Capacitor Definition and 1000 Threads

This is a long post. Sorry... 1. Homework Statement We are given a spherical capacitor with an inner conductor of radius ##a## and outer conductor of radius ##c##. The space between the conductors is half filled (##a<r<b##) with a dielectric with permittivity...

Homework Statement A capacitor of capacitance 12*10^6 is fully charged from a 20V d.c. supply. i Calculate the charge stored by the capacitor. ii calculate the energy delivered by the dc supply iii calculate the energy stored in the capacitor. iv account for the difference between your...

Consider a capacitor which is charged to a certain voltage 'V' and having a total charge 'q' in it.The leads of the capacitor are connected to ideal conducting wire strips.Now if I introduce one conductor slab between plates of the capacitor, without touching the plates,as we know from basic...

I've been asked to do an electric bug swatter in class, and several questions have come up to my mind. Whenever two rackets (each connected to a different terminal on the capacitor) touched, a spark emerged. This spark is supposedly ionised gas, which makes sense. But why do people say that...

Hello there, I want learn to do homogenous differential equations and I cannot work out what is wrong in this example. Hope you'll be able to tell me why my DE is unsatisfactory. Assume that a capacitor is has charge Q and that the terminal with the high voltage is connected to a switch in...

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.

Homework Statement A capacitor of capacity C is charged with potential difference V. Another capacitor of capacity 2C is charged to 4V.they are connected with reverse polarity after removing batteries. The heat produced during redistribution of charges is... Homework Equations ##Q = CV## ##U...

I was going through the capacitor lesson in my textbook. In it its written "...both positive and negative plates will produce electric field in the same direction, hence the electric field adds up...outside the plates, electric field is zero since the field due to negative and positive charges...

Homework Statement In each of the four circuits shown, an AC input voltage, ##V_0 cos(\omega t)## is applied on the left and the output voltage is measured on the right. Treat the input frequency as a...

Homework Statement a) How much energy in microjoules is stored in the capacitor at t=500 micro sec b) Repeat (a) for t=infinite Homework Equations Will be on attachment The Attempt at a Solution I am not sure how to approach the problem.. The graph shown is a graph of amps respect to time. So...

Can't find an answer to my question. Why do capacitors are so special when it comes to purity, unlike resistors and inductors. I know the capacitor somehow impedes the inductance in the circuit, but how? I just began studying the ac theory, and it boggles my mind.

Homework Statement There is a circuit with a battery of voltage V and resistor R, then splits into two branches one with a capacitor C, and one with a resistor 2R. The answers for the questions can only depend on R, C, V, and t. When a switch only allows current to flow through the capacitor...

So electric field tells us the force per unit charge that is felt by a test charge at a distance d from a source charge. So it tells us that the closer the test, or other charge, is to the source charge ,the stronger the interaction, and also that the larger the source charge, the stronger the...

Homework Statement Between two metal plates a metal strip is inserted as shown on the figure. a) Calculate the electric potential anywhere inside the capacitor. b) Simplifly ##U(x,y)## for ##x>>a##. c) Calculate the electric field in the middle of the capactior. Homework EquationsThe Attempt...

$$\epsilon=IR+V_C$$ $$\epsilon=IR+\frac{Q}{C}$$ $$\frac{dQ}{dt}=\frac{\epsilon-Q/C}{R}$$ $$\int\frac{dQ}{C\epsilon-Q}=\int\frac{dt}{RC}$$ $$-ln(\frac{\epsilon C-Q}{\epsilon C})=\frac{t}{RC}$$ in previous step I am confused as to why the εC is in the denominator. if we have...

I have a capacitor bank (20x 330v 180uF capacitors in parallel). But i don't have 330v DC power supply to charge the capacitors to 330 volts. I tried using a 13.7v supply from an AC adapter, but the capacitors got charged only to 13.7v. What should i do for this?Should i use another capacitor...

