What is Capacitor: Definition and 1000 Discussions
A capacitor is a device that stores electrical energy in an electric field. It is a passive electronic component with two terminals.
The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser or condensator. This name and its cognates are still widely used in many languages, but rarely in English, one notable exception being condenser microphones, also called capacitor microphones.
The physical form and construction of practical capacitors vary widely and many types of capacitor are in common use. Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, air, and oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy, although real-life capacitors do dissipate a small amount (see Non-ideal behavior). When an electric potential (a voltage) is applied across the terminals of a capacitor, for example when a capacitor is connected across a battery, an electric field develops across the dielectric, causing a net positive charge to collect on one plate and net negative charge to collect on the other plate. No current actually flows through the dielectric. However, there is a flow of charge through the source circuit. If the condition is maintained sufficiently long, the current through the source circuit ceases. If a time-varying voltage is applied across the leads of the capacitor, the source experiences an ongoing current due to the charging and discharging cycles of the capacitor.
The earliest forms of capacitors were created in the 1740s, when European experimenters discovered that electric charge could be stored in water-filled glass jars that came to be known as Leyden jars. Today, capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits they tune radios to particular frequencies. In electric power transmission systems, they stabilize voltage and power flow. The property of energy storage in capacitors was exploited as dynamic memory in early digital computers, and still is in modern DRAM.
TL;DR Summary: Need dielectric constant for given capacitor
Given a 7.4 pF air-filled capacitor, you are asked to convert it to a capacitor that can store up to 7.4 mJ with a maximum potential difference of 652 V. Which dielectric in Table 25-1 should you use to fill the gap in the capacitor...
I'm delving into the topic of ionization chambers, but as someone without a background in electrical engineering, I'm finding the equivalent circuits a bit challenging to comprehend. Specifically, I'm puzzled by the placement of the chamber's capacitance and any parallel capacitance in the...
I want to ask about question (c). My idea is to compare the period and time constant. The period is 0.05 s and time constant is 0.005 s.
Time constant is the time needed for capacitor to discharge until the charge stored in it becomes 37% of initial charge. But I don't know how to relate the...
I am confused with the equation to be used for capacitor in electrical analysis
The standard equation we have is Q=CV -> 1
the other equation is is V = Z*I ohms law Z is the impedance of the capacitor. Both are giving me voltage, which one to use ?
I simulated the below circuit to capture the phase delay between input voltage and output current in LTSpice
How do i measure the phase delay introduced due to capacitor?
My students build "eCars" that use wheelchair motors and two 12 volt AGM lead acid batteries in series. A pair of Bosch 25Amp, 24 VDC, drill switches control power to each wheel. Tons of fun (see here):
The switches last in some cases for years, but quite a few have burned out the "variable"...
Suppose we have two conductors ( can be of different shapes) and connect them to battery.
Why would equal amounts of charge appear on the two conductors?
Hi,
I am not sure if I have calculated the task correctly
I have now assumed that the capacitor does not need to be charged and is therefore fully charged. In a DC circuit, a capacitor acts like an infinitely large resistor or like an open switch, so I assumed that it is a parallel circuit...
A capacitor consisting of 2 square metal plates placed at a certain distance is connected to a potential difference generator V.
A slab of dielectric material is inserted into the space between the armatures.
By doing the calculation of the derivative of the electrostatic energy with respect...
So my idea was to separate the capacitor into two individual ones, one of length ##l - a## filled with a vacuum and one of length ##a## filled with the glass tube. The capacitances then are
$$
C_0 = \frac{2 \pi \varepsilon_0 (l-a)}{\displaystyle \ln\left( \frac{r_2}{r_1} \right)}
$$
for the...
My attempt would be to calculate the electric fields of the vacuum and dielectric part seperately and then use superpositioning to obtain the full solution. However, I don't see an ##x##-dependency coming along that path. The assignment suggests that there must be one though. Unfortunately, this...
In the given circuit, a transient current will flow and when this current finally stops at equilibrium, the charges ##q_1## and ##q_2## are assumed to deposit at the capacitor plates as shown below. The dashed line indicates an isolated system that will have it's total charge conserved.
If I...
Hi,
I am not sure if I have calculated the task b correctly.
