Capacitance is the ability of a body to store an electrical charge

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219 views

What is the role of the capacitor within the assembly

I have some questions regarding my assembly and especially on the role of the capacitor within the circuit. Before I added the capacitor I encountered 2 issues: when the piezo was squeezed (a ...
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1answer
84 views

Minimum number of capacitors

I require a capacitance of 2×10^-6 F in a circuit across a potential difference of 1kV . I have a large number of 1×10^-6 F is available which can each withstand a potential of 400V. Suggest a ...
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1answer
47 views

how to select capacitor for a crystal oscillator

Here is a 32 MHz crystal from one of TI's reference design The BOM list defines the crystal as ...
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2answers
91 views

Dielectric can be insulators?

People say that dielectric should be an insulator so that it can decrease net electric field increasing capacitance.. My question is if the object is a insulator how does the object get polarized ...
0
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1answer
95 views

What capacitors do when it is connected in Series and parallel to a AC input

I have seen in many circuits the capacitors are connected in series and parallel with the AC line. What the capacitor actually does when it is in series and parallel. I know capacitors passes AC ...
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2answers
87 views

Replace motherboard capacitor with lower capacitance?

Is it possible and safe to replace a motherboard capacitor of 1800uF, 6.3V with a capacitor of slightly lower capacitance 1500uF and the same voltage 6.3V? My motherboard does work, but it tends to ...
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2answers
63 views

Capacitive reactance

I'm doing AC theory as an electrical apprentice now, and my lecturer said that inductive reactance and capacitive reactance both work with Faraday's law, or back-EMF, is this correct for capacitive ...
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1answer
63 views

Measurement and characterization of a non-linear capacitance

Background I am studying a device that is a non-linear capacitance. In fact, structurally it is two parallel plates with a charged fluid in between the plates. The charged species of the fluid can ...
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1answer
43 views

Two-port network: find fundamental parameters

What is the easiest method to find the ABCD parameters? I tried replacing the middle part of the circuit (R2,L,C) with an equivalent impedance and then finding U2 depending on U1, but it is very ...
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125 views

How do capacitors maintain their charge?

If a capacitor is connected to a copper circuit and a battery, electrons would travel to one point of the capacitor plate, then a negative charge will build up because of the presence of excess ...
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2answers
67 views

Why are the values im getting through a capacitive sensor decreasing as the resistance gets lower

I'm currently messing around with "capacitive sensors" by trying to light an LED using an Arduino.My capacitive sensor that i am using is just made up of an Arduino,3 wires and a resistor.My set-up is ...
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3answers
134 views

Communicating with the moon via capacitance

In the question Capacitance between Earth and Moon, several answers gave a value for the capacitance between the earth and the moon at tens or hundreds of µF. Since capacitors are conductive to AC, ...
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2answers
1k views

Capacitance between Earth and Moon

Is there a capacitance between the Earth and the Moon, and if there was enough potential difference, could a discharge strike occur?
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1answer
68 views

Large photodiode capacitance

I'm working with an avalanche photodiode with a 320 pF capacitance. What exactly are the downsides of suc a photodiode with large capacitance values? I assume they would be slower due to the narrower ...
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2answers
67 views

Capacitance and Inductance properties of coaxial transmission lines

I'm interested to understand what affect the capacitance (between cable core and shielding) and the inductance have on a signal transmitting down a coaxial cable.
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1answer
64 views

Is to possible to measure electric signals using a capacitive touchscreen?

