Capacitance Definition and 874 Threads

What factors determine the anode plate-to-grid capacitance? I know that the capacitance of a regular capacitor is determined by the surface area of the plates and is inversely proportional to the distance between them. Does this hold for vacuum tube grids and anode plates? The reason I'm asking...

Does current pass when parallel plate capacitors are introduced in circuit?

Anybody please help to tell me if there's a book or journal that clearly describe the definition and differences ( best if it comes with illustration or diagram) between these engineering terms: (1)partial capacitance (2)mutual capacitance (3)self capacitance (4)earth capacitance Thank you!

I am working on a system that uses capacitance sensor probes, the system components are the probe, triaxial cable with LEMO connectors, BNC cable, oscillator, and a demodulator. I have had some trouble finding ways to troubleshoot the system other then basically testing continuity. Are there any...

Homework Statement 1. Referring to the picture, switch S1 is closed at t=0. a) What is the current in the circuit loop at t=0 and t=∞? b) What is the voltage on C at t=0 and t=∞? (4M) (Picture's Link: http://s29.postimg.org/bfsbw2hc5/physexam1q7.png) Homework Equations When charging, 1.) ε -...

Hi folks, I'm playing around with capacitive sensors (mutual capacitance sensors) and interested in computing/approximating the capacitance between the sensor lines. Mutual capacitance sensors usually consist of two lines/conductors that intersect. Obviously, one can model this is a parallel...

Homework Statement After a capacitor of capacitance ##C_1## is charged up to a voltage ##V_o##, the Battery is removed from the circuit. Another capacitor of capacitance ##C_2## is connected in series with the capaciotr ##C_1##. Find the charge on each capacitor after equilibrium is attained...

Hi, I am interested to simulate the capacitor with plates having an angle of 195 degrees between them. https://dl.dropboxusercontent.com/u/32847378/cp1.jpg I know that if the angle between of plates is 180 deg, then electric lines of forces will follow a elliptical path and equipotential...

Hello, I am new to electronics and am having trouble understanding this formula for capacitance: Could someone please break this down into layman terms? Interestingly π appears? I'd like to understand why that exists in capacitance. Thank you all in advance!

Let us take a charged capacitor and move the plates such that it the distance between them be constant. For example, one moves towards left and other moves upwards. Assuming only overlapping area affects capacitance... WILL THE CHARGE STORED IN CAPACITOR CHANGE? I know the capacitance changes.

Hi, I'm looking at an experiment at the moment whereby I'm using an LCR meter to measure capacitance. However the effect of leads seems to be quite profound. Connecting up 50cm leads in a parallel setup has a capacitance of about 3pF and in a circle setup about 26pF. What causes such a...

I have some experimental circuit element that exhibits both resistance and capacitance, and results in nonlinear I-V curves. can i extract capacitance and resistance of this element just from the I-V curve? or do I need time-axis data? a suggestion on what equation to use to fit this data? thanks.

My question is why is the energy stored in a capacitance equals to half the energy supplied by the battery. I already know that there is heat loss in wires. But what I really want to know is that why is it only half of it ? It could have been any other fraction.

I've gotten myself in a bit of a muddle here, I'm hoping you lovelies can help me out! So, the capacitance relates to the amount of charge a capacitor can store. Higher capacitance, greater charge. Greater stored charge, greater stored energy (right? or not?). So a higher capacitance means you...

Im trying to gain a more conceptual understanding of capacitance. Capacitance is the ability of a parallel plate capacitor to store charge, and thereby voltage, between its two plates. The more charge the capacitor can store per input voltage, the greater the capacitance. Hence the...

Hi everyone, I'm new in physics forum and this is my first post. So basically, our lecturer grouped us and gave each group a project to carry out. And the only information that we got is the name ( The one we got is "Model of the capacitance and dielectric" ). With only this information, me...

im hooking up 6 450v 10000uf capacitors in parallel for an exparement for school (under supervision of my professor) he won't tell me how to monitor these devices and how to know when they are full and when to release them. does anyone think they could give me a quick and dirty answer?

