capacitor

So I came across this question: Two capacitors are connected in series of given capacitance $5\ \mu\mathrm F$ and $10\ \mu\mathrm F$. The first plate of the $5\ \mu\mathrm F$ capacitor is given a ...
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34 views

Sign of induced EMF and other elements in AC circuit

I am having problems to determine the direction of the induced EMF in AC circuits. For example, we have an inductor of inductance $L$. The induced EMF is given by: $$ \epsilon = - L \frac{di}{dt} $$ ...
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2answers
49 views

How do two metal balls of radius $r$ kept at a large distance form a capacitor? [closed]

So this is something really new to me. I have learnt of plate capacitors, cylindrical capacitors, single spherical capacitors, etc. but that to, of finite distance between them. Also please explain if ...
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1answer
44 views

Problem with differential equation RLC circuit serie [closed]

I am trying solve the differential equation of RLC's circuit in serie, I have: $C=4\ F, L= 1\ H$, $R=5\ \Omega$, and $V_e=20\ V$. $1)$ first I got the equation, it is: $i''+5i'+\frac{1}{4}i=0$, what ...
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22 views

Displacement current in a capacitor

I recently learned about the concept of displacement current in a capacitor. I've understood the basics - mainly understood the reason why it was introduced. However, is it purely a mathematical ...
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37 views

Capacitance of two non parallel plates with two dielectric materials

There is one answered question about the two non parallel plate capacitance here. However, it only has one dielectric material. I am looking for a formulae of the same configuration, but with 2 ...
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0answers
27 views

Capacitor connected across two isolated sources [duplicate]

Lets say there are two isolated sources of positive charges $q_1$ and $q_2$ $(q_1>q_2)$ located sufficiently far apart. If the two are connected to the two plates of a capacitor, then what is the ...
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1answer
44 views

RC circuit discharging capacitor, trouble understanding

If we apply loop rule while charging the circuit we get: $$\varepsilon -iR-\frac{q}{C}=0$$ The way I understand, we follow trough the circuit just before the battery, as we move trough the circuit ...
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43 views

What is capacitance, in general?

In circuit analysis software capacitance can be measured between any two nodes of a circuit or of a multiterminal device. In practical terms we take $C_{ij}$, the capacitance between $i$ and $j$ as ...
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0answers
19 views

Is it possible to make a capacitor of required specifications using aluminium foil? [closed]

I wanted to make a FM radio transmitter but I was not able to get a capacitor with the exact rating of certain micro farad and pF. But I live in a poor country and I can not find them in the local ...
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1answer
42 views

E field of parallel plates with metal inside

I was asked to determine the electric field in the spaces between the copper bar and the plates. The voltage across the plates was 30 V, so naturally I’d use $E=\Delta V/d$ to determine the field. ...
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29 views

Circuit with three capacitors

A potential difference of V = 38.0 V is applied across a circuit with capacitances C1 = 4.1 nF, C2 = 4.7 nF, and C3= 2.3 nF, as shown in the figure. What is the magnitude and sign of q3l, the ...
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1answer
38 views

Closing a switch in series with a capacitor

Suppose we have the following circuit: Such that for $t<0$ the switch M was open. If we close the switch at $t=0$ what will the voltage on the capacitor, $V_C$, be at $t=0^+$? What about $\dot ...
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3answers
58 views

What would be the capacitance of an unequal charged capacitor?

I searched for this question but I cannot get satisfactory answer. Say if we have a parallel plate or cylindrical capacitor and if I supply unequal charge to it how could I find its Capacitance. We ...
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2answers
997 views

Are capacitors and inductors mirror images of each other?

I'm reading through my E&M textbook (Physics for Scientists and Engineers 3rd edition, Knight) and watching as many lectures on YouTube (Shankar, Pomerantz, Lewin, etc) to prepare for next ...
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37 views

What are the first couple terms of the Taylor series for the evolution of this network of capacitors and resistors?

note: This is a computational problem, and I only need approximate accuracy, so the overall goal is, for a given accuracy and $\Delta t$ to compute the state of the system at $t+\Delta t$ to within ...
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2answers
42 views

Parallel RLC circuit, how branching currents may each be larger than source current at resonance?

How can the branching currents individually be greater than the source current?
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1answer
60 views

In an RLC series circuit on resonance, how can the voltages over the capacitor and the inductor be larger than the source voltage?

Consider an RLC circuit in series, of the form If the source drives the circuit in AC at the resonance frequency $\omega =1/\sqrt{LC}$, the peak-to-peak voltages on the capacitor and the inductor, ...
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1answer
41 views

Power Dissipated by Resistor in AC Circuit [closed]

I'm having a problem with the following review question: Given the circuit: I am asked to find the power dissipated by R1 and C. I know that for C it is 0. For R1, I know I need to use Vrms ...
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0answers
9 views

Calculating pressure on a dielectric kept inside a capacitor

Firstly, the pressure is because of the opposing forces acting on both sides of the dielectric slab. On the left side of slab, the field due to the left plate is $\frac{\sigma}{2\epsilon_0}$ and ...
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2answers
25 views

smallest possible length of copper wire, where I can measure capacitance via multimeter [closed]

I am a new highschool physics instructor and I want to show to my students the basic concept inside the capacitors. i plan on showing them via simple 2 copper wires side by side each other, supplied ...
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1answer
52 views

Voltage and Energy in a capacitor [duplicate]

Well, my first question is related to the energy of the capacitor. Why does the energy of capacitor equals $E=\frac{1}{2}QV$ and not $E=QV$;in other words, why we multiplied it by $\frac{1}{2}$?? My ...
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1answer
28 views