Thanks to a very good explanation by Mr. Ghosh, I found that a capacitive touchscreen measures the change in capacity, induced by contact with a conductive material, along a grid. I have two ...
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1answer
55 views

Calculate the capactance [closed]

If RV=22000 R=2200, how to calculated the C and what is the value?
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2answers
118 views

How to create a touch switch to use with a Raspberry Pi

I'm trying to make my own wakeup lamp. I have a lamp with a large metal base to hide all the components in. I also have a Velleman K8064 DC Controlled Dimmer Kit which I have put together and is ...
1
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1answer
85 views

LED only lighting up when my hand is hovering over it

I've got a pretty basic circuit, running an 10-segment LED bar graph through two TI HC595 shift registers. The very strange thing is that when I run the whole setup, and turn on a few of the LEDs, ...
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1answer
78 views

Find the capacitance of this rectangular slab of two films of metal virtually 0 thickness and 2 sheets of plastic. Then it is rolled into a cylinder

this question may be pretty simple for some people on this forum. Here's a basic image to go with the question. (also here) Two films of metal, virtually 0 thickness and 2 sheets of plastic. Find ...
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3answers
433 views

If MOSFET is a voltage-controlled device, then why do we need to supply it with high current when using in an H-bridge?

I might be confusing myself, but from what I am reading so far, a BJT is a current-controlled device and a MOSFET is a voltage-controlled device, which to me implies that a MOSFET requires very low ...
3
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1answer
67 views

Resistivity and resistance. Permittivity and?

We know that resistance is dependent on both the materials resistivity and the geometry of the material. For a cylindrical or rectangular material the resistance is: $$R=\rho*\frac{l}{A}$$ where l ...
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1answer
141 views

Capacitance of two wires with a grounded wire between

I have measured the capacitance between wires number, say, 1 and 3. With the wiree #2 just floating, the result was 390 pF. But after i have grounded the wiree #2, the capacitance was 220 pF. What is ...
4
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2answers
270 views

Making a grounded object capacitive

I am trying to make a copper pipe which is placed in a natural park capacitive. It is placed in the soil meaning that it is already grounded. I am using a basic arduino and their capacitive sensing ...
2
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1answer
49 views

load switch capacitance constraint

Considering using a Load Switch like DigiKey FDC6330LDKR-ND for powering on and off a device at the far end of a cable. The voltage and current requirements are well within spec however load ...
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1answer
166 views

How do I calculate the capacitor value (Farad & Voltage) given the pulse current, pulse duration & maximum tolerable voltage drop?

I have an electronic component with following characteristics: Operating voltage: 4.5V Peak operating current: 2000mA for 600uS every 4000uS. The device can ...
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1answer
42 views

Measuring self-capacitance of coils

Is there a simple way of measuring the self-capacitance of a coil? There are many estimates out there for self-capacitance based on number of turns and wire specs, but I'm wondering if I can do an ...
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1answer
39 views

Is the Delay in Strain Data Due to Capacitance?

I have designed a sensor board which gives a strain o/p based on wheatstone bridge principle(change in stress is measured through change in resistance). But the starting value is not at zero level,it ...
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4answers
174 views

Circuit capacitance question

Given the following circuit, what ways there are to calculate its total capacitance? Thing is this is not a simple case, and I can't really decide which part is parallel and which is a series, ...
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1answer
121 views

Looking for a transparent conductive spray/paint/ink

I know there are conductive sprays available, but these are strongly coloured due to the metals inside them. I am trying to make a (dry) wooden surface capacitive, but would like to have the feel and ...
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1answer
116 views

DIODE as capacitor?

How does Diode act like a capacitor when voltage across diode is less than forward voltage spec. Basically when diode is turned off? What is its usual capacitance when diode (zener) is turned off.
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1answer
49 views

Approximation of ideal capacitors?

Capacitors are often approximated as infinite conducting plates. I find this approximation surprising since the capacitors I've seen in circuits are only a few centimetres big. For all the ...
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2answers
91 views

Capacitance to Analog Voltage

I've been looking at theremins recently. I've built a simple one using heterodyne oscillators, but I was wondering how to make a capacitance detector similar to the theremin's antennas. Basically, a ...
2
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3answers
137 views

How does a dielectric alter the electric field?

My textbook is trying to explain why adding in a dielectric between two conductors causes a change in the field inside. They provide the following image: I don't understand how the second image is ...
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3answers
457 views

Violation of conservation of energy?

