Capacitors Definition and 884 Threads

Homework Statement Two capacitors (C1 = 9.3 μF and C2 = 29 μF) are connected in parallel across a 12 V battery. a) Find the equivalent capacitance of the two capacitors. Ceq=C1+C2=9.3+29=38.3μF After some time has passed (use for rest of problem): b) How much current flows in this...

I am hoping that general physics is the correct location for this problem, but if I am wrong please say so. I have a problem where two capacitors of different value are in series and are attached to a DC source. Homework Statement Image is a bit blurry but that is how our professor...

Homework Statement Two capacitors, C1 = 4μF and C2 = 9μF, are connected in series with a 30 V battery. The battery is removed and the plates of like sign are connected. Find the initial and final energies for each capacitor. Homework Equations Q=C*V U=q^2/2C Ceq = ∑Ci ( don't know...

If a capacitor is fully charged in a circuit, am I correct in saying that you can ignore that section of the circuit because no current goes through/leaves it?

Homework Statement I've tested the circuit above, when the switch is in the 2nd position (not the one on the picture) and got the below graph from the plotted data I received. The capacitor C1 has been charged to 4V, and will start to discharge through R3. I'll have to explain...

Homework Statement Hello, I am having trouble with a physics lab report I'm working on. I'm going to try and be as clear as possible. Basically, I'm using different values of R and C in determining tau, the time scale in a circuit's behavior. I used a circuit with a resistor and capacitor and...

Homework Statement A parallel plate capacitor with capacitance C is charged to a value q and then isolated. The separation between the plates is then tripled. What was the work required to separate the capacitors?Homework Equations U=1/2CV^2 Q=CV C=ε0A/dThe Attempt at a Solution...

I was watching this video: http://www.youtube.com/watch?v=P8A1U-RZDao&index=7&list=PLLUpvzaZLf3Jv7AjU5pfY8s25-QBCfdIZ and at around 6 minutes, I got confused. Ill summarize it below in case the link does not work: If you have a circuit which consists of a battery which is 12 volts, and a...

When deriving capacity of a parallel plate capacitor, we consider the electric field (sigma/epsilon), i.e. the field due to one of the plates while both the plates are charged with Q and -Q respectively...so should not be the field due to both the plates, i.e. (2sigma/epsilon) since the...

Homework Statement Given the attached circuit, compute Tau, UC1 (t) and UC1 (∞). Then assume t = ∞ and C1 has the potential of Eth. Put the switch in the other position, so that C1 can discharge through R3. C2 will, of course, charge until UC1 = UC2. Compute Tau, UC1(t), UC2(t) and...

capacitors don't require a "dielectric" material they? whenever i hear about capacitors, i hear about the 'dielectric' material, but a dielectric material as opposed to a non-dielectric insulator just means that the material is polarizable. but polarizability only affects the field strength...

I read about an example in which you had two metal plates, and in between them one third of the distance from the top plate downwards (towards the bottom plate) was made up of κ, and the rest was air. THe problem proceeded to calculate the capacitance of them in series. I don't get how the...

Homework Statement Compute V3(t)-V4(t). The capacitors are initially discharged, the voltage source is turned on at t = 0, and the diodes’ forward voltage drop is negligible (Vf = 0). What is the value of V3(10s) – V4(10s)? Vi=4sin(2∏t) RC= 0.1s Homework Equations i (over...

Hello Guys, I am looking for an alternative for the big size electrolytic capacitors. Can you suggest me any alternatives or solutions. I need a small solution with dimensions of 2.2μ, and 440 volt. Thanks in Advance,

1-If we had a spherical capacitor and the voltage across it is 1000 V, I need to know the charge on every plate, I know 2 ways to solve this either using C=Q/V or V=Q/r * 1/4ε0∏. So, which one should I use, and why? 2-Another thing, according to hyperphysics the formula for the capacitance of...

For the circuit posted (or any similar circuits really), how do we simplify to determine the equivalent capacitance, voltage and charge of the system? With multiple batteries, how does this affect the circuit? Sorry for not posting in the homework section. It's just that I don't really need an...

