The ability of an object to store electric charge.

learn more… | top users | synonyms

2
votes
0answers
232 views

Calculating Electric Field from a Potential Difference w/o Charge

So here is my homework question: Two long cylindrical shells of metal (radii $r_1$ and $r_2$, $r_2 > r_1$) are arranged coaxially. The plates are maintained at the potential difference ...
0
votes
0answers
80 views

What is the electrical field of a capacitor plate as a charge approaches

The electrical field for a charge density $\varrho(r)$ is $${\bf E}({\bf r})=\frac{1}{4\pi\varepsilon_0}\int \varrho({\bf r}')\frac{{\bf r}-{\bf r}'}{\hspace{.1cm }|{\bf r}-{\bf r}'|^3} \mathrm ...
1
vote
1answer
1k views

Difference between voltage and potential energy in a capacitor

I'm confused about the difference between voltage and potential energy in a capacitor. Suppose you have a capacitor with a voltage V and capacitance C, and you release a particle with charge $+Q$ from ...
-3
votes
1answer
82 views

combination of 5 identical capacitors [closed]

Given 5 identical capacitors, each EMF. Draw the proper combination of all these 5 capacitors.. 1.) 2.5 2.) 4.17 I really do not know how to solve this thing and if anyone of you knows the title of ...
1
vote
2answers
1k views

How capacitive is the human body?

Testing a capacitive screen, it's clear that it can tell the difference between a celery touching it (human holding it with an isolating material) and a human touching it. Touching it holding a ...
1
vote
3answers
125 views

Will the rms current be affected by inserting dielectric in the capacitor in an LCR circuit?

MY thoughts: I think it will not be as the expression for RMS value is dependent only on the peak value of current. Is my thinking correct?
1
vote
2answers
71 views

Capacitor's voltage

Imagine I have two plates that form a capacitor, so the magnitude of the charge in each plate is, let's say, $Q$. So, the force, in respect to the distance $d$, is gonna be: $$F(d) = ...
1
vote
1answer
175 views

Is this a series or parallel connection?

I am confused how the capacitors in this circuit are connected. $C_4$, $C_6$ and $C_5$, $C_3$ appear to be parallel, but both $C_4$ and $C_6$ seem to be in series with $C_1$ as do $C_5$ and $C_3$. Am ...
2
votes
1answer
277 views

$\pi/2$ phase shift in RC circuit

I just recently learnt Alternating Current and RCL circuits and I also learnt about phasers and various graphs. Now I also know that current lags in an LR circuit. My intuitive understanding of this ...
3
votes
2answers
167 views

Moving the plates of a charged capacitor to calculate energy density - where's the flaw in my argument?

For a charged air-dielectric capacitor, let the plates be parallel to the $xy$ plane, with the top carrying a positive charge $+Q$, the bottom a charge $-Q$. The force on an infinitesimal charge ...
3
votes
3answers
483 views

The moving capacitor

To what extent can a charged capacitor mounted on a moving platform (e.g. a rotating wheel) be considered an electric current generator? Electric current, after all, is nothing more than the transport ...
0
votes
1answer
170 views

Drawing the circuit from a differential equation

Can you please help me in modelling a circuit using the differential equation? In the following equation, $u(t)$ is the input voltage and $y(t)$ is the output voltage. ...
0
votes
1answer
652 views

Voltage and parallel-plate capacitors

Suppose we have two parallel plates (each of area $A$) spaced with distance $d_1$ acting as a parallel-plate capacitor within a circuit. If the capacitor is connected to a power source with constant ...
2
votes
1answer
250 views

A dielectric table is being inserted between a plate capacitor and $\triangle U<0$ how to deduce the table is attracted to the plates?

I am practicing for an exam in my Physics $2$ course. One of a previews exam questions described a plate capacitor and asked to calculate the initial energy $U_{0}$, then a dielectric table was ...
0
votes
2answers
237 views

Is $Q=CV$ still acceptable formular on the capacitor charged by the transformed circuit?

