Questions tagged [capacitance]

The ability of an object to store electric charge.

Filter by
Sorted by
Tagged with
0
votes
0answers
36 views

Charging a single plate of a capacitor does not work

I charged a 100nF capacitor with 12V with a battery, then i disconnect the battery from the capacitor and connect the positive side of the capacitor to ground (which is an electron source) ...
0
votes
1answer
19 views

Relation between initial current and current amplitude in $RLC$ circuits

Let $\phi$ be the so called phase-angle, which measures how much the voltage $V(t)$ leads the current $i(t)$ in a $RLC$ circuit. How would you justify the relation $$i(t=0)=i_m\cos\phi$$ where $i_m$ ...
4
votes
2answers
66 views

How come the filled water bottle work as a stylus for phone but not the empty bottle?

Take an empty plastic bottle, and make it slide on a mobile screen. You would find that it's not doing anything. Now filled up this bottle with water and try doing the same. This time you will find ...
5
votes
7answers
411 views

How does current flow in a circuit with a capacitor?

When a capacitor is connected to a battery, current starts flowing in a circuit which charges the capacitor until the voltage between plates becomes equal to the voltage of the battery. Since between ...
0
votes
0answers
35 views

Energy loss due to changing capacitance [closed]

I was able to solve first two parts of the question. But after solving third part (energy loss to be precise), I felt conflicted. I calculated that Uinitial = 0.0162 J and Ufinal = 0.0162 J So then ...
0
votes
1answer
44 views

I am confused on how to think about potential energy stored in capacitors [duplicate]

Energy stored in capacitors is represented by $$U = \frac{1}{2} QV$$ Now I have heard 2 reasons why there’s a half factor, unlike the general potential energy equation, which is $U = QV$. Capacitors ...
0
votes
0answers
18 views

Capacitive circuits with two or more potential differences

Just I was curious on this question that I like very much. Here I add my image create with my fingers. Recently I have been looking at the Physics textbooks that I have, including that of the ...
1
vote
1answer
24 views

How to identify series and parallel connections of capacitors in complex circuits? [closed]

Like for this question (picture attached) how to identify if capacitors are in series or in parallel?
1
vote
2answers
42 views

Does energy of a capacitor means energy stored in both plates?

I've a doubt in this, Does the term potential energy of a parallel plate capacitor means the energy stored in both the plates or a single plate, since the formula $E=Q^2/2C$ , $Q$ is the charge of ...
0
votes
1answer
32 views

If there's a capacitor fully charged and the other isn't fully charged a and they are in parallel are the tension in the two capacitors equal? [closed]

V is the final tension of the second capacitor, but the other one isn't fully charged and both of them are in parallel, are the tension of the two capacitors equal?
-1
votes
0answers
21 views

What is the Initial tension in a equivalent capacitor? [closed]

In the equivalent capacitor of this association, what's the initial tension of the equivalent capacitor? $V_0$ is the initial tension.
0
votes
1answer
23 views

Work done on a charge inside a homogeneous electric field and changes in Energy of the system

How to understand the concept of work using the following example: a positively charged particle (with charge $Q$) is placed in between a charged in a homogeneous electric field between the capacitor ...
1
vote
1answer
45 views

Does work done in a capacitor in moving a charge or increasing potential difference always twice the potential energy stored?

On doing calculations like this: Work done in moving a charge across a potential difference = $(CV)V$ = $CV^2$ Potential energy increased = $(1/2)CV^2$ From this work done is twice the potential ...
1
vote
7answers
161 views
+50

Why do we treat the whole capacitor as if it would be a single conductor?

I am a high schooler and I am very confused regarding redistribution of charges when we connect 2 capacitors; my problems are: Question 1.1 Why do we treat a whole capacitor as if it is a single ...
0
votes
0answers
42 views

Conversion of Maxwell's Equations to Ohm's Law

I am working on electric currents in Comsol and have the following set of simplified equations: $$ \nabla \cdot \mathbf{J} = Q_{j,v} \\ \mathbf{E} = -\nabla V \\ \mathbf{J} = \sigma \mathbf{E} + \frac{...
3
votes
3answers
156 views
+50

'Simple' capacitor problem

I posted this question because I have a problem in grasping the connection between force on a charge and voltage potential equilibrium. So the problem is the next: we have a charged capacitor ...
0
votes
2answers
24 views

Electric field due to a large, non-conducting plate and factors of 2

I'm trying to derive the electric field due to a single large, thin, non-conducting plate at a point (see figure). I'm solving it using 2 methods, and arriving at a different answer using both. I've ...
0
votes
2answers
46 views

Is battery a capacitor that's being continuously charged?