Capacitance -- combining multiple capacitors for equivalent C In the given problem, Ceq = C1C2C3C4/(C1 + C2 + C3 + C4) The answer says the equivalent capacitance is always less than C1 but I can't come up with thy. When I do this, I can't seem to prove that equivalent capacitance is always...

Homework Statement Find Vy(t) in terms of t, where Is=10uA, C1=4000pF, C2=1000pF _Vx_____||___ Vy_||____ | C1 C2 | | | | | Is Up | | | |...

Homework Statement For the capacitor network shown in Fig. P24.55, the potential difference across ab is 12.0V. Find (a) the total energy stored in this network and (b) the energy stored in the 4.80-μF capacitor. Homework Equations C= Q/V U= Q2/2C = .5CV2 = .5QV Capacitors in Series: 1/Ceq =...

Homework Statement Three capacitors of 2μF, 3μF and 5μF are independently charged with batteries of emf's 5V, 20V and 10V respectively. After disconnecting from voltage sources, these capacitors are connected as shown in figure with their positive polarity connected to A and negative polarity...

Capacitors , why can't series combination be used in an open circuit?? they say we cannot apply series combination formula for the capacitors in an open circuit,,,but why?? why can't we find the equivalent capacitance in an open circuit?

Homework Statement Two capacitors A and B with capacitance 3 μF and 2 μF are charged to potential difference of 100 V and 180 V respectively. These two capacitors are connected to an uncharged capacitor of 2 μF using a switch as shown in the diagram. Determine the final charge on each...

Hello, My friend was reading up on transistors and basically the way i see it, a transistor is a device which (using little current/voltage , depending on the transistor) can control larger amounts of current/voltage , so all transistors are devices which work by letting current flow through...

A parallel plate capacitor of circular cross section r>>d, and separation d. It is charged to potential V then disconnected from the circuit . What will be the work done in moving the capacitor from d to d1? Answer: Here the initial energy is 1/2CV^{2} Where C=Aε/d While moving the capacitor...

Homework Statement Homework Equations Q=CThe Attempt at a Solution a) I want to say that since both have the same potentials then it is similar to a parallel circuit where the charges can differ on each capacitor. If i think of point A as an input and point B as an output then the potential...

I found this problem in the book and the exact problem is not important, but I don't understand the picture. Book claims that after voltage source is disconnected and switch closed these capacitors in picture are parallel although I tend to think they are in series. (I agree they are in parallel...

Hi I'm wondering why does the charge resides on the plates on a capacitor when it's charged but not on say two closely placed wires or circuit traces etc, well I do understand that charges stay on capacitor plates because the opposite charges tend to attract and with a distance between them they...

Question: Considering a parallel-plate capacitor that has a slab of dielectric with relative permittivity epsilomd = 5 and thickness d = 2 mm occupies half of the gap. The half is air with relative permittivity epsilom2=1 Denoting the electric field, and electric displacement in the...

Is adding a coupling capacitor to the generator necessary when injecting a signal for troubleshooting.

Hello, I have an issue with the problem below. I have a series connection of two variable capacitances C_{1}(t) and C_{2}(t). I want to establish the differential equation between the current i and voltage V on the ports of the series connection. The capacitance of the series connection of...

Hello, I'm studying capacitors in my freshman physics class and I'm not quite following my book here. My book states that we can calculate the potential energy U stored within a capacitor by calculating the work done to charge it. Let q and v be the charge and the potential difference...

Homework Statement So 4 capacitors are hooked up as shown in the picture on the left http://i.imgur.com/RiNcYz4.png each with C=0.8 F and the voltage from the battery V=16.6 V Then they are disconnected and hooked up as shown on the left with one capacitor flipped. What is the effective...

Homework Statement Two square metal plates with sides of length 0.1 m are separated in vacuum by 10-3 m. Find their capacitance. Homework Equations C = Q/V For a parallel plate capacitor: C = E0A/L The Attempt at a Solution If A is supposed to be the length of the metal...

Homework Statement an electromagnet is operated at 50A. assuming an inductance of 100H for the magnet's coil, what voltage will be developed when the switch is opened? when it is closed? assume that the switch requires 1 millisecond to operate. Homework Equations I(t) =...

