Capacitance Definition and 874 Threads

A sheet of gold foil (negligible thickness) is placed between the plates of a capacitor and has the same area as each of the plates. The foil is parallel to the plates, at a position 1/2 of the way from one to the other. Before the foil is inserted, the capacitance is 7.9μF. What is the...

Problem: When a dielectric slab is inserted between the plates of one of the two identical capacitors in Fig. 25-23, do the following properties of that capacitor increase, decrease, or remain the same: (a) capacitance, (b) charge, (c) potential difference (d) How about the same properties of...

Homework Statement In the figure C1 = 10.0 μF,C2 = 20.0 μF and C3 = 27.0 μF. If no capacitor can withstand a potential difference of more than 130 V without failure, what is (a) the magnitude of the maximum potential difference that can exist between points A and B and (b) the maximum energy...

Homework Statement I'm trying to find the capacitance of a system of 3 concentric hollow cylinders. The first cylinder has radius R, the second radius 2R, the third radius 3R. Cylinders 1 and 3 are connected by a wire. In total, they have charge +λ, and the second cylinder has charge -λ. The...

Homework Statement When a dielectric is partially inserted between two plates of a capacitor that is disconnected, what will be it's motion? Also what will be its motion if the capacitor is connected to a battery? Homework EquationsThe Attempt at a Solution For the first part. I think the...

Homework Statement 1) Two solid conducting spheres have radius r1 = 3 cm and r2 = 42 cm. The two spheres are connected by a thin conducting wire. Assume: - the wire is very long and thin, with negligible surface area, so it does not affect the capacitance of the system. - the switch is...

Why does the method of images work?

Homework Statement Coaxial cable has double layered dielectric. a=2mm, b=4mm, c=8mm, εr1=3, εr2=4.5, Uab=1000V 1. Calculate capacitance per unit length of a cable. 2. Calculate inner and outer charge densities of a cable. 2. Homework Equations Gauss law C'=Q'/U σ = nD σp = nP 3. The Attempt...

Homework Statement Two cylindrical conductors, of distance between them d and radius a (a<<d), have dielectric layer of relative permitivitty εr and thickness a. Calculate capacitance per unit length of this system. Homework Equations Capacitance per unit length, C'=Q'/U Gauss law, cylindrical...

Edit: sorry i realized i posted this in the wrong section. Can some move it to hw? Thank you. Hey i was s[SIZE=16px]tudying intro E&M recently and i started learning about RC circuits. Up until this point everything, concept wise, has made sense for me. Then I learned how RC circuits work, and...

Homework Statement Two conductive metal plates are bonded together. Upon bonding, an oxide layer forms between them. The oxide layer is negligible thus the overall resistance of the plates is small. However I am having trouble finding this overall resistance, i.e., trying to find Cp and Rp...

I posted this picture in another thread but I now have a specific question for the capactance measurement between both transducers (the middle C). How can I measure the capacitance of this using an LCR meter. Where should the leads be put and what are some averages of a capacitance I should be...

The question is the following: a) Determine all load voltages and currents b) Determine the resistance reflected into the primary. Answer a) R(l): 35V, 2.91A, X(cl): 15V, 1.5 A The answer to part (b) is apparently 34.5 Ohms. How did they arrive at these answers? I am not sure...

I am making a sonoluminescence experiment and part of it is two transducers touching a glass beaker with water. However, I don't know exactly how to measure the capacitance. With the picture attached, the places marked in green with "C?" written on them are where I was told there would be...

Homework Statement Please see attached. Homework EquationsThe Attempt at a Solution I get a result of ## \alpha =\frac{1}{2} ## for part a) - which I think is correct. I'm stuck however on part b) - with the dielectrics. I have that the field in the region where the dielectric is ##E_{1}##...

Homework Statement Why are both these problems identical? In both cases, c>b>a. Q1 Three concentric conducting shells A, B and C of radii a, b and c are arranged as shown. A dielectric of dielectric constant K is filled between A and B. Find the capacitance between A and C. Q2 A spherical...