Is it correct to say that a battery is like a capacitor which keeps being charged?
0
votes
0answers
40 views

Finding the surface charge density in the following system of conductors and charges [closed]

Two infinite conducting plates 1 and 2 are separated by a distance $l$. A point charge $q$ is located between the plates at a distance $x$ from plate 1. Find the charges induced on each plate. I am ...
0
votes
1answer
43 views

Electric field component in a capacitor with dielectrics inserted partially

In the above set up I have two oppositely charged capacitor plates seperated by a distance 'd' with half of the region between filled with a dielectric material of constant $K$ and the other half in ...
0
votes
1answer
82 views

Why do two approaches to this capacitors problem give two answers? [duplicate]

I came across a capacitors problem that seemed to be very simple, but I can't figure reasoning as to why two approaches to the problem yield two different answers. One of them is wrong, but I can't ...
0
votes
1answer
24 views

In a capacitor there are four dielectrics filled [closed]

In a capacitor there are four dielectrics filled as shown in the figure, and we are required to find the equivalent dielectric constant. So I approached it by taking $K_1$ and $K_2$ in series and $K_3$...
1
vote
0answers
7 views

What would an optimally designed (maximising the capacitance) capacitor look like?

I've just finished the chapter about capacitors on my textbook, and I have a question. So, there are problems in my textbook where the capacitance of different arrangements of charged surfaces is ...
0
votes
2answers
26 views

Intuition behind this technique to find capacitance between an infinite conducting plate and any other body

I am not looking for the answer to this question but looking to understand the concept behind this question. In Irodov problem 109 under electrodynamics , we are asked to find the capacitance between ...
0
votes
2answers
38 views

Energy stored in a Capacitor with dielectric [closed]

We have a parallel plate capicitor with capacitance C ($ C= \epsilon°A/d $) when no dielectric is inside it. The charge on it is Q(+Q on left and -Q on right). Now a dielectric slab of dielecteic ...
1
vote
1answer
44 views

How to solve when circuits have both d.c, and a.c. component?

The given figure illustrates the simplest ripple filter. A voltage $V=V_0(1+\cos(\omega t))$ is fed to the left input. Find the output voltage V'(t). As it can be seen that the voltage fed to the ...
0
votes
0answers
8 views

Does earthing a Circuit junction doesn't cause flow of charge from it?

In a question related to circuit of capacitors, my book didn't considered flowing of charge from the juction which is earthed. Instead it applied conservation of charges there.$C$ and it is earthed" />...
1
vote
1answer
20 views

The physics behind DC voltage derating of capacitance

I don't understand this phenomena pointed out in LDO's Capacitor vs. Capacitance where it says: Given the dynamic nature of capacitors (storing and dissipating electric charge in a nonlinear fashion),...
0
votes
0answers
17 views

What's the electric field inside a capacitor with AC current?

In DC-circuits the Electric field can be easily calculated under the conditions the field is homogeneous: $U = \int E \,\mathrm{ds} = E\,d$. Now I wonder what if you apply an alternating Voltage $U(t)...
0
votes
1answer
26 views

Does $\epsilon$ in the formula for capacitance correspond to the the permettivity of the body or the surroundings?

In the formula of the capacitance of spherical shape, $C = 4\pi\epsilon R$. Is $\epsilon$ the permittivity constant of the region around sphere or it is that of the material of the sphere?
1
vote
5answers
77 views

Where is energy in energy density?

I was learning about energy density and it seemed to be defined as the potential energy per unit volume in an electric field $\frac{dU}{dV} = \frac{1}{2}\epsilon E^2$ But how can just the electric ...
2
votes
0answers
27 views

Tilted metallic plate touching two capacitor plates

A parallel plate capacitor of capacitance $C$ is as shown. A thin metal plate A is placed between the plates of the given capacitor in such a way that its edges touch the two plates as shown. Find the ...
1
vote
2answers
67 views

Purely resistive AC circuits [closed]

Is it possible to have a purely resistive RC circuit? Recently came across a question: A 130Ω resistor and a 40μF capacitor are connected in series to an AC source of frequency ω. For the combination ...
1
vote
3answers
47 views

Why do resistors in parallel with uncharged capacitors get eliminated from the circuit?

