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xkcd #3106: Farads (imgs.xkcd.com)
submitted 1 year ago by [B] to c/xkcd@lemmy.world
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xkcd #3106: Farads

Title text:

'This HAZMAT container contains radioactive material with activity of one becquerel.' 'So, like, a single banana slice?'

Transcript:

[Cueball holds a stick while talking with Megan and White Hat.]
Cueball: This stick is one meter long.
Megan: Cool.
White Hat: That's a nice stick.

[Cueball holds a smallish rock.]
Cueball: This rock weighs one pound.
Megan: I'd believe it.
White Hat: Looks like a normal rock.

[Cueball holds a small battery.]
Cueball: This battery is one volt.
Megan: Seems fine.
White Hat: Might need a recharge.

[Cueball holds a capacitor while Megan and White Hat panic.]
Cueball: This capacitor is one farad.
Megan: Aaaaa! Be careful!!
White Hat: Put it down!!

Source: https://xkcd.com/3106/

explainxkcd for #3106

'This HAZMAT container contains radioactive material with activity of one becquerel.' 'So, like, a single banana slice?'
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[–] 1 point 1 year ago (4 children)

Capacitors can be used to remove ripple from a DC current. Ripple is basically alternating current that is running along a DC current. So, attenuation, I believe, is the correct terminology.

They generally don't completely get rid of AC, and they don't perfectly filter it out unless they are perfectly matched for the AC, and even then, I don't know of any capacitors that are used in lieu of a full-bridge rectifier or half-bridge rectifier to convert AC to DC.

I could very well be wrong. I am far from an electronics expert, But this is what my understanding tells me.

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  • [–] 1 point 1 year ago (3 children)

    Well youre not far off. They are used to filter ac, not convert it. They act as low-pass filters which means if you have a setup which is a 100khz low-pass filter it means it only lets through frequencies that are under 100khz. There are of course more accurate but complicated ways of explaining this but that is out of scope for this comment. Also nothing is perfect in the real world but you can calculate how much of the signal it lets through.

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  • [–] 1 point 1 year ago (2 children)

    but you can calculate how much of the signal it lets through.

    Shouldn't that be "noise" instead of "signal"?

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  • [–] 3 points 1 year ago (1 child)

    I mean depends on the context, in the specific case which i was thinking of it is signal but usually its noise. I have mainly worked with ac and dc signal coupling so thats why both sre signals for me when i think if it.

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  • [–] 2 points 1 year ago

    That makes sense. In distortions for music instruments all of it is signal for instance. It's just that sometimes you don't want all of it because you want a specific sound to be produced.

    I'm most used to working with digital electronics with a crystal supplying the frequency, so