I always interpret an open switch as an infinitely large resistor, which is why no current is flowing through this "resistor". So there is no current in the red circle, as it was the case in task part a, but only in the blue circle...
(a) I think the top plate of C5 could end up with either + or - charge, and not necessarily + charge as shown. This is because the connected plates of C1, C5 and C3 form an isolated system to which we can apply the law of conservation of charge i.e. Total charge just before transient currents...
Question:
Solution first part:
Have I done it right?
I don't know how to begin with second part since the dielectric is non-lineair, and most formulas like $$
D=\epsilon E$$ and $$P= \epsilon_0 \xhi_e E$$, only apply for lineair dielectrics. What to do?
I was thinking about doing KVL around the circuit at the right but I noticed when the switch opens, the current through the circuit at the right is not the same throughout
-5 + Ic*2*1-^3 + Ic*10^3 = -Vc
Ic is not the same around the right circuit so I am stuck....
The end goal is I need to convert a sinusoidal into a square wave using a zero crossing circuit. I have a voltage that ranges from 0 to 400vrms @70kHz from a capacitor that is part of an induction heater tank circuit. My comparator has a peak differential input of +/- 35v so I need to reduce the...
Suppose the switch has been closed for a long time so that the capacitor is fully charged and current is constant.
a)Find the current in each resistor and charge Q of the capacitor.
b)The switch is now opened at t=0s. Write the equation for the current for the resistor of 15kΩ as a function of...
Apparently, we need to integrate the functions from 0 to the time when it is fully charged. However, I integrated in terms of t so the soultion (according to a graph programme) should be around 236 Vs but I don’t see how this could help me.
For the first circuit, Req = ZL + ZC = -j/(w*C) + j*w*L = 0 for short circuit, so w = 0?
For the open circuit case, -j/(w*C) + j*w*L = infinity, so w = infinity?
Is that correct?
we know that flux is equal to the area integral of electric field dotted with dA and we can set this equal to charge enclosed divided by epsilon naught. Thus, in this case, the integral simplifies to E * A = (q_enclosed)/(ε_naught) when we choose a cylindrical gaussian surface with radius of r...
I was wondering why energy of capacitor does not equal change in kinetic energy PLUS change in potential energy where potential energy is the change in the potential energy of the charges. I believe that should be so because energy conservation = change in kinetic energy plus change in potential...
For this part(b) of this problem,
The solution is
However, I tried solving (b) like this:
Since ##Q_{total} = 363 \times 10^{-6} C## then ##Q_1 = 181.5 \times 10^{-6} C ## since the equivalent upper capacitor is in series with the equivalent bottom capacitor so should store the same amount...
a) if I take a Gaussian cylindrical surface whose circular area are present in the meat of the two plates of the capacitor, then the electric flux through this Gaussian surface is zero ( as the electric field inside the meatof the capacitor is zero and between the capacitors, electric field is...
Because of the plate P, the capacitor becomes a piece of conductor. It contains zero net charge and has 0 potential difference. Hence, the capacitance is ## \frac 0 0 # # that is undefined.
The capacitance of a capacitor is defined as its capacity to store charge when a potential difference is...
The the electric field inside decreases due to the presence of a dielectric by a factor of dielectric constant K. Hence the force between the plates will decrease.
Is this right?
What is the difference between a variable capacitor in a AM receiver and a variable capacitor in a FM receiver? I understand that Am is amplitude modulation and that the signal is carried over a changing amplitude and that the frequency is constant. And the opposite in FM signals. And a variable...
Figure:
My attempt at a solution:
Once the capacitors have been applied, we see directly that ##\boxed{v_c=v_0=0\, \textrm{V}}##
Wouldn't this one be done like this?
I know the following: in a circuit with capacitors and coils, if we have
Capacitor: we change for an open circuit.
Coil: we...
My textbook solution states that 1 & 2 are in parallel and so is 3 & 4 and those 2 are in series. That is, (1 P 2) S (3 P 4). My thinking is such: points A & B are of same potential, say V, C & D are of same potential, say x and E & F are are of same potential, say 0. So I can say that 1 and 3...
While going through the catalogues I started to wonder, typically lower ESR caps cost more, but if I need the cap for DC smoothing , to filter out unwanted AC ripple, then I put that cap across my DC rails +-. Now so far so good.
