# Questions tagged [capacitance]

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

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### Crystal oscillator load capacitance, again

There's a lot of seemingly conflicting information regarding how the load capacitance for a parallel resonant crystal is calculated. Faced with a lot of problems in recent years with non-oscillation ...
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16k views

If a crystal has a rated load capacitance of 6 pF, is the right thing to do to put a 6 pF capacitor to GND on either leg of the crystal? I'm using it as the clock source (TOSC) for an XMEGA and it's ...
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### What are some reasons to connect capacitors in series?

Usually you either combine capacitors in parallel because you want to increase the total capacitance while fitting the components in a certain shape/position, or you just combine capacitors by buying ...
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### 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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1 vote
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### Miller's Theorem - Input Capacitance

Please see attached image. I've become confused if the answer to this question, which uses Miller's Theorem is correct as it should not be a minus, rather it should be a plus. Please see my working ...
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### LTSpice capacitance dependend on voltage source

I am looking for a way to change the value of a capacitance dependent on the voltage source of the circuit. How do I create a voltage dependent capacitor in LT spice? Edit: Two capacitances in a row ...
8k 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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### µ in the Middle of a Capacitor Rating

I'm looking at an electrolytic capacitor (and old blue, Philips one used in electronics classes) and am wondering why it is printed with 4µ7-M. I tried Googling, figuring that it was a common enough ...
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1 vote
720 views

### Capacitor Voltage Rating

How to find the voltage rating of a capacitor after knowing the capacitance value. Example, For a power supply, If the input voltage is 60V and output is 5V. The input capacitor(C1) value is 100uf ...
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27k views

### Measuring feline capacitance

When I pet my cat, and then touch her on the nose, I get a little shock. Sometimes, when she walks up to something, her nose sparks and she jumps back and puffs out. I was wondering how I might go ...
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### Is there a dual of the transformer?

Capacitors and inductors are duals of each other. A transformer is made of two inductors, and transfers power through mutual inductance, through the magnetic near-field (right?) Also, you can vary ...
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### Reading very low capacitances with Arduino

I'm trying to measure the capacitance of a very low capacitance sensor (two parallel plates across a block of foam). This is a self-produced force sensor; I'm trying to eventually use some of the work ...
4k views

### Is a human (or other) electrical signal absolutely necessary to activate a capacitive touchscreen?

I know this is the general wisdom, and that someone has asked a similar question here: How can a capacitive touch screen be triggered without human contact? However, I didn't quite understand the ...
10k views

### How to measure capacitance without LC meter?

I would like to use capacitors salvaged from old electronics, but I currently don't have an LC meter. What would be some really simple circuits, that would convert capacitance to something I can ...
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669 views

### Flashing LED circuits

How does the current flow through this circuit and thus how do the components work together to cause the flashing LED? I know the basics in that the current first charges the capacitor which ...
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### 3 phase motor running on single phase using steinmetz delta connection

How do 3 phase motors manage to run on single phase power using the Steinmetz delta connection with a single capacitor? I thought capacitors only shift the phase angle upto 90 degrees, whereas 120 ...
3k views

### What will increase output volume (dB) on a Piezo Transducer?

I need to achieve 110dB at 25khz from a Piezo Transducer. According to the datasheet, the resonant frequency of the Piezo is 25khz and at 10 vrms it will produce 110dB. I will be using an ...
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### Capacitors and capacitance

this time I'd like to ask a few questions about capacitors, all noob questions again; What's a better idea, having one capacitor at 5x farads or five capacitors at x farads each? I want to get a ...
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19k views

### How do transposition towers in transmission lines work?

There're such things as transposition towers in power distribution powerlines. The idea is that for example you have three conductors running in parallel at the same height and the leftmost of them is ...
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### 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 ...
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### How do I decide what capacitor to use in a circuit?

I am using a voltage regulator, and to get cleaner power, the datasheet recommends using a 0.33uF capacitor. However, it doesn't say what type it wants. Stupidly, I ...
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### Why does the capacitance value of an MLCC (capacitor) increase after heating?

I have a general purpose MLCC capacitor design kit, which consists of capacitors of different values. I took a 2.2 µF (X5R, 16 V, +/- 20 %, -> this one) capacitor out of it and measured its ...
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### Self capacitance of an isolated object

A few times I've been reminded that an object can have self capacitance and it's just not registering with me how this can be so. I'm sure there's a good explanation. Here's the explanation I am ...
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### Are film capacitors affected by DC bias?

After looking around, I have found quite a few things about how DC bias reduces effective capacitance for a ceramic, or electrolytic capacitor, however nothing seems to talk about the effect on film ...
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### Understanding capacitance in oscilloscope probe tip

I am trying to understand the capacitance and resistance in oscilloscope probe tip. In the above attached image, that 9Mohm resistance is used for that 1x and 10x setting that divides the input ...
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### 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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### How does a Theremin "antenna" work?

I always assumed that the shape of the antennas was important; a vertical monopole for pitch and a horizontal loop for volume, thinking that this minimized their interference with each other. But it ...
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### How can I measure gate capacitance?

Is there an effective way to directly measure the gate capacitance of a power MOSFET, like say the IRF530N? The way my circuit is behaving would indicate that the effective gate capacitance is ...
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### 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 ...
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