Homework Statement An electron with a speed of 5.0x10^6 m/s is injected into a parallel plate apparatus, in a vacuum, through a hole in the positive plate. The electron collides with the negative plate at 1.0x10^6 m/s. What is the potential difference between the plates? Vi= 5.0x10^6...

Homework Statement My question is: If we have a parallel plate capacitor with 2 parallel dielectrics both taking A/2 of the complete surface, is the total electric charge equal to sum of the electrical charges in the first dielectric and the second dielectric, i.e is qtotal=q1+q2=σ1*A/2+σ2*A/2...

Homework Statement 1. In the circuit shown below calculate how long itwill take to charge the capacitor C2 to 4 V and how long it will take then to discharge it to 1V. Homework Equations The Attempt at a Solution I tried to solve it by taking t=0 when v=0 to get the k which is then...

Homework Statement An electron enters a region between two capacitor plates with equal and opposite charges. The plates are L=0.1 m by d=0.05 m, and the gap between the plates is h=0.002 m. During a short time interval of dt=0.002 s, while between the plates and far from the edges, the change...

Homework Statement For the circuit shown in the figure, the switch has been open for a very long time. (a) What is the potential drop across the 15.0-mH inductor just after closing the switch? (b) What is the potential drop across the 70.0-µF capacitor after the switch has been closed for a...

I'm a bit confused about the electric field above a plate. First, I have come across the equation E=kQ http://www.sparknotes.com/testprep/books/sat2/physics/chapter13section3.rhtml which in many ways makes sense to me because around a point the field would be proportional to 1/{r^2}, and then...

Hi All, I understand that when a capacitor is subjected to a DC voltage, it stores charge. However, when the DC voltage is removed (open circuit) why does the capacitor not internally discharge? Shouldn't the charge just go back to where it was, leaving the capacitor with 0 stored charge? I am...

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...

Hope I can get some help here. I have a 1-1/2 hp. 115/230 volt single phase induction motor I want to use as a small generator. currently it's wired for 115 volt I need help with the math to calculate the proper capacitor/s to use. Running no load amps as a motor draws 18 amps. Name plate...

Homework Statement I am trying to find the electric and magnetic fields between two parallel circular plates, where one plate is grounded and the the other has a voltage that increases linearly with time. I need the E field between plates, and I can ignore fringing fields. The permativity is...

Homework Statement Homework Equations Here is the technique I am using: The Attempt at a Solution [/B] I understand how to solve the problem using the technique provided by the solution but I was wondering where I messed up in the technique that I used. I prefer the second...

A capacitor is formed from two concentric spherical conducting shells separated by vacuum. The inner sphere has radius 10.5cm , and the outer sphere has radius 15.5cm . A potential difference of 110V is applied to the capacitor. What is the energy density at r= 10.6cm , just outside the inner...

Homework Statement This homework problem is for my power electronics course I am currently taking. The network shown to the right (SEE ATTACHED IMAGE) is used to study the output voltage ripple of particular types of dc-to-dc converters. Note that \tilde{i}(t) and \tilde{v}_C(t) represent...

Homework Statement The number of 2 uF, 400 V capacitors is needed to obtain a capacitor value of 1.5 uF rated for 1600 V is..... Homework Equations The Attempt at a Solution equating the energy on both sides, 1/2*2*400^2*n=1/2*1.5*1600*1600, n=12, here n = number of capacitors...

Homework Statement 1. The distance between two parallel plates is increased while they remain hooked to a battery. Which one of the following statements is true? The voltage between the plates will decrease. The electric field between the plates will increase. The charge on the...

Homework Statement A parallel plate capacitor is constructed with plates of area .0280 m^2 and separation .550mm Find the charge on each plate when potential difference between plates is 20.1V. what separation would be necessary to give a charge of 20 nC on each plate?Homework Equations Im...

I am troubleshooting a 1967 GE synchronous motor used to run a reciprocating compressor. It is a 1000 HP machine. I am trying to figure out the size and purpose of the capacitor connected to the DC field. Is it there to absorb voltage fluctuations? The capacitor has burnt up and can't be...

