Capacitance Definition and 874 Threads

Homework Statement The graph below shows the voltage across a 100 μF capacitor vs. time. Find the current (Ix), the power delivered (Px) and the energy stored (Wx) at time tx = 8 s. The attempt at a solution I found the current, Ix using the capacitance multiplied by the slope...

Homework Statement Two long, cylindrical conductors of radii a_1 and a_2 are parallel and separated by a distance d, which is large compared with either radius. Show that the capacitance per unit length is given approximately by C=\pi\epsilon_0 \left(\ln\frac{d}{a}\right)^{-1} where a...

Hi, I have deposited a film of dielectric on SiO2 substrate. Then, deposited metal dots on the top of dielectric film to measure electrical properties. I want to measure capacitance using metal dots on the top of dielectric. Since I have SiO2 as a substrate, I can not make a parallel plate...

Hi everybody. I have been doing some experimental heat loss calculations on a sealed cube of fluid, filling the volume of the cube with hot water then sitting it in a larger tank of fluid at a fixed cooler temperature and monitoring the drop of temperature inside the box. I have also positioned...

Hello everyone, I hope this is in the right section. if not i'll be happy to move it. Anyways i have a few questions about general concepts so this may be a lengthy one. Any and all help is REALLY appreciated. I have attached two photos of something explaining the creation of a magnetic...

Homework Statement a dielectric of dielectric constant 3 fills three fourth of the space between the plates of a parallel plate capacitor. What percentage of the energy is stored in the dielectric. Homework Equations U=CV2/2 = epsilon0AV2/d.2 The Attempt at a Solution When...

I'm trying to trigger a human touch in a capacitive touchscreen without the 'human' part. I've noticed that the negative pole of a battery triggers it if you are currently holding it. Or if you use the edge - why only the edge? - of a wire touching the battery and your hand. I also attached a...

Hello. I know the formula for capacitive reactance is 1/2PIfC. The function says that if frequency is constant, the Xc increases as C decreases. Question is, in a 60 hz system, stray capacitance in wire does not turn a jumper into an infinite impedance. A piece of wire 1 foot long had...

I thought capacitance was a function of geometry. So how come when we put in a dielectric in between a parallel plate capacitor it increases the capacitance. Is this because we can increase the E field in between without worrying about dielectric breakdown. Or does it have something to do with...

why doesn't capacitance decrease with increase in temperature?? It is known that conductivity increases with temperature.This is because heat provides kinetic energy to the electrons in a substance,thus increasing the rate of "flow" of electrons.Considering this,the electrons in a dielectric in...

Homework Statement Find the equivalent capacitance of the infinite system between points a and b (see figure). Where Vi is the potential difference in the number i capacitor. Homework Equations Q=CV The Attempt at a Solution For number i capacitors we have the relations Q_i=CV_i...

Calculate the charge Q1, on the positive plate of capacitor. In a previous step in the problem I found the Ceq to be 7.6E-6 and know this to be the correct answer. Q=VCeq I used the equation above but the number I found was incorrect. I am also asked these question and I have no idea what...

What is the equivalent capacitance of the network. Parallel: C1 + C2 + C3 + Cn = Ceq Series: 1/C1 + 1/C2 + 1/Cn = 1/Ceq I added C2 C3 C4 and C5 as parallel and then added this to C1 as a series.

Hi, I have been looking for some current source DAC, and have found a few types but I am having issue reading the datasheet. Some of them give the output min and mac I that the DAC can provide, which makes sense to me but other give input capacitance and "some type" of voltage. Can you...

I think I know the answers to the question I am going to ask but I am just going to make sure. This is going to be quite simple for most of the experts here so here goes: If we have a parallel plate capacitor and we double the distance between the plates while keeping the charge Q on the...

1.Suppose that a blood vessel is 2.5 mm in diameter, the magnetic field is 0.08 T, and the electromagnetic force is 0.10 mV. What is the velocity flow of the blood? Assume that blood carries charged ions. Homework Equations B=F/qvattempt looking for v isn't possible since I have no idea how to...

