Capacitance Definition and 874 Threads

1. The Question a. What is the equivalent capacitance of the combination shown in the figure ? b. If a 100V battery is connected across the combination, what is the charge on each capacitor? c. What is the voltage across each? 2. Equations C=Q/V, adding capacitance rules 3...

1. Homework Statement , from my crappy textbook 2. Homework Equations barely explained in my crappy textbook Q=CV C=\epsilon A/d 3. The Attempt at a Solution that should be easy but the textbook is crap Before squeezing: Simplify the circuit by combining the two capacitors in...

Homework Statement Two metal objects have net charges of +70pC and -70pC, which result in a 20V potential difference between them. a.) What is the capacitance of the system? b.)If the charges are changed to +200pC and -200pC, what does the capacitance become? Homework Equations...

Homework Statement We're supposed to find the capacitance of a system of two conducting spheres, one of radius r_1 and charge Q, the other of radius r_2 and charge -Q, separated by a distance L (this is the distance between their centers) that's very large compared to either r_1 or r_2.Homework...

Homework Statement Given the following: • a battery, • a digital voltmeter (which records voltage as a function of time), • a digital ammeter (which records current as a function of time), • a battered industrial capacitor, • two copper plates, • and several bits of copper wire...

Homework Statement Hello I am studyin for a test and I just wanted to make sure I understand this basic idea... All C's are 5 micro F All L's=2H Homework Equations The Attempt at a Solution For the I came to the conclusion that Ceq=5 micro F the ones circled in blue...

Homework Statement A cell membrane is composed of lipid molecules and approximately 10.29 nm thick. If the dielectric constant of the lipid is kappa= 5 , what is the approximate capacitance of a spherical cell that has a diameter of 10.29 micro meters? Homework Equations E=KQ/r^2...

[b]1. A 2.05 µF capacitor (#1) is charged to 901 V and a 6.68 µF capacitor (#2) is charged to 671 V. These capacitors are then disconnected from their batteries. Next the positive plates are connected to each other and the negative plates are connected to each other. What will be the potential...

I want to know if I am figuring correctly. I am putting together a 12 volt 3 amp DC power supply. The formula in the instructions is C = Tc / R. I figured the required cap to be 20,750 uf. When I went to a couple of supply catalogs to check the price for the cap I found that no one had had a...

Dear Readers, I am trying to build a Schering bridge to measure capacitance change for my research. I need to reduce the cable (line) capacitance to a minimum. I am using an ac 4V (rms), 250 KHz supply. I tried to use two separate coaxial cables to connect the capacitor plates. The signal...

Problem 1 Two parallel metal plates are connected to a voltage source so that their potential difference is maintained at 350 V. The two plates are separated by 1.00 cm. An electron is released from rest at the negative plate and accelerates toward the positive plate. (a) Determine the...

What exactly is capacitance? "Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential" according to wikipedia.com However, following C=\frac{Q}{V} i cannot get the fact that the smaller the voltage between a capacitor, the bigger its...

Homework Statement THREE CAPACITORS HAVING CAPACITANCE 8.4 F, 8.4 F, 4.2 F ARE CONNECTED IN SERIES ACROSS A 36 V POTENTIAL DIFFERENCE. THE CAPACITORS ARE DISCONNECTED FROM THE POTENTIAL DIFFERENCE WITHOUT ALLOWING THEM TO DISCHARGE. THEY ARE THEN RECONNECTED IN PARALLEL WITH EACH OTHER...

Okay so the question is 15. (a) Calculate the electric capacitance of the Earth. (b) Positively charged cosmic ray particles are known to arrive at Earth at the rate of approximately 1 particle per square centimetre per second. If each particle is assumed to be singly charged...

Is there a proof that states that if a system only contains perfect conductors, dielectrics and voltage sources that the capacitance between any two conductors is only geometry dependent?

Homework Statement Find the Equivalent Capacitance: Homework Equations c=Q/V Conservation of energy The Attempt at a Solution I made Q1 be the capacitor of 1uf, the top 2uf be the capacitor of Q2, bottom capacitor of 2uf be Q'2, capacitor of 4uf be Q4, capacitor of 5uf be Q5...

Homework Statement Find the equivalent capacitance of the picture in the attachment file Homework Equations The Attempt at a Solution The circuit is neither in parallel or series. I tried breaking it up into series and parallel but it seem too easy to be correct. Any tips on solving this?