I was doing a problem where I was asked to find the current in an R-C circuit 'just after' the switch had been closed i.e at t = 0. All of the capacitors are initially uncharged. Could someone explain ...
0
votes
1answer
34 views

Charging capacitor, Relaxation time - obtained experimentally and theoretically [closed]

In the shown circuit, I was measuring how the voltage on capacitor $V_C$ changes with time. The theory says that $V_C(t) = V_T(1- e^{-t/R_1C})$, where $V_T$ is voltage on battery. If I plot my ...
2
votes
1answer
44 views

Capacitor with multiple dielectrics [closed]

Let's say there is a capacitor as shown in the figure, $K_1$, $K_2$, $K_3$, $K_4$ being the dielectric constant of each quadrant. (the dimensions of all four parts are equal.) Let $C_1$, $C_2$, $C_3$,...
2
votes
3answers
104 views

A strange electric field, can it exist? [duplicate]

If the electric field strength is $E_x=x, E_y=E_z=0$, then by $\nabla\cdot E=\frac1{\epsilon_0}\rho_e$ where $\rho_e$ is the density of charge, we get $\rho_e=-1$ for any point in the space. But if $\...
2
votes
1answer
51 views

Charges on a surface

Suppose we have a cylinder with uniform density and radius A. A conductor cylindrical shell with inner radius B and outer radius C is axial to the cylinder and involves it. Between the solid cylinder ...
1
vote
2answers
58 views

Charging capacitor, with series and parallel resisters

I understand how equations for charging capacitor are derived and what they represent. But here is my problem: if you want to experimentally see how voltage on capacitor changes with time, you have to ...
1
vote
2answers
79 views

On solving an RC circuit [closed]

Given the following RC circuit: it's required to calculate how the electric current varies and how the other electrical quantities vary. Based on that request, I was wondering if it was correct to ...
0
votes
1answer
20 views

Finding Mutual Capacitance of Two Identical Metal Spherical Balls?

It is a question from the Irodov: Find the capacitance of a system of two identical metal balls of radius $a$ if the distance between their centres is equal to $b$, with $b >> a$. The system is ...
0
votes
0answers
16 views

Energy stored in a capacitor and limit

Suppose a capacitor made of two concentric spheres. The outside has radius $a$, and the inside sphere has variables radius $b$. We need to find the radius $b$ in such way that the energy stored by the ...
1
vote
1answer
25 views

What does annihilation of charges mean?

Say you had two (parallel plate) capacitors that were initially charged to unequal charges. If you connect these capacitors in parallel such that the positive terminal of one plate is connected to the ...
0
votes
2answers
26 views

Potential across the capacitor in LC Circuit [closed]

Below is the circuit as an example. Situation: Initially the Switch $S_1$ is closed for a long time and circuit comes to steady state. Now, consider t=$0$ and the switch $S_2$ is closed as well as $...
1
vote
1answer
42 views

Electric field between two parallel plates

In my class we derived an expression for an electric field due to an infinitely long plane of charge and it given as: $$\bf{E} = \frac{\sigma}{\epsilon_0}\hat{\bf{r}}$$ where $\sigma$ it is the ...
1
vote
0answers
9 views

Term of dielectric constant in the expression of induced charge density dielectric medium kept in between the plates of parallel plate capacitor

Whenever a dielectric substance is kept in between the plates of a parallel plate capacitor, it gets polarized and there is a net electric field developed which reduces the electric field between the ...
0
votes
1answer
47 views

How are charges distributed on a capacitor in the following circuit?

Four metallic plates are used to form two identical capacitors as shown in the figure. Initially the plates were uncharged. Two batteries of different emf are connected as shown. We have to find the ...
1
vote
0answers
28 views

How can you solve the equation for a non-concentric cylindrical capacitor?

I am having some trouble figuring out how to start this problem, I know in order to solve the problem itself I have to find an answer to Laplace's equation, that will give me the potential of the ...
-1
votes
2answers
64 views

If electric field outside a parallel plate capacitor is zero then how does it stop charging after some time?

Many sources state that “charging of a capacitor stops when potential difference across a capacitor is equal to that of the battery”. But I cannot understand how this is the reasoning as, an electron ...
0
votes
1answer
23 views

Between 2 electrically charged plates, can the speed of particle depend on distance between the plates? (Refer to image)

Now I understand that $\text{work}=KE$ and this will give the formula for speed as $$v=\sqrt{\frac{2qV}{m}}$$ My question is can’t the $V$ be replaced by $Ed$ since $V=E/d$?

1
2 3 4 5
32