Filling a charged capacitor with dielectric material

If there is a charged capacitor (capictance $C$) connected to a battery (of EMF $V$) and the space between the plates of the capacitor is filled with a dielectric material (dielectric constant is ...
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3answers
63 views

What is the potential difference between $a$ and $b$ in this basic circuit, when the switch is open? [closed]

My professor says the potential difference between $a$ and $b$ is the difference between the voltages on the top left capacitor and the bottom right capacitor. My friend and I however both think it's ...
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1answer
29 views

Why is the energy lost due to the internal resistance always equal to $(1/2)CV^{2}$ in a simple capacitor battery circuit? [duplicate]

Suppose we have simple circuit in which a battery of EMF $E$ is connected to a capacitor of capacitance $C$. Work done by battery $W_{b}=CV\times V$ and energy stored in capacitor ...
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0answers
12 views

Capacitative energy of a general concentric shape of short separation

Consider a surface $\partial \Omega$ whose enclosure describe a three-dimensional shape $\Omega$ of characteristic length $L$. On this surface resides an inhomogeneous surface charge density ...
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1answer
26 views

If iI have a capacitor connected to a battery can the negative charge be sent to an insulated object

If I have a capacitor permanently connected to a battery, that is lets say setting in a plastic bowl, and then run a wire from the negative of the battery to a non grounded object, say a metal can ...
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21 views

Physics Question related to capacitance and discharging. (very basic)? [closed]

A teacher wants to use a 0.05F capacitor and a 0–10mA ammeter to demonstrate capacitor discharge in a time of no more than 5 minutes. Suggest suitable values for the charging voltage and the ...
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23 views

Average distance between electrons on a parallel plate capacitor

I came across this question in an old exam paper and I am interested in the way it was marked. The 'correct' answer doesn't seem to be as correct as it could be. Calculate the average distance ...
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1answer
35 views

Capacitance question

A capacitors capacitance, C is equal to Q/V right? If Q was somehow cut in half, would the potential difference also be cut in half, since V is directly proportional to Q? And if so, Its C would be ...
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2answers
39 views

Battery and charge separation

In this question : What is the difference between a battery and a charged capacitor? http://physics.stackexchange.com/q/32394 It is said that the battery does not have a charge separation on its ...
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2answers
81 views

Calculating effective capacitance of a circuit [duplicate]

Please refer to the image below. The question asks: 'The effective capacitance between terminals A and B in the network shown in the adjoining figure is?' Here is my working: (C5 and C6 connected ...
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2answers
72 views

Charges on capacitor after full charge by battery

When the charging is finished what will be the charge on an ideal parallel plate capacitor ? To be specific what are the charges on different faces of the 2 plates ? All the books say, after 100% ...
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1answer
12 views

Phase angle of a circuit

Above is the problem at hand. I know how to calculate the angular frequency and total impedance of the circuit given the information provided. However, I'm not really sure what the question is ...
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3answers
692 views

Why do Capacitor Inductor circuits Oscillate instead of reaching equilibrium?

When the capacitor is fully charged there is a potential difference between its poles and that creates a current. This current would create a magnetic field that is changing in the Inductor (because ...
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2answers
59 views

Parallel Connection of Capacitor

Assume Two Capacitor filled with different dielectrics with dielectric constant $K_1$ and $K_2$ respectively in Parallel connection. Then we have same voltage $V$ on both capacitors. Therefore, ...
2
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1answer
62 views

Visualising current in the LCR circuit

I just went through the theory of the serial LCR circuit. There current and voltage are 90 degrees out of phase with each other. Now I was trying to imagine an animation with just dots. And I ...
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2answers
31 views

How is the capacitor affected?

I know that a capacitor stores electric energy or electric charge and understand how, but I don't understand how the distance and the voltage affects its capacitance (I mean what are the mechanisms ...
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1answer
261 views

Significance of Time constants in LR and RC circuits [closed]

What is the significance of a time constant in a circuit? Is there any use of knowing the time at which the charge in a capacitor is 1-1/e times its total charge? What is special about the capacitor ...
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1answer
60 views

How big of a capacitor would I need to release 5 amps for 0.2 seconds? [closed]

Just what the title says, 5 amps for 0.2 seconds. Please bear in mind that I have absolutely no grasp on electrical wiring, so I would appreciate simple terms. What I need to do is release a burst of ...
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1answer
45 views

Why is $k$ left out of the equation $C_\text{all} = (k\epsilon_0A_1/d) + (\epsilon_0A_2/d)$?

The capacitance of two capacitors in parallel is found using this formula: $$C_{all}=C_1+C_2 \, .$$ Capacitance is $$C=\frac{Q}{V} \, ,$$ and also $$C=\frac{kε_0A}{d} \, ,$$ so can I say ...
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1answer
66 views

Two capacitors in parallel vs series - electric field?

If we have two parallel plate capacitors in parallel, do the electric fields between their plates have to be the same? What happens if we have a coaxial cable of length $L$, which looks like this: ...
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1answer
58 views

What actually happens in a capacitor?

I have this doubt wandering through my mind for a long time. A capacitor, according to the definition of physics, is a charge storage device. In a simple parallel plate capacitor, when electrons ...
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37 views

Capacitors as Energy Wasting?

I am reading a lot of articles about capacitors as the energy storage. Let's consider simple circuitry which contain the battery and capacitor in series. The energy flow from the battery will be ...
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1answer
104 views

Half wave rectifier at high frequency and small amplitude ac signal

This is the picture taken from my oscilloscope where I was just checking how a standard half wave rectifier properties. The yellow one is input signal of frequency 20.5KHz and peak to peak value is ...