Assume there is a 100V to 1000V transformer and the capacitor connected in the second circuit.(You know, transformers have two circuits) The second circuit's voltage is 1000V, but the amount current ...
2
votes
1answer
1k views

Difference between parallel and series capacitors

Basically, I can't figure out that whether a capacitor is connected in series or parallel. The same problem occurs while solving for resistors. Can someone help me understand this difference ...
0
votes
1answer
114 views

Capacitance from Maxwell's equations

I am trying to get the definition of capacitance nailed down. This is my work so far: $$ \frac{\mathrm{d}U}{\mathrm{d}t} = \frac{\mathrm{d}}{\mathrm{d}t} \int_{\Omega_a}{ u(\mathbf{x},t)\mathrm{d}t} = ...
2
votes
1answer
396 views

Graphene batteries/super capacitors

A while ago, there was some news about micro-scale graphene-based supercapacitors and these devices can charge and discharge a hundred to a thousand times faster than standard batteries. Question: ...
0
votes
2answers
278 views

Drawing electric field lines-Equations or software

Shown below in the diagram are two conducting material connected to a battery source and vacuum OR air is in between them. There will be charges developed on their surfaces. I am interested in finding ...
2
votes
1answer
555 views

Electric field in a capacitor with a dielectric with variable permittivity

Consider the following parallel-plate capacitor, with a potential difference of $V$ across it's plates: I've seen some problems that assume a dielectric with a variable electric permittivity of ...
1
vote
2answers
571 views

What are the advantages in using 2 identical capacitors?

What advantage might there be in using two identical capacitors in parallel connected in series with another identical parallel pair, rather than using a single capacitor?
1
vote
3answers
286 views

Which is more dangerous upon contact, series or parallel capacitors?

If a pair of capacitors were connected up in series, and an identical pair was connected in parallel which pair would be more dangerous to handle if connected to the same voltage source?
1
vote
1answer
521 views

Dipole moment induced in a spherical particle

Consider a spherical metal particle made out of gold. If there is an external charge somewhere near the gold particle, is there a way to calculate the resulting dipole moment that is induced by the ...
1
vote
1answer
123 views

Dielectric modification of electrostatic equations?

I have learnt that in cases of electrostatic fields inside a dielectric of any source charge, the field is reduced by a factor of K( if K, the dielectric "constant", is taken everywhere to be same). ...
0
votes
1answer
176 views

Electrons drift velocity and capacitors

My friend said this to me and just want to make sure this is right " when we connect the a battery to a LED and the 2 poles are connected, electrons flow from the (-) to the (+) but with very low ...
0
votes
1answer
131 views

One terminal of an ideal voltage source connected to earth->Massive current will flow?

Assume we have a "somewhat" ideal voltage source like a DC power supply powered by mains. Take just one terminal and form a conductive path between it and earth ground. Assuming that no conductive ...
-2
votes
1answer
130 views

Source of potential energy in a capacitor being pulled apart

When the plate spacing is large the capacitor system is storing more energy than when it is small. If one manually changes the spacing, where does the additional energy "come from" as the plate ...
0
votes
4answers
107 views

Capacitors' working in a circuit

Does charge in a capacitor containing circuit stop flowing when the potential of the capacitor becomes equal to the potential of the battery??
1
vote
1answer
280 views

Energy Change in a Capacitor by Inserting Dielectric

This is a practice Physics Subject GRE problem. A parallel-plate capacitor has plate separation $d$. The space between the plates is empty. A battery supplying voltage $V_0$ is connected across ...
2
votes
4answers
2k views

Potential Difference Between Capacitors in Series

I am struggling to find an answer to this, hopefully relatively simple, question. I had a search on stackexchange but couldn't find anything helpful. We are learning about capacitors in Physics and I ...
4
votes
2answers
460 views

Equivalent RC circuit to a RRC circuit?

I'm in doubt about a situation that I've seen sometimes: imagine we have a resistor in parallel with a resistor and a capacitor in series. Since I don't know how to generate figures of circuits to ...
1
vote
1answer
160 views

Capacitance of a conducting disk

I'm reading this(PDF) derivation of the capacitance of a thin conducting disk. The surface charge density of such a disk can be shown to be: $\sigma(r) = \frac{Q}{4\pi a\sqrt{a^2 - r^2}}$ (in ...
1
vote
4answers
3k views

Capacitor Charging and Discharging when connected to the ground

When we charge a capacitor using a battery and then remove the battery, the plates of capacitor becomes charged. One holds positive charge and the other one gets equal negative charge. o. k. ? Now ...
0
votes
0answers
60 views

Capacitors discharging in series [duplicate]

If you connect positive plate of a charged capacitor to ground, it doesn't get discharged. Now consider $4$ capacitors of equal capacitance connected in series to a $10\, \mathrm{V}$ battery. Connect ...
2
votes
1answer
494 views

How we approach RLC circult from RLGC model?

