The ability of an object to store electric charge.

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64 views

Intuitive explanation for uniform electric field between capacitor plates

Could anyone explain why the intensity of the electric field between plates of a charged capacitor is constant? Moreover, the varying the distance between plates doesn't change the electric field ...
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4answers
5k views

Why is water not used as a dielectric in the condenser?

The dielectric constant of water is very high. Then why is it not used as a dielectric in the condenser?
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1answer
44 views

Why don't charges build up on wires like plates of a capacitor?

Suppose you have a parallel plate capacitor and you want to charge it by using a battery. You will connect the plates with the two terminals of the battery. Now my book says that the charges will get ...
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1answer
107 views

Discharging capacitor

When the capacitor is fully charged and the switch as it B, how can we apply KVL at that loop to reduce the equation to (-IR)? Why is it negative? At time = 0 is the current not zero? And it will move ...
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1answer
195 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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1answer
22 views

Connecting spheres of different capacitance

If I connect a sphere of capacitance $C_1$ to a charged sphere of capacitance $C_2$, will the charge be distributed evenly on both spheres (is the charge density going to be equal on both spheres?). ...
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2answers
242 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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0answers
34 views

Capacitance as integral of electric field [duplicate]

My question refers to part of Ex. 1.17 in Jackson, 3rd Ed.: A volume $V$ in vacuum is bounded by a surface $S$ consisting of several separate conducting surfaces $S_i$. One conductor is held at ...
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1answer
24 views

What would occur between the parallel plates of the capacitor?

In capacitors dielectric materials are sometimes inserted between the parallel plates. What would happen if a diamagnetic, or a paramagnetic material is inserted between the parallel plates of a ...
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2answers
151 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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0answers
32 views

How to solve this problem [closed]

Two capacitors have capacitances of 5.0 µF and 4.5 µF. Initially, the first one has a potential difference of 17.0 V and the second one 6.5 V. If the capacitors are now connected in parallel, what is ...
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1answer
131 views

Charged dieletric/conductor in capacitor

It is a standard problem to consider a dielectric or a conductor between the parallel plates of a capacitor. But what happens to capacity, voltage, charge, inserting between the plates of an ideal ...
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1answer
1k views

Calculating capacitance of integral PCB components

I posted this question originally with Electrical Engineering Stack Exchange but nobody seems to know the answer. So I thought a physicist might find the question more approachable. Formulas for ...
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4answers
260 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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2answers
177 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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0answers
26 views

What is meant by short circuit in capacitor?

I can't understand the mechanism of short circuiting in a capacitor. How will it come to know me that the capacitors are short circuited
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3answers
82 views

Spherical Conducting Shells, Potential

When we have a spherical conducting shell and charge on outer surface of the shell then the potential inside remains constant i.e, kQ/R (R=radius). But say the inner surface of the shell is charged ...
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0answers
28 views

Capacitors in space [closed]

I'm new here and I have a question for all of you. What happens to a capacitor in open space? There are different kind of them, which one of these is better to use there? And... We know that if we ...
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0answers
36 views

How inversion layer shields electric field?

This question is somewhat relating to electronics but I think it fits better with physics. The leccture here (slide 13) shows that the gate to body capacitance (Cgb) in linear region is 0. However, ...
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2answers
74 views

Discharging a capacitor

Suppose I have a charged capacitor, meaning there's a voltage (electric potential difference), say, $2V$, between its two plates. We don't know the electirc potential of the individual plates, right? ...
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3answers
7k views

Electric field intensity in a dielectric inside a capacitor

In the question A parallel plate capacitor is charged from a cell and then isolated from it. A dielectric slab of dielectric constant $K$ is now introduced in the left half region between the ...
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1answer
108 views

What does “Receptor” convention refers to in RC circuits?

my question is How can we choose the convention in a circuit and what does it refer to ? Especially for a Capacitor I hear the terms "passive sign convention..." "receptor convention ..." "generator ...
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0answers
31 views

Regarding the zero internal electric field in a conductor (electrostatic case)

Let's say we have a homogenous electric field in the $z$-direction. For computational simplicity let's say we have a thin sheet of metal covering entire the $x$-$y$ plane. The answer here is straight ...
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2answers
76 views

Energy changes due increasing plate separation of unconnected charged capacitor

If a capacitor is charged by a source with constant voltage, $V$, the energy, $W$, stored by a capacitor of capacitance $C$ is given by: $$ W = \frac{1}{2} QV = \frac{1}{2} V^{2}C = \frac{Q^{2}}{2C} $...
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1answer
183 views

What happens when two charged capacitors are joined?

Two capacitors are charged and then they are connected with a wire. Then what will become constant after they are connected? Their potential or their charge? Exact question: A capacitor $2C$ is ...
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0answers
18 views

How are the charges on the plates of a capacitor distributed?

Given a specific overall amount of energy a rectangular parallel plate capacitor stores what number of atoms on a specific plate would have any given specific charge?
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4answers
183 views

Why is the total potential difference in a circuit the sum of the individual potential differences?

I am having difficulty in applying my understanding of electrical potential to circuits. Why is the total potential difference in a circuit the sum of the individual potential differences among ...
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1answer
20 views

By which equivalent circuit (RC serie or RL serie) can I substitute the following circuit?