Homework Statement i have a graph or r against V and to make it a straight plot i then plotted ln(r) against V, Homework Equations The Attempt at a Solution the problem is i dnt know how to find the capacitance from the graph. it definitely isn't the gradient or the point of...

Hello, I have a question regarding the equation q=CV, where q is the charge and V is the potential difference of a capacitor, and C is the proportionately constant C of the capacitor. From what I understand, the value of C depends only on the geometry of the plates and NOT on their charge or...

Hi all How to calculate the capacitance of a sphere-plane system by using conformal mapping? Thanks

Understanding "capacitance" formula In this formula http://img810.imageshack.us/img810/9127/capacitance.jpg 1) What does it mean the area of overlap of the two plates? Does it mean the "area" of the plates? And, is the area of one plate always the same size of the other plate? And also, 2)...

Homework Statement For the circuit in the link below, find C equivalent: https://picasaweb.google.com/lh/photo/-p0vPLyvxZ_W_sXiWEIikDlT_BqmZyKP1qROOFyElOQ?feat=directlink Homework Equations The Attempt at a Solution I tired many ways to solve this but the middle branch...

Hi there, first, I apologize for my poor English. I made a simulation model and get results from HFSS Model has a equivalent circuit like that.(1) I run that model and get pair of solutions 'frequency vs response' like S parameter for each frequency. So, with these results, is it possible to...

Homework Statement For the capacitor circuit shown below: A. Find the equivalent capacitance B. What is the charge on the 3\muF capacitor? Homework Equations Q= C\DeltaV Parallel= C1 +C2+C3 Series= (1/C)=(1/C1)+(1/C2)+(1/C3) C1= 8\muF C2= 5\muF C3= 3\muF The Attempt at a...

Homework Statement A capacitor is formed by two concentric spheres r1= 30 cm and r2=15 cm, with a liquid insulant between them with relative permittivity Er=4. The potential difference between the spheres is 1 kV. Find: 1. capacitance 2. maximum field strength in the gap between the two...

Consider a series RLC circuit. The applied voltage has a maximum value of 120 V and oscillates at a frequency of 81 Hz. The circuit contains a variable capacitor, an 820 \Omega and a 3.7 H inductor. Determine the value of the capacitor such that the voltage across the capacitor is out of phase...

Homework Statement A capacitance of 2\mu F having a charge Q_0 is switched into a series circuit of 10\Omega resistance. Find Q_0 if the total energy dissipated in the resistance is 3.60 mJ. Ans. 120 \mu CHomework Equations Q=CV The Attempt at a Solution E=\int_0^\infty p(t)dt=\int_0^\infty...

Homework Statement A capacitance of 60 \mu F has the voltage waveform shown in Fig. 2-36. Find P_{max}. [PLAIN]http://img828.imageshack.us/img828/5255/unled2copy.jpg Homework Equations p(t)=i(t)u(t)=\left(C\frac{du(t)}{dt}\right)u(t)The Attempt at a Solution When is power at maximum? Is it...

I've made some capacitors association exercices and i got stuck on 2 of them. Q1: Q2: How can i get the equivalent capacitance on this 2 capacitors systems? Ty

for what values of C1, C2, and C3 make the terminal pairs equivalent? i know the 2f and 1f capacitance are in series: (1*2)/(1+2) = 2/3 and i know the 1/2 f is parallel to the preceding capacitors: 2/3 + 1/2 = 7/6 but i am unsure where to go from here... any help would be...

Homework Statement Two large conducting sheets are charged with a positive surface charge density. They stand vertically facing each other a distance d apart. a.) suddenly, we shrink the left sheet to a square with sides equal to d, what is the field at the point along the central axis of...

Homework Statement If each capacitor is filled with a dielectric material (with constant K, kappa), what is the new equivalent RC circuit? All resistors have equal value, and capacitors have equal value (without a dielectric), C. Homework Equations C = (Epsilon * Area) / Distance C with a...

I'm given that a 2.0\mu F capacitor is charged with 300V and 6.0\mu F capacitor is charged at 150V. They are then disconnected from the batteries and connected to each other. I correctly got the net charge between their plates as 3.0*10^{-4}C, however I can't get the charge on each capacitor...