In the text, it introduces a practical model to investigate a transmission line (like BNC cable), it considers the transmission line has resistive $R$, inductance $L$, conductance $G$ and capacitance ...
1
vote
1answer
279 views

Finding the Steady State Charges

Here the problem states to find the steady state charges on the condensers.<<<< According to me the charges on second at steady must be ...
0
votes
1answer
35 views

Work due to introducing a dieletric in a capacitor

I have a doubt about a couple of exercises tha asks to find the work done on introducing a dieletric between the plates of a capacitor. Yes, this question is in the general case, how do we procede? I ...
0
votes
2answers
2k views

Inserting metal into parallel plate capacitor

The plates of an isolated parallel plate capacitor with a capacitance C carry a charge Q. The plate separation is d. Initially, the space between the plates contains only air. Then, an ...
1
vote
2answers
129 views

Flashlights and Capacitors

Why capacitors are used in flashlights of cameras instead of attaching the light directly to the battery? How this leads more light?
5
votes
4answers
407 views

Energy Gain with capacitor?

I have a question about energy gain in capacitors. Assume the following system: As the electron gets accelerated inside the capacitor, it will have more kinetic energy coming out than going in. But ...
0
votes
3answers
3k views

Why does the area of the plates affect the capacitance?

Why does the area of the plates affect the capacitance? Lets say I have a parallel plate capacitor with a charge of 10C and a potential difference of 5V. By the definition $C=Q/V$, the capacitance is ...
0
votes
1answer
190 views

Potential of a conductor depends on the size and shape of the conductor. How?

1) When a charge 'q' is given to an isolated conductor, its potential will change. 2) The change in potential depends on the size and shape of the conductor. I could understand the point no. 1. ...
1
vote
2answers
95 views

Where are exactly the charges of charged capacitor?

If a capacitor is connected to a battery and is charged, are there charges inside the wires or do they just accumulate on the surfaces of capacitor?
1
vote
2answers
142 views

Why isn't this capacitor charging?

Let's say you have a parallel plate capacitor and you connect one plate to the positive terminal of a battery and the other plate to the negative end. So this is like a static situation, you have a ...
2
votes
3answers
427 views

Can I charge a capacitor using 2 batteries?

1 capacitor, 2 separate batteries (Battery A and Battery B). Connect A+ to one side of the capacitor and B- to the other side of the capacitor. A and B are not connected, there is no closed circuit. ...
5
votes
2answers
671 views

Why does a capacitor discharge?

Suppose a charged capacitor (parallel plates), the negative and positive charges on two plates attract each other. Which force cause the negative charge carriers (electrons) move through the circuit ...
1
vote
1answer
600 views

Calculate Capacitance in Series AC Circuits?

I'm supposed to calculate the capacitance of an unknown capacitor in series, but I'm not sure exactly which equation to use. I know the voltage across the resistor (Vr), voltage across the capacitor ...
1
vote
1answer
460 views

Parallel capacitors without battery. Does charge flowing after a dielectric input?

If I charge two capacitors which are connected parallel $[$the minus (-) of the one opposite to the minus (-) of the other and the plus(+) of the one opposite to the plus (+) of the other.$]$, will I ...
0
votes
1answer
348 views

Non conducting charged planes

I have two parallel non conducting charged planes with opposite charges $6\mu C/m^2$, area $A = 3m^2$ and distance between the planes $d = 0.004 m$. I know the potential between these two planes is ...
2
votes
1answer
443 views

Two capacitors sharing charge

My two capacitors:                               I have these two capacitors ($C_1 = 3\mu F, C_2 = 4\mu F$) both initially under 19 volts. Then, I added a dielectric with $k=4$ at $C_1$ and entire ...