I was trying to solve the following question: "Assuming that 𝐑 = 𝟏𝐤𝛀, 𝐂 = 𝟏𝛍𝐅, 𝐋𝟏 = 𝟔𝐦𝐇, 𝐋𝟐 = 𝟑𝐦𝐇, 𝐞 𝛚 = 𝟏𝟎𝟒 rad/s, tell if the circuit can be substituted by an equivalent RC ...
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2answers
113 views

Capacitor/Inductor Resonance

I am struggling to understand the concept on resonance in electric circuits. I understand that a inductor builds up a charge on it, then the current flows to the capacitor, charging it. But then ...
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1answer
81 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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1answer
50 views

What happens when an AC source is connected to a capacitor and a LED?

When a DC source is connected to a capacitor and a LED, and the voltage is removed when capacitor is charged, the capacitor supplies current to it for some time. What happens if this DC source is ...
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4answers
94 views

Which makes for a better equivalent capacitor? In series or in parrallel? [closed]

I understand how capacitors in series and in parallel work. However, I am wondering if it makes a difference, in terms of making a better capacitor that can store more charge, would you connect them ...
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1answer
37 views

Principle of mutual capacitive touch screen

I'm curious about how the mutual capacitive touch screen works, so I did some research on internet and found an excellent explanation: youtube video. According to the video, this is how the mutual ...
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0answers
23 views

Circuit with capacitor and battery- why same voltage?

If we connect a capacitor and a battery in the same circuit, what makes the charge move until the voltage on the capacitor is the same as voltage on battery?
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0answers
53 views

Minus sign in analyzing RC with changing emf circuit?

I'm learning electromagnetism from Purcell's book. He say that if we have the following circuit: $$-\frac QC + RI = \mathcal E_0\cos\omega t~,\quad I = -\frac{\mathrm dQ}{\mathrm dt} $$ The ...
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1answer
37 views

main cause of self charging of unshorted capacitors?

In the lab, we keep all of the high voltage capacitors shorted when not in use, and rightfully so. They tend to spontaneously charge when left for some time and become extremely dangerous. while the ...
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1answer
263 views

What does an increased time constant of a capacitor do?

If a capacitor is being charged to any voltage, what effect would increasing the time constant have on it and if a graph of Charge Q/Time T was plotted to give a positive decreasing gradient, how ...
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2answers
46 views

How do charges accumulate even though current flows through a capacitor?

I don't understand why do charge accumulate on each plate of capacitor.I learned about displacement current which flows through the gap of the capacitor and this makes the circuit continuous.But why ...
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1answer
31 views

Self-Capacitance of Disc [duplicate]

I was reading a paper today modeling capacitances, and came across self-capacitance of a disc. After skimming google, it looks like this is defined as "the capacitance between the object itself, and ...
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1answer
33 views

Does the charge leakage of capacitors lead to photon emission?

Capacitors will leak charge over time. This charge is basically electrical current leaking through insulating layer of the capacitor. I am wondering, if there is some emission of photons as there is ...
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1answer
29 views

Force between plates of a capacitor with dielectric a battery

My teacher told me that the force will increase $k^2$ times, where $k$ is the dielectric constant, but I don't see how. To start with, with no dielectric, the force between the plates is given by $\...
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4answers
202 views

Can the potential difference produced in Van De Graff generator used to generate electric current?

If this machine can build up high voltages of the order of millions of volts, can we use this voltage to generate a current of electrons? The building up of potential difference can result in an ...
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3answers
26 views

How do you find the charge and potential difference of a single capacitor? [closed]

Here is what the diagram of the capacitors look like: 5.00 µF 6.00 µF ---| |--------| |--- ---| |--------| |---- 2.00 µF 4.00 µF NOTE: The system ...
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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
28 views

Potential difference between two assymetrically charged plates

What is the potential diff between two plates of charges $q_1$ and $q_2$ ($q_1$ $>$ $q_2$)? I know the equation is $V = \frac{q_1-q_2}{2C}$ where $C$ is the capacitance of the system but how has ...
4
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2answers
96 views

What moves the charges between capacitors?

Suppose I charged two capacitors to charges Q1 and Q2. By charging a capacitor to charge +Q , I mean that one plate acquires a net charge +Q and another plate acquires a net charge -Q.The capacitors ...
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0answers
15 views

Electrostatic energy of the system

Problem : $(A)$ There are two thin concentric metallic shells of radius $a$ and $b$ $(b>a)$. Inner shell carries a total charge $Q$ and the outer shell carried a total charge $–Q$. Calculate the ...
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1answer
55 views

Why can't we use a capacitor to detect electrons in the electron double slit experiment?

So, basically I have been learning Quantum Mechanics online and I leant about the double slit experiment with electrons, wherein if you try to detect an electron with a light source having wavelength ...
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1answer
37 views

Force between the plates of a capacitor

As we know that the electric field between two parallel plates of a capacitor is $$E=\frac{\sigma}{\epsilon_0}$$, so the magnitude of force exerted by one plate on the other should have been $$F=QE$$. ...
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1answer
27 views

why potential becomes equal when capacitor are connected

If we have a circuit as shown in which two capacitor are connected of unequal potential. Now if we close the switch the charge will flow till potential becomes equal. But as we know $Q=CV$, $V=Ed$...