Homework Statement A source of ε = 10V, capacitor of C = 5 μf, inductor of L = 15 mH and r = 10 Ω and a resistor of R = 100 Ω are connected as in the schematic (attached). How much heat will dissipate in the resistor after the switch is opened? Homework Equations dQ = I2Rdt KVL The...

In a purely capacitive ac circuit, we get, Im = Vm*ω*C, ...(1) Where, Im = Amplitude of the current Vm = Amplitude of the voltage Now, what I think is, We know that in a purely capacitive circuit, voltage lags behind current by a phase difference of ∏/2 rad. So, at any time 't', I = Im...

Homework Statement A current i(t) as shown in the figure is passed through a capacitor. the charge (in micro coulomb) acquired by the capacitor after 5 micro seconds Homework Equations here slope is given for 3 microsecond ie. current=dq/dt = 2.5 charge upto here = 3*2.5=7.5 micro...

Let's say we have a simple circuit consisting of a power supply and a resistor, and currently the input voltage is 0V. We now apply a voltage of 5V to the circuit (like a step increase - instantaneously). The voltage across the resistor changes instantaneously to 5V. If a capacitor is...

Hi there What does it mean when there is a viltage across the plates of the capacitor please make the explanation easy and I would be so grateful. Thanks in advance.

Homework Statement When it comes to charging a capacitor I'm under the impression that when a parallel plate capacitor is hooked up to a battery, that electrons simply flow from the negative terminal to the plate that is connected to the negative terminal, causing that plate to become the...

Consider a parallel plate capacitor with layers of dielectric between its plates somehow that the interfaces between them are parallel to the plates of the capacitor. If the surface charge density on the plates of the capacitors be \sigma , gauss's law gives D=\sigma which is the same inside...

I can't really be too specific, but from what I remember, how do we plot a capacitors charge for different objects?

So I was looking up what causes thunderstorms online and found this: "As hail moves within the cloud it picks up a negative charge by rubbing against smaller positively charged ice crystals. A negative charge forms at the base of the cloud where the hail collects, while the lighter ice crystals...

If i have a parallel plates capacitor , where the plates have different charges , eg, one plate has 1 C of charge and the other is neutral , what's the potential difference? what if i grounded the neutral plate , will it gain 1 C of charge?

Hi, I am planning to run a DC motor using a super capacitor. The specification of the motor are: Voltage : 90V - 120 V DC Current : 15 A Duration : Should run for atleast 10 seconds. I have finalized this super capacitor from maxwell for the above operation...

I'm using 250V 2200uF capacitor to discharge high instantaneous current into an inductor as shown in the attached image. I'm using a 12 Volt battery fed into an inverter that output 220 VAC which then is fed into a rectifier which outputs 220VDC. My question; Can I connect the 220 VDC...

I made two conductive plates out of aluminum foil wrapped around cardboard pieces i don't have a micrometer with me to measure to the thickness of my paper, so i just googled the average thickness of paper; also just googled the relative permittivity of paper..$$C=\epsilon_r \frac{A}{d}$$...

Hi, Please watch the following video: If the capacitor did store charge on metal plates, like we believe today, in opposition to Steinmetz, how come no spark was produced when the metal plates touched? This must mean the glass is storing electrical energy, and that the metals do...

Hello everyone, I was wondering how one would calculate the three-dimensional charge density (per volume) in a capacitor plate with a given thickness. I know how to calculate the charge density on the surface based on the capacitance and voltage, but how would one calculate the comprehensive...

Definition/Summary A capacitor (or condenser) is something across which charge cannot move, but across which an accumulation of charge on one side can affect charge on the opposite side. So a capacitor does not conduct direct (DC) current, but does conduct alternating (AC) current. The...

The capacitor and dielectric Homework Statement A small dielectric plate is pushed between parallel plates of an (1) isolated capacitor to the half of its length. If the dielectric is let to move freely, what's going to happen to it? (2) What would happen with the dielectric if the capacitor...