# Questions tagged [capacitance]

The ability of an object to store electric charge.

1,699 questions
Filter by
Sorted by
Tagged with
103 views

### Net bound surface charge density of capacitor

Q. In a parallel plate capacitor, two dielectric slabs of thickness 5 cm each are inserted between the plates and a potential of 100 V is applied across it. The value of the net bound surface charge ...
1 vote
34 views

### How to determine current as a function of time in an RLC circuit with variative capacitor?

I was given this problem: The image shows an RLC circuit which consist of a constant voltage source $\varepsilon$, an inductor with inductance of $L$, a resistor with resistance of $R$, and a ...
35 views

### Does the Casimir force also define a 'casimir capacitance?'

If you have two plates with distance $\Delta d$ then a Casimir-force will exist between the plates. In contrast if you have two other capacitors with charge $+Q$ and $-Q$ there will be also a force (...
1 vote
196 views

### Why is the field inside a capacitor not the sum of the field produced by each plate?

In this answer by David Z, we can read, When discussing an ideal parallel-plate capacitor, $\sigma$ usually denotes the area charge density of the plate as a whole - that is, the total charge on the ...
1 vote
103 views

### How can this circuit be simplified in the first moments after the circuit breaker closes?

The book states that in this circuit after the transient the branch with the capacitor can be ignored while the branch with the inductance can be considered constituted only by a resistance. This ...
13 views

### An RLC series circuit with current equal to one half the resonant current [closed]

Consider a RLC circuit coupled in series supplied by the AC voltage v= 30 sin(w t), R=50 W, L= 600 mH, frequency f=5 kH. The inductor is a solenoid and the capacitor has cylindric configuration. The ...
25 views

### Does the current inside a capacitor with dielectric becomes zero, if a DC (constant)voltage is applied?

Imagine a capacitor with dielectric with conductivity $\sigma$ and constant voltage source with voltage applied say $V$ is applied to it's ends, now using Ohm's Law we have $\vec{J} = \sigma \vec{E}$....
12 views

### Charges on conducting shell with a conducting sphere inside it

If I have a spherical capacitor which is composed of a conducting sphere surrounded by a conducting shell and the space between them is filled with a dielectric , I assumed that the charge on the ...
1k views

### Diode-Resistor-Capacitor Circuit Equations

So I took the time to measure the current dependency on voltage of a diode I have. I applied an exponential fit to it, and have a pretty reliable equation (within 1%). I'm interested in how a diode-...
28 views

### What is $Q$ in the energy stored in a parallel plate capacitor?

If we have a parallel plate capacitor like the one below the energy stored in it can be give by $$U=\frac{Q^2}{2C}$$ $\bullet$ C is the capacitance of the capacitor Now is the $Q$ the free charge on ...
688 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 ...
1 vote
87 views

### When two capacitors are connected in parallel, do they drain battery quicker?

My question is actually my answer to a question I asked myself i.e 'how does potential difference remain same for both capacitors which are connected in parallel, and not get distributed' When 2 ...
8 views

### What is the capacitance of ferrodoxin molecule?

On Wikipedia it says that a ferrodoxin molecule is a biological capacitor which transfers electron to change the oxidation state of iron from $\text{Fe(II)}$ to $\text{Fe(III)}$. Now I simply want to ...
30 views

### Work done by battery [closed]

In charging a capacitor to a charge $Q$ Is there an equivalent to this in setting up current through an inductive circuit? Energy stored in inductor $= 1/2Li^2$ What would be the work done in setting ...
668 views

### How Are Electromagnetic Waves Produced?

How EM waves are produced say by a capacitor of an LC circuit here if $E$ is increasing in upward direction? My thoughts Thought 1:- If E is increasing E flux is increasing thus B field must be ...
228 views

### Maximum charge of a capacitor

Suppose we have a capacitor charged with charge $Q1$ Then an electron beam hits the positive plate of the capacitor, thus increasing the charge of the capacitor (the battery will begin to deposit the ...
34 views

### Why bridge rectifier circuit is widely used to make power supply? [migrated]

Why bridge rectifier circuit is widely used to make power supply?. which is better, bridge rectifier with capacitor or without capacitor?
1 vote
41 views

23 views

### Can you increase capacitance of capacitor by sandwiching a high dielectric constant material between two strong insulators?

My very limited research into dielectric materials has suggested that the higher the dielectric constant of a material, the less insulating it is. So why not just have some material with extremely ...
53 views

### Disagreement in the magnetic field inside a capacitor depending on the Maxwell equation

Consider a capacitor of two parallel circular plates of radius $a$ separated by an air gap of width $d$, where $d \ll a$. The capacitor is connected an alternating voltage source, $V = V(t)$. To find ...
68 views

### What does equivalent capacitance in general mean?

If you have some capacitors in series then their EC (= equivalent capacitance) means the capacitance of the capacitor which will store the same charge as any individual capacitor in the series when ...
25 views

### Power equation in railgun operation?

In a capacitor discharge through a plain resistor, the capacitor power supplied at any instant is VI; the power dissipated in the resistor is I²R. So VI = I²R. Consider a railgun operated with a ...
62 views

### Potential energy of parallel plate capacitor

I am trying to calculate the electrostrictive strain S on a parallel plate capacitor. For that, I use Young's modulus Y and the formula $$S = \frac{F}{AY}$$ Since the area A and the Young's modulus ...
22 views

### Heat dissipated in a capacitor network on switching a key

Suppose we have this capacitor network connected to a battery($V$) with the switch initially open. On closing the switch whilst keeping the battery connected, we find that some heat is dissipated. We ...
38 views

### Capacitors and electrical energy [duplicate]

We know that the potential energy stored ina capacitor connected to battery of emf V is: (1/2)QV . But the work done by battery in the process is QV where does the half goes ?
230 views

### Does insulating sphere have a capacitance?

A conducting sphere with radius $r$ has capacitance $C=4\pi \epsilon_0 r$. This can be derived as follows: $$C=\frac{Q}{V}=\frac{Q}{\frac{Q}{4\pi \epsilon_0 r}}.$$ Now I am wondering if this ...
I'm solving a differential equation of the form $$200q'+\frac{200}{3}q=3U_o-6U_6+3U_{12}$$ Where $U$ is the Heaviside step function. $q(0)=0 [Coulombs]$ After solving it, I get that at time $t=18$ ...