Say I have a parallel plate capacitor that has a vacuum between the plates and has electric energy U. If I then add in a dielectric between the plates while the capacitor is charged, the electric ...
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4answers
327 views

Capacitors in series?

Capacitors in series have identical charges. We can explain how the capacitors end up with identical charge by following a chain reaction of events, in which the charging of each capacitor causes ...
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0answers
94 views

Understanding how bypass caps work, mathematically

Assume there is a band of noises that you you want to filter with center frequency Fn. Then The complex voltage representing noise at frequency F is V_(F, T) = V(F) e^(i W(F) T), where V(F) is the ...
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1answer
136 views

Grounding Plexiglass

I have a sheet of plexiglass that has metal strips (Aluminum) that will be connected through wires to an Arduino. The Arduino is grounded but the metal strips are not. The metal strips will rest on ...
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0answers
24 views

Influence of a Capacitance Matrix of a voltage measurment

I am having a problem in understanding how, in a multiconductor system, the Capacitance Matrix influences the measure of voltage between two electrodes. In the case that interest me we have 4 ...
3
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4answers
561 views

How to calculate equivalent capacitance to a battery?

I have a 1.25V 2Ah battery and I'm trying to calculate a equivalent capacitance with rated voltage of 2.7V for each of those batteries. This is what I did: Work of Battery = \$1.25V * 2A * 3600s = ...
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0answers
308 views

how to find the value of a capacitor/varactor in cadence virtuoso

I've been given a MOS varactor model and layout to use in a project, and I need to be able to plot the capacitance as the applied voltage is swept. I don't know how to do this in Cadence and ...
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0answers
69 views

Children's board book - embedded electronics for question and answer - capacitance sensor?

What are the components needed for a system to implement the following: A children's board book with multiple choice questions on each page a child will use an electronic stylus device (with ...
14
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3answers
1k views

Why need the capacitors be as close as possible to the device?

Just a simple question: what exactly stands behind the need for placing the capacitors as close as possible to the current consuming device's pins? Is that the inductance, resistance or maybe ...
0
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1answer
58 views

Multiplexing and electric capacitance

I'm working on a project, it's basically a hand-drawn paper keyboard based on capacitance. I was thinking I can multiplex the different lines with shift register (74HC595) and switch (4066), and as ...
10
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1answer
179 views

Why do capacitors across my FETs minimize ringing/distortion?

I'm designing a 24V to 350V DC-DC Converter based on a H-Bridge. The power requirement is 500W and the circuit operates at 20KHz. The design works fairly well and I've achieved about 90% efficiency at ...
18
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1answer
566 views

What effect does selecting the wrong load capacitance for a crystal have?

I've seen questions such as this one and this one that talk about selecting capacitors that, in series, match up as closely as possible to the load capacitance of the crystal. What effect does ...
0
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1answer
206 views

Initial Conditions and current for an RLC circuit

It is required to find \$i_L\$ and \$v_c\$. It is quite easy to find \$v_c\$ from \$i_L\$ using simple integration. So, for now finding \$i_L\$ will be the concern of the question. Prior to closing ...
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3answers
320 views

Measure capacitance in softwire using Tina/Multisim/other simulators

Is there a way to measure capacitance of a capacitive network as shown below in Tina-TI, Multisim, or other simulators? I tried searching but I couldn't find any way to measure capacitance directly as ...
3
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3answers
206 views

Does current lead voltage during discharge in capacitors?

I can see that how current leads voltage while capacitor is charging. Looking at any capacitor charging diagram will explain this: (e.g figures in http://en.wikipedia.org/wiki/RC_circuit) However, I ...
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398 views

I2C and SPI Bus Routing

When routing an I2C (SDA, SCL) bus or SPI (SCLK, MOSI, MISO) bus to multiple slaves is it preferred to wire the slaves in parallel or series? Below are two diagrams with distances labeled to help with ...