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

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Does current flow stop when a capacitor is fully charged?

If I take a 1V battery and a 1 farad capacitor and a bulb and connect them in a circuit. Then will after the capacitor gets charged (not fully charged as that is impossible) will the bulb gradually ...
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0answers
45 views

Self tuning 125khz RFID reader

I have a RFID reader based on the EM4095 IC. I would like to make the reader self-tuning so it can handle varying inductance in the antenna due to reading tags near metal. I had thought of using a ...
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2answers
63 views

Capacitance - Voltage characteristic diagram in a Schottky diode

I 've searched the web for that diagram with no satisfactory result. Does a schottky diode has capacitance or not because of very tiny depletion (almost none) zone ?
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56 views

Do we ever use the pin capacitance of a digital circuit component (e.g ASIC, FPGA) in doing timing or data integrity analysis

As far as I understand, the pin capacitance on say an ASIC or FPGA effects the rise and fall time of the signal on it. It is also possible that the impedance offered by this capacitance to a very high ...
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2answers
119 views

How to make LC tank circuits oscillate continuously?

An LC tank circuit produces oscillations, when the capacitor is charged and connected to the inductor, but the oscillations decay gradually. How to make it continue, i.e. oscillate continuously? I ...
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71 views

How long of a wire and how big of a load can I have for SPI bus?

I have a system where I will connect up to 128 identical magnometer ICs up to an FPGA. I am trying to decide between SPI and I2C for comms. If I use SPI the setup will require 128 + 3 wires IF all ...
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0answers
79 views

Finding the value of capacitance for a given circuit

How would you know how much capacitance you should use in your circuit or is there any formula to compute on the desired capacitance you should use on your circuit? I have this circuit (figure shown ...
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1answer
57 views

Where does the power absorbed of this capacitor come from?

In my circuits book, the voltage across a capacitor is given as \$v(t)=100\cos({2\pi60t})\$. Because \$i_{ab}=C\frac{d}{dt}v_{ab}\$, we naturally compute the current as ...
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395 views

What happens to the capacitance of a system if capacitors are charged in parallel and then put into a series circiut

If you have 2 capacitors 2V, 2F each. When you charge them in parallel, the system will have 2V and 4F when you attach a load to it. If you take the charged capacitors and then put them in series, ...
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143 views

What does an inductor's current stabilize to in DC?

As you can see from the below graph, after an inductor is turned on, the current is stabilized to approximately 6.5mA. My question is: what does the 6.5mA represent? Where did that number come from? ...
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74 views

What's the definition of “signal to ground capacitance” of a coaxial cable? What's the difference between it and normal capacitance?

What is the definition of "signal to ground capacitance" of a coaxial cable. I know what capacitance is, but I'm not sure whether it is just the same thing.
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1answer
77 views

Application of charge conservation

I don't know how to start formulating equations or finding equations for this circuit, I have to prove this by mathematical equation. My adviser told me by charge conservation but I don't know how to. ...
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49 views

Charge conservation

How can I apply the theory of charge conservation for this charge pump circuit. Specifically on the pump circuit. How do I get the charges on the capacitors?
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124 views

How to design an square wave Oscillator Circuit with 1-20 MHz range?

I need a circuit that will generate square waves in a range of 1 to 20MHz. The circuit also should be adjustable in a scale of 0.05MHz for each step. There is no need for adjustments during the ...
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0answers
48 views

Diffusion capacitance

As far as I know, capacitance is created by two conductive plate with an insulation between them as they can store charges. When a diode is in reverse bias, it shows a capacitance because the n and p ...
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1answer
118 views

Solid State Relay Capacitance Bad for Audio?

Regarding MOSFET optocoupler relays like the Panasonic AQW212, am I correct in understanding that the capcitance between the terminals and ground when the switch is open ("off") is around 100pF when ...
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1answer
240 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
116 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
86 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
105 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 ...
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1answer
180 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
113 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
69 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
74 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
105 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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2answers
134 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
87 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
140 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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2k 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
131 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
98 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
81 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
56 views

Calculate the capactance [closed]

If RV=22000 R=2200, how to calculated the C and what is the value?
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169 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 ...
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1answer
93 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
87 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
525 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
78 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
152 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 ...
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2answers
299 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
65 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
349 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
48 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
40 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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5answers
334 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
262 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
125 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
50 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
95 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 ...
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3answers
150 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 ...