It was told many times by my teacher that a disconnected metal plate and an earthed metal plate, forming a capacitor, will have the same charge regardless their seperation. I understand how the charge of the disconnected metal play remains unchanged, but I don't really understand how the...

Hi, I'm looking for an equation which links capacitance to the phase difference between two microphones (picking up audio from a loudspeaker). (the speaker gives off a signal at 3 kHz). My experiment, at the end of the process, was devised to be linked into the setting of microphone...

Homework Statement A solenoid with self-inductance L=2H and carrying a steady current of 1 A has the current source suddenly turned off. What is the minimum capacitance that should be connected across the terminals of the solenoid in order to prevent the potential difference generated by...

Homework Statement C120 uF C2=40uF C3= 50uF if no capacitor has the capacity to bear more than 50V then maximum potential difference between the two ends is Homework Equations Q=CV The Attempt at a Solution i tried by calculating the Ceq then putting it in the equation finding...

Homework Statement To find the capacitance of parallel plates, I am first finding the E field using gauss. However I don't know what the gaussian surface will be. I don't think it will be a gaussian pillbox as the plates aren't infinite, but will it be a sphere?? On a side note, if I...

A 16 V battery, a resistor with R = 106Ω and a 6-μF capacitor are connected in series with a switch. Find the time taken for the capacitor; a) To charge to a voltage value of 12V b) Time to discharge to a value to 7V, after it has fully charged to 16V a) V_c = V_o \cdot \left(1 -...

Homework Statement The Attempt at a Solution There were 4 parts to find net capacitance across AD, FE, AE and AO I need help with AO and i don't have any idea how to do it

Hello everyone, I have been tirelessly searching the net trying to find out how to calculate the distributed capacitance of a multi-layer bifilar coil. Just wondering if anyone here can point me in the right direction?

Hi everyone In most problems I've seen involving capacitance of a coaxial cable, there is an inner cylinder of radius a with +Q charge and and an outer cylinder of radius b with -Q charge. The voltage is calculated from a to b. However, in this problem the inner cylinder is -Q and the outer...

Homework Statement A flashlight uses 6.0J in 1.8ms (0.0018 seconds). First question: find the power. Got it: 3333W (3.3E3 with two sig figs, which is the accepted answer in the online system). The real problem: find the capacitance if the flashlight uses 200V. Homework Equations Power =...

Homework Statement A parallel plate capacitor of capacitance 5.2 µF has the space between the plates filled with a slab of glass with κ = 4.0. The capacitor is charged by attaching it to a 1.8-V battery. After the capacitor is disconnected from the battery, the dielectric slab is removed...

would a 1.5 volt electronic device that measures capacitance to turn on or off a regulator that controls water flow affect a defibrillator or pacemaker? Another way to ask this, A kitchen faucet that is touch sensitive would be safe or not safe for a heart patient who has defibrillator and...

Homework Statement Basically we did a lab on charges, capacitors and voltages. We used a 2200uF capacitor and we hooked it up with a 10kΩ Resistor connected in series with a DC Supply. The DC Supply was turned down to 0V and all the other senors were "zeroed" out. Simultaneously, when...

The energy of an RLC circuit decreases by 1.00% during each oscillation when R=2.00 ohms. If this resistance is removed, the resulting LC circuit oscillates at a frequency of 1.00 kHz. Find the values of inductance and capacitance.

1. The base of a cloud has an area of 2*10^7 metres squared and is on average 1km above the ground. treating the base of the cloud, the ground and the intervening air gap as a parallel plate capacitor, calculate the capacitance.[relative permittivity of air = 1.0] 2. I tried to say C...

Homework Statement The capacitance of the variable capacitor of a radio can be changed from 100 to 350 pF by turning the dial from 0° to 180°. With the dial set at 180°, the capacitor is connected to a 130 V battery. After charging, the capacitor is disconnected from the battery and the dial...

What is the equation or conversion factor?

hello i need some explanation on this . I know that when a battery is connected it provides constant voltage across the capacitors. But the happens when the battery is disconnected. What happens to the voltage, the capicitance, and what is the importance of dielectric. I have read the book...