Hi all, Is there any relation between the membrane capacitance and the Nernst potential? Refs: membrance capacitance http://www.cnbc.cmu.edu/~bard/passive2/node5.html Nernst potential http://en.wikipedia.org/wiki/Nernst_equation#Nernst_potential

Determine (a) capacitance and (b) the difference in the maximum potential that can be applied to a parallel plate capacitor filled with Teflon (k=2,1), whose area the plate is 1,75 cm^2 and the separation between the plates is 40x10^{-6}m. My solution (a) C. = ( E. * A )/d =...

As a person moves in an environment dry, electric charge accumulates in the body. Since the body is in high voltage, positive or negative, can download by visible sparks or shocks. Consider a human body and separate the soil, with typical capacitance of 150pF. (a) Load that the body produces...

Homework Statement A capacitor is constructed of interlocking plates as shown in the figure (a cross-sectional view). The separation between adjacent plates is 1.26 mm, and the effective area of one of the adjacent plates is 6.1 cm2...

Homework Statement The flash unit in a camera uses a special circuit to “step up” the V = 3.1 V from the batteries to V' = 300 V, which charges a capacitor The capacitor is then discharged through a flashlamp. The discharge takes t = 12 μs, and the average power dissipated in the flashlamp is...

Hi, I am modeling a transducer with non-uniform electric field lines. It can be considered as a capacitor but with non-parallel plate configuration. I have modeled the electric field lines using the laplace equation satisfying the boundary conditions and considering the equipotential lines...

Hi.. I´ve been trying to solve this problem for a couple of weeks and I need fresh ideas...it´s a 30 degree piece of a 10 cm high cylindric capacitor..how can I calculate its capacitance if it stopped to be symmetric?From my point of view the field between the 2 plates shouldn´t be calculated...

for the part of Capacitance of concentric shells why Va equals that? why the voltage on the surface of a is affected by -Q/(4pi*epsilon*b), which represents the voltage on the surface of b these two voltage represents something at different position!

Homework Statement For a TeflonTM-filled parallel-plate capacitor having a plate area of 175 cm2 and insulation thickness of 0.0500 mm, determine the following: a.)capacitance b.)max volatge Homework Equations C = Q/V C = (constant)(A/d) The Attempt at a Solution I understand the gist...

I've got an iPod Touch and am trying to create an electrical circuit that, when turned on, will trigger the touch sensor in a specific spot (the spot that whatever component of the circuit provides capacitance is resting on, I guess). For the life of me, I cannot figure out how to trigger a...

Homework Statement The question is at http://dl.getdropbox.com/u/175564/capacitance.JPG Homework Equations Q = CV C = \epsilon_{0} A / d The Attempt at a Solution The right solution is Q^2 / C that is (h). I know that C is proportional to the inverse of the distance between...

Homework Statement What is an amp hour? Are they saying that batteries in series maintain the same capacitance when they say amp-hours? When connecting your batteries in Series you are doubling the voltage while maintaining the same capacity rating (amp hours). Homework Equations None...

Hello, I would like to get a method for calculation of capacitance of conductors. Let say, I have several conductors in space (2D). I know voltage everywhere between and on conductors, and I need to know the value of capacitance between 2 conductors among several. I'm looking for a general...

This formula (E = V/d) has been used to derive the value of capacitance...but how is this applicable?...this is for point charges and here we're dealing with plates. Any derivation to prove this is also applicable for plates?

Hi Friends, :smile: Two particularly abstract queries have surfaced in my mind (this seems to be a recurring problem with me! ) :biggrin: CASE 1 :- Infinite Inductance Let us consider an 'ideal' solenoid coil (zero resistance, pure inductance). It is connected to an AC supply of say...

The images tell it all. Please help someone. http://image.cramster.com/answer-board/image/200941884006337564080009162509346.jpg on this diagram, the expression IL(t) should read I(t). http://image.cramster.com/answer-board/image/2009418845296337564112974787505740.jpg

Homework Statement The giant axon of a squid is 0.5 mm in diameter, 10 cmlong, and not myelinated. Unmyelinated cell membranes behave as capacitors with 1 microF capacitance per square centimeter of membrane area. When the axon is charged to the -70 mV resting potential, what is the energy...