What is fundamental physical constraint which doesn't allow the best (super)capacitors rival the best batteries in energy density? Or it could change someday?

usually when we have some initial variable U(0), and we have some factor K that changes this initial variable, we usually express the new variable U(f) like so.. U(f)=KU(0) and NOT the other way around... so why is the dielectric constant expressed in the following way? Eκ=E0 this...

Homework Statement Conceptually, why is the equivalent charge of a circuit with capacitors in series equal to the charge on one capacitor? For example, the lecture says Q_eq = Q1 = Q2 = Q3 =... for multiple capacitors in series. Why isn't the equivalent charge the sum of all the charges on...

In general, by what considerations guide the decision to size a capactior to smooth voltage signals? For example, if I were to use a 3.3V regulator in a circuit design, what size cap should be set in place to ensure a smooth regulated voltage? My attempt at answering my own question would bet...

1. At time t = 0, a 23 ohms resistor is linked to a 4.4V battery. How much charge has gone through the resistor after 5 seconds? 2. Q = CΔV ΔV = IR 3. ΔV = IR I = ΔV/R = 4.4/24 A. I'm not sure what to do next.

Please help me with this "capacitors" problem ? Two capacitors connected in Parallel and their sum(Ceq12) is connected in series with a third capacitor . Givens are : (( C1 = unknown value (X) , C2 = 4uF , C3 = 18 uF , Q1 = 300 uC , V = 90V )) The question wants the value of C1 , ( I find it...

Homework Statement Three capacitors having capacitance C1 = 3.00 microF, C2 = 8.50 microF and C3 = 15.0 microF are connected to a 24.0 V battery as shown. Calculate the charge on C3. Homework Equations $$ C_{eq}= \left ( \frac{1}{C_1+C_2} + \frac{1}{C_3}\right )^{-1}$$ Q = CΔV The...

I have seen power rails bypassed with parallel capacitors which are at least an order of magnitude apart in capacitance value. From what I understand, one capacitor filters high frequency noise and the other filters low frequency noise. 1. Which capacitor does what? The low value capacitor...

Homework Statement Given that the diodes are ideal for the circuits a) and b), plot each of their output for the input shown. Label the most positive and most negative levels. Assume CR >> THomework Equations The Attempt at a Solution I am having a really hard time understanding the role of...

My daughter's TV won't turn on. Seems like the power panel. I'm not much of an electronics person but after looking around the net it seems capacitors are often to blame. Everything I've seen though shows a bulge in the capacitor with the potential of there being some loss of fluid inside that...

Homework Statement I am trying to determine the charge on C2 which is a 3 μF cap in parallel with a 2 μF cap that are both in series with a 4 μF capacitor. The voltage source is 12V (diagram attached) Homework Equations Q=CV 1/Ceq= (1/C1)+(1/C23) The Attempt at a Solution...

Homework Statement See the image : http://postimg.org/image/hswmylvz1/ In the image, potential of point a is Va and that of point b is Vb. We have to find out Va-Vb for the circuit as shown in the image.Homework Equations ----- The Attempt at a Solution Let the potential of negative...

Homework Statement Hi all, My question is: In what kind of device the enclosed schematic can find an application? The bipolar switch has two positions U and u- which are for upper position and D and d- which are for down position. The main question is on what kind of equation the voltage...

Homework Statement 6. Based on what you can tell so far, if you have an N number of capacitors (say at a nuclear fission site) and you need massive power storage, you would place the N number of capacitors in a. Series b. Parallel c. Combination of series and parallel d. Both choices a and b...

To capacitors are charged up with a potential difference of 24 volts, and then connected in series in a closed circuit. What is the final charge on each capacitor? C1 = 2,0*10^-6 F and C2 = 6,0*10^-6 F What I did was to compute the total capacitance of the system, and use that to figure out...

Homework Statement A capacitor is initially connected to a voltage source in series for a long time. At time t0 the make before break switch switches to another series circuit which includes the capacitor. This means that the capacitor will have an initial voltage v(0-) = voltage source...