Homework Statement Calculate the number of sodium ions entering a non-myelinated axon during the action potential, per metre of axon length. The change in potential is 100 mV, the axon membrane capacitance per unit length is 3 × 10−7 F/m, and the charge on an ion is 1.6 × 10−19 C. What...

Homework Statement In the circuit shown in the figure the voltage of the battery is 15.0 V, and the capacitors have the following capacitances: C1 = 2.32 mF, C2 = 2.25 mF, C3 = 4.85 mF, C4 = 4.89 mF What is the equivalent capacitance of the four capacitors? http://tinypic.com/r/24dn5oi/8 Two...

Hi there, I have a system that trace every 10ms the voltage of the dc link and in parallel there are capacitors on the DC Link that is about 100 F. The DC Link Voltage can raise as high as 300VDC and it fluctuates. (I am just throwing out numbers as I'm just trying to grasp the concepts) To...

Hello, Suppose we have an electric circuit consists of a battery and 2 wires connected to both ends of the battery. When the two wires are not connected together (open circuit) do the surface charges of both conductors accumulate? if yes, can we say at the end of both wires separated by the...

Hello guys, I read some articles recently about how touchscreens work by using the capacitance in human bodies. I'v seen the human body capacitance is quoted at around 100pf, is it the same when the human body is floating in mid-air, as if it is standing on the ground? My goal is to detect...

Homework Statement the effective capacitance across AB of the infinite ladder shown in the figure The Attempt at a Solution

I am trying to get an estimation the junction capacitance of my GaAs Photodiode with respect to varying bias voltages. My Semiconductor Physics online textbook gives the following equations with ε0 = permittivity of free space εGgAs = GaAs dielectric constant μ = Mobility of...

We know that the main use of capacitor is to store charge in the form of electric field,and we want it to store as much charge as possible without leaking and we try to decrease the potential difference between the conductors.But if we increase the charge of the conductor it will consequently...

Hi guys, I hope this is the correct section otherwise I apologize :).The goal is to find the capacity of a non linear capacitance composed by an upper plate which has a cup shape and the lower plate which is flat. The problem is the following: by means of a FEM simulation of the Poisson...

Why capacitance behaves as shortcircuited in uncharged state and why as open circuited when its fully charged..?? I am reallt doubtful..:confused: i=Cdv/dt...so if we r appyling a dc voltage ..in that case i should be zero.>! thn why short-circuited..??

Hi everybody, I'm new at the forum. I've started learning physics on my school last year. I've a question. How can we measure the voltage stated on the definition of capacitance? Just V=Q/C ? Or how to measure the capacitance? What's about voltage? I didn't know that Q=C.V. What is...

I know the capacitance of cylindrical shell formula if both cylinder length is same.If cylinders length differs between which the dielctric is sandwitched what is the formula to calculte the capacitance?

Question: A stationary electron is a point of charge. What is the energy density of U, it's electric field at a radial distance r=1mm? Know: 1mm=1*10^-3m u=(1/2)(epsilon naught)(E^2) E=kq/r^2 I know I have to end up solving for (E)^2, where E=kq/r^2, but how do I determine what charge to use...

Homework Statement In the above circuit, find the potential difference across AB. 2. Solution Online "C34 = 4μf C2,34 = 12μf CEQ = 4.8μf q = CEQ x V the q on 1 is 48μC, thus V1 = q/c V1 = 6v VPQ = 10 - 6 = 4v By Symmetry of 3 and 4 , VAB = 2v" 3.My question...

Hi all, I have been looking at this problem for a while now and can not seem to be able to reach the correct answer, hopefully someone out there can help me! A capacitor of capacitance 180pF is charged to a P.D of 12V and then discharged through a sensitive meter. This sequence of...

Why does a voltage tester (that looks like a screwdriver) turn on even when you are "heavily" insulated from the ground e.g. sitting on a wooden chair. Is it the result of capacitance between the human body and the ground? (i.e. the body and the ground act as conductors, whereas the insulated...

Homework Statement Calculate the equivalent capacitance between points a and b in the figure below (C1 = 4.10 μC and C2 = 1.60 μC). Notice that this system is not a simple series or parallel combination. Homework Equations Series: CT = [1/c1 + 1/c2...]-1 Parallel: CT = C1 + C2... The...

I need guidance calculating the capacitance between two infinitely parallel long wires that are parallel to a large flat metal sheet. Condition: V = 0 at the origin. Both plane and lines have uniform charge. Left line: Negative charge density Right Line: Positive charge density...

Hi there, I'm doing a home study course including a section on dynamic fields and waves. I am trying to understand how to find capacitance using initial charge, inductance and energy. From a previous section, I know I can find the maximum current using Um=1/2 LI2 However, I can't see...

Hi everyone. I am trying to determine the capacitance between two adjacent coils. Each coil is identical, made of 20 awg wire consisting of 10 layers of 20 turns each, spaced about 1 inch apart and wound on a 1 1/2 inch diameter coil former. How would I go about finding/calculating...

Homework Statement Reduce the circuit below into a single equivalent capacitor at terminals a,b. Assume all initial voltages at t = 0 are zero. Homework Equations The Attempt at a Solution Okay, this is the circuit I had in mind when I made this thread earlier...

A first capacitor is initially connected to potential source ?. The charged capacitor is then removed from the source and connected to a second initially uncharged capacitor. Determine the final potential across the first capacitor long after the switch is closed. Homework Statement...

Answer true/false to the following statements about parallel-plate capacitors. 1) The charges on the two plates of a capacitor are equal. 2) Capacitance is the property of a device that enables it to store current. 3) The capacitance of a parallel-plate capacitor is proportional to the...

[b]1.Question: A charged capacitor is connected across an 8.0 kΩ resistor and allowed to discharge. The capacitor loses 63.2% of it's original charge in a time of 6.2 seconds. Calculate the capacitance of the capacitor. (This is everything they give and nothing extra, I have checked and made...

A circuit uses a neon lamp. The neon lamp has a threshold voltage V0 for conduction, because no current flows until the neon gas in the tube is ionized by a sufficiently strong electric field. Once the threshold voltage is exceeded, the lamp has negligible resistance. The capacitor stores...

Hi guys, I'm trying to obtain the CxV curve from moscap in SPICE (hspice). Note that I'm not talking about the sum of the capacitances from the mos transistor, but the transistor behaving as a capacitor. Is there an easy way to do this?

Hello, my timetabled experiments for lab work are a week or two ahead of my E&M course which means I'm doing the experiments before being introduced to the theory. As part of my prep work I need to come up with an expression for the total capacitance of a number of different circuits involving...

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...

[FONT="Book Antiqua"]As everybody already knows, voltage is defined as the work done/energy per unit charge. I see voltage as being the idea of giving the charge carriers a 'want' to move: when a closed circuit is attached to a battery, the voltage makes the charges want to move, and they can...

There was a thread a while ago regarding a capacitor where the capacitance was changed while it was part of a circuit. I won't link the thread here as it was kind of a train wreck... Now the explanation given was that in order to change the capacitance work would have to be done to cause...

Hi, In Spice, the capacitance between two points x, y is defined as follows: Cxy = - dQx / dVy for x != y Cxx = dQx/dVx Could anyone help me explain why it is defined like that? I know that C = dQ/dV but the formula above seems strange to me. Is my understanding below correct? Cxy =...

I have done no. 1, but I don't how to do no. 2. Someone, please help. Power source voltage e(t) = sqrt(2)*20sin2t [V], current i(t) = 5sin(2t - pi/4) [A]. 1. Find the values of resistance R, and inductance L. 2. Let V be the phasor of voltage v(t). Find the capacitance value of the...

Hello all! My friend and I are having a bit of a discussion. We did an experiment on liquid crystals as dielectrics with changing voltage, and we came across some weird conclusions (capacitance decreased with increasing voltage? odd. Our theory is that liquid crystals don't act as normal...