Homework Statement A thin conducting shell of radius a has charge q. Concentric to this is another shell of radius b (b > a) with a different charge Q. How is the charge distributed and what is the capacitance of the two shells. No hint to the relative polarity of the charges is given...

Homework Statement Ok, let's say that I have two plate disk, with an area of A and they are separated with a distance d apart from each other. I need to measure the half-life of exponential decay to calculate capacitance. I need to graph C vs x = 1/d, however how can I get C ?? Homework...

Find the capacitance of a parrell plate capacitor in pF with A=0.04 m^2 distance of separation between plates = 2mm relative permittivity of dielectric = 6 and permittivity of free space = 8.854x10^-12 C = (6)(8.854x10^-12)(0.04) / 0.002 = 1.06248x10^-9 F in pF = 1062.48 pF Thanks

Hi there I've encounted a problem in which I'm required to calculate the total capacitance between the end of a cylindrial rod and an infinite ground plane. I've attached a schematic drawing here. The gap between the rod if far smaller than the diameter...

Homework Statement In the FIGURE (shown below in "attempt at solution" section), find the equivalent capacitance of the combination. Assume that C1=10 nF; C2 = 5 nF; and C3 = 4 nF. Homework Equations For parallel capacitors: Ceq = C1 + C2 + C3 +... For series capacitors...

I was getting ready for a test in my physics class and have a question that I cannot figure out. Why does adding a dielectric to a capacitor cause the amount of charge that can be stored to increase. I understand what a dielectric is and how a capacitor works but am just not sure why this...

What is the correct voltage - current equation for a variable capacitance capacitor? If the capacitor has a fix value, C, then the following expression holds: i(t)=C*dv/dt, where i is the current that charges the capacitor and v the voltage across it. If C=C(t) then i(t)=C(t)*dv/dt...

Homework Statement A capacitor network is shown below. http://img99.imageshack.us/img99/9967/79727282.gif What is the equivalent capacitance between points y and z of the entire capacitor network? Homework Equations In parallel: C = c1 + c2 + ... In series: 1/C = 1/c1 + 1/c2 +...

1. Two capacitors, one 7.5 µF the other 15 µF, are connected in series across a 12-V battery. (a) Find the equivalent capacitance of the two capacitors. (b) Which capacitor stores more charge? Explain. (c) Find the charge stored on each capacitor. 2. Cequiv = ∑C C = Q/V 3. (a) Cequiv = 7.5µF +...

Homework Statement A uniformly charged insulating rod of length 14cm is bent into the shape of a semicircle (looks like a "C"). The rod has a total charge of (-7.50E-6C). find the electric potential at O, the center of the semicircle Homework Equations v= ke\intdq/r The Attempt at...

Homework Statement A heart dysfunction that can cause death is ventricular fibrillation. This is an uncoordinated quivering of the heart as opposed to regular beating. An electric shock to the chest can cause momentary paralysis of the heart muscle, after which the heart will sometimes...

1. The problem statement http://s685.photobucket.com/albums/vv212/dewdr0p714/?action=view&current=5circuittakehometest1.jpg 1) Determine the equivalent capacitance of the circuit 2) How many RC time constants are needed for the charge on the capacitors to reach 75% of their final...

A capacitor with capacitance of C = 8.5±1 μF has a potential difference of V = 4.5±0.4 Volts. What are the charge on the capacitor and the error in this value, in μC? To find charge I just use Q = C*V correct? And how do I calculate the error? Thank you!

Homework Statement Lighting strike: Storm clouds build up large negative charges that dwell in a charge center. Suppose a storm cloud has -25 C in a charge center located 10 km above the ground. The negative charge center attracts an equal amount of positive charge that is spread on the...

1. To make a parallel plate capacitor, you have available two flat plates of aluminum (area = 190 cm2), a sheet of paper (thickness = 0.10 mm, κ = 3.5), a sheet of glass (thickness = 2.0 mm, κ. = 7.0), and a slab of paraffin (thickness = 10.0 mm, κ = 2.0). Find each's capacitance; then enter the...

Homework Statement An empty capacitor is connected to a 12.0-V battery and charged up. The capacitor is then disconnected from the battery, and a slab of dielectric material (K = 2.8) is inserted between the plates. Find the amount by which the potential difference across the plates changes...