It's ability to filter out the AC ripple will be directly related...
What I have done:
The electromotive force due to Faraday's Law is: ##\mathcal{E}=-\frac{d\phi(\vec{B})}{dt}=\frac{d}{dt}(Ba^2)=a^2\frac{dB}{dt}=-10^{-4}V.##
In the circuit, going around the loop in a clockwise fashion:
##\oint_{\Gamma}\vec{E}\cdot d\vec{l}=-\frac{d\phi(\vec{B})}{dt}\Rightarrow...
So long story short I have a power supply (DIY) for some time and on the secondary side filter/reservoir capacitors there is a small ripple (about 1v PP) of 50khz (the switching frequency of the PSU).
Aside from others methods that I will implement to reduce this I am thinking of adding a shunt...
In MOSCAP, why does the band stop bending as soon as the Si Fermi level touches either the conduction band (inversion) or the valance band (accumulation)?
With reference to picture, l have an oblique slab of material dieletric in a capacitor. The plates of capacitor are infinite and far. How can calculate E and D in dieletric?
I have watched a number of tutorials on how a capacitor works and I'm still confused about a couple things. Suppose we have a battery who's terminals are connected to the battery. It make sense to me that negative electrons accumulate on one side of the dialectric, because they're attracted to...
I understand that the particle will be polarised according to its dielectric constant and the electric field across the capacitor.
However, since it is similar to an insulator and electrons do not move in and out of the particle easily, the particle will not be charged.
How then will...
With a capacitor with a dielectric with the battery on,
##E_{total} = E_0 + E_i##
##\frac{Q_t}{dC_t} = \frac{Q_0}{dC_0} + \frac{Q_i}{dC_i}##
thus,
##\frac{Q_t}{C_t} = \frac{Q_0}{C_0} + \frac{Q_i}{C_i}##
since in a battery ##V_t = V_0, V_i = 0##, so either ##Q_i = 0## or ##C_i = infinite##
but...
The energy stored in a capacitor is derived by integrated the work needed to move charge dQ from one plate to another. I'm confused on how this energy is the same as electrostatic potential energy, the energy needed to assemble this configuration from infinity. In the case of capacitor energy...
Disclaimer: This is not a repost.
The problem wants me to calculate the force of a p.c. , that is isolated by itself (this p.c. is the only charge this problem starts with in this problem) inside a capacitor, a distance h/4 from the bottom plate.
This is what I have though of so far but I...
Before I can find the force on q I must balance the charges. This problem starts of with -q and q inside the capacitor. I have added image charges on the opposite side of each plate. Would this work?
Consider a simple DC circuit containing a 9V battery, a switch, a 10 kΩ resister and a 100 μF capacitor all in series. When the switch is thrown, it will take basically 5 seconds for the capacitor to reach full charge.
Based on what I have read online, the charge on the above capacitor is...
I tried solving the part (a), and got I =1.82 A for the current value using Kirchoff's law.
Next, I want to use Ohm's law to calculate the voltage at point a.
Va = IR
In this equation, will resistance R correspond to 4.4Ω or 8.8Ω?
How do you determine which resistance to use when solving this...
The following is the question and the solution to the question.
I understand the solution to the part where you find the Ceq and derive Qeq from the equation Q = Ceq*V.
However, I do not understand where V1 = V0-V2 come from.
When calculating the minimum voltage, how do you come up with the...
I considered the capacitor as two capacitors in parallel, so the total capacitance is ##C=C_1+C_2=\frac{\varepsilon_0\varepsilon_1 (A/2)}{d}+\frac{\varepsilon_0\varepsilon_2 (A/2)}{d}=\frac{\varepsilon_0 A}{2d}(\varepsilon_1+\varepsilon_2).##
Since the parallel component of the electric field...
I did a kvl loop and got V + 5Io - 15 Io = 0
So, V = 10Io
Then, substituted dq/dt for Io and q/c for V
I get to dq/dt - 50000q = 0
solving this equation i get q = C x e^50000q (c for constant)
my Io = dq/dt
so Io now is 50,000Ce^50000q
now my Q(0) is 3 x 10^-5
So my Io (0) should be...