Hi, I would like to know how to calculate capacitance between two wires which are parallel but not necessarily straight.for instance the two wires might be parabolic..I would like to calculate for such general structures.i.e) two parallel wires that are not necessarily straight. Thanks in advance

Hi, I would like to know how to calculate capacitance between two wires which are parallel but not necessarily straight.for instance the two wires might be parabolic..I would like to calculate for such general structures.i.e) two parallel wires that are not necessarily straight. Thanks in...

Homework Statement Find the potential difference Va-Vb between points a and b. Homework EquationsThe Attempt at a Solution Each capacitors left plate will have difference amount of positive charge and right plate will have negative charge. After that i don't know how to proceed.

Homework Statement A capacitor is charged to V = 5 kV. A wire is then connected to one plate and is slowly connected to the other. Before actually touching the plate, a spark of length l = 1 cm shoots from the wire to the plate. Using this information, estimate the dielectric breakdown of air...

I was wondering if there is any way to electrically charge photons?

Homework Statement Find capacitance across AB So i divided the current into q1 and q2 as shown. then i assumed that q₂>q₁. Homework Equations ##C=\frac{Q}{V}## I don't know anything after KVL KCL and loop law. The Attempt at a Solution So i split the current at T into q₃ and q₂-q₃ by the...

i have done the capacitance of an isolated charged sphere (=4 pi E R).but can we find capacitance of an isolated ,infinite charged plate too??how?

So it says here that a conducting sphere of radius R with a charge Q uniformly distributed over its surface has V = Q/4πεR , using infinity as the reference point having zero potential,,V (∞) = 0. This gives C = Q/|ΔV| = Q/(Q/4πεR)=4πεR. Does ,V (∞) mean that you are taking the potential of a...

Homework Statement Four metallic plates each of surface area S are placed at some distance from each other as shown in figure. Then capacitance of the system between P and Q is A. ## \frac{ε_0S}{3d} ## B. ## \frac{ε_0S}{2d} ## C. ## \frac{3ε_0S}{2d} ## D. ## \frac{3ε_0S}{d} ## Homework...

Homework Statement Four identical parallel metal plates with area $$S$$ and distance between each two $$d$$ are located in air. The external plates are connected by wire. What is the equivalent capacitance between A and B? This is problem from Irodov.Homework Equations $$q=UC$$[/B]The Attempt...

1-capacitance of sphere with radius r : 4πεr 2-capacitance of 2 concentric spheres with inner radius a and outer radius b : 4πε(a.b/b-a) 3-when the outer the outer sphere is earthed it gives the same capacitance as in number 2 4-when the inner sphere is earthed it gives the sum of capacitances...

Homework Statement Well its 2 questions: Immersing a pair of gold electrodes in a saline solution in the presence of a fixed voltage causes the capacitance to: IncreaseDecreaseRemain unalteredIncrease briefly and then return to its original value Immersing a pair of gold electrodes in a...

V' changes over time. How can I determine the influence from parasitic capacitance (~50 pF) on V? R wire ~ 100 ohm. If I need to read data (V' can change rapidly) from this at 50hz, does it influence reading accuracy? How can I determine values from which I need to be careful when reading data...

Homework Statement Two long wires with the same cross section are arranged in air PARALLEL to each other . Assume both have opposite charge densities +λ and -λ. The distance between the axis of the wire is η times larger than the radius(r) of wires cross section . What would be the capacitance...

Homework Statement A 197-pF capacitor is connected in series with an unknown capacitor, and as a series combination they are connected to a 25.4-V battery. If the 197-pF capacitor stores 143 pC of charge on its plates, what is the unknown capacitance? Homework Equations Q = C*V (charge stored...

Homework Statement Three conducting plates, each of area A = 3.5 cm2, are connected in such a way that the center plate can be moved between the two fixed outer plates. If the distances between the outer plates and the center plate are d1 = 0.35 mm and d2 = 0.65 mm, find the effective...

Homework Statement Capacitors C1 and C2 are connected in series and this combination is connected in parallel with capacitor C3. Homework Equations Q=CV Ceq=C1+C2+C3 equivalent capacitance for capacitors in parallel 1/Ceq=1/C1+1/C2+1/C3 equivalent capacitance for capacitors in series The...

Hello, I have had a question on my mind that a generic google search has so far been unable to answer for me. I know that marx generators multiple voltage by cascading capacitor discharges so that you get a final voltage of n x Vinit - where n is number of capacitors and Vinit is your initial...

Odd question, would anybody know what would happen if a parallel plate capacitor (good conductor) had a soft magnetic material (fairly poor conductor) as a dielectric? What would be the DC/AC electrical characteristics of this?

Homework Statement The plates of a spherical capacitor have radii 51.8 mm and 55.0 mm. (a) Calculate the capacitance. (b) What must be the plate area of a parallel-plate capacitor with the same plate separation and capacitance? (givens) a = 51.8 mm b = 55.0 mm d = 3.2 mm ε0 = 8.85E-12...

My question is : What is the absolute capacitance?In my electricity lab, I was assigned to prepare a report on measuring absolute capacitance of a capacitor using ballistic galvanometer. I am familiar to the term self capacitance but not the absolute one. My mentor asked me to find it out by...

Homework Statement Dry air has a resistivity of about 3*10^13 Ωm. A capacitor has square plates 10cm on a side separated by 1.2mm of dry air. The capacitor is charged to 250V. Assuming the potential difference does not change as the charge flows, what fraction of the charge will flow across the...

Homework Statement When an initially charged capacitor is connected in a circuit with an uncharged capacitor, why would the total energy of both capacitors be less than the initial energy of the charged capacitor? Homework Equations This was a question asking for an explanation, so I'm not...

Hi all, My friend and I have created a homemade supercapacitor. It can power a LED light and small alarm clock. We charged it up to 1.5 Volts. I was wondering if anyone knew how to find the exact capacitance in Farads, any help will be appreciated. I have added the steps that we have taken in...

Hi there, new to this website so please bare with me if I break any rules and let me know for future. I am a maths and physics tutor but occasionally I come across a question I just cannot work the answer for. In this case I know the answer but I can't get to it. 1. Homework Statement...

I don't know if this is the right way of describing it, but I need to activate an area of capacitance on a touchscreen by applying some current to a piece of conducting material like tinfoil. I am needing to remotely turn pages on a touchscreen ereading device with a microcontroller, and this...

http://<a href="http://imgur.com/UwulXqg"><img src="http://i.imgur.com/UwulXqg.png" title="source: imgur.com" /></a>[/PLAIN] 1. Homework Statement Find equivalent capacitance of this formation from a to b, C1=4.1 uF, C2=6.86 uF, C3=5.03 uF, C4=5.92 uF http://imgur.com/UwulXqg Homework...

I've been looking all over and to my great surprise have not be able to find an answer to this question. What is the capacitance between to parallel plates if one plate is larger than the other? For example, the capacitance between a 1" diameter plate and a 4" diameter plate. Thanks.

If there is a parallel plate capacitor with plate area, A, plate separation, d, and a slab of copper of thickness, b, is inserted exactly halfway between the plates. How to find it's new capacitance, C', and new potential difference, V' ? Answer: V' = E(d-b) and C' = εA / (d-b) I...

In the figure given the capacitance for the two pair would be same. Can anybody please explain me how the charge would be distributed across each plate? I think that the middle plate being isolated should have +Q on one side and -Q on other, but how would be the charge distribution about the...

Homework Statement Find the pd accros C2 Homework Equations Q=CV The Attempt at a Solution i find C23 = (C2C3)/ (C2 + C3) then find Q23 = V x C23 Q23 = Q2 = C2V2 => V2 i used this and got V2 = 15V , however the answer is 20V , and i even didnt use the data of C1 . am i wrong somewhere ?

Hello everyone, I'm an engineer, and though I highly doubt I'd use this in my mechanic courses...I do truly want to understand what it is I'm putting into application here: So I'm going to explain my understanding of capacitance, be prepared for an extensive reading. I'm doing this because I...

Lenz law states the induced emf in any circuit is always in a direction to oppose the effect that produced it. So my question is, 1. Does this mean xl creates a difference in potential and actual electrons flowing in the opposite direction or just oppose the current direction that created it...

Homework Statement Imagine that you have a light-bulb that has a resistance of about 10 ohms and that can tolerate a maximum voltage of 3 volts. Imagine that you want to connect this to a charged capacitor large enough to keep the bulb glowing reasonably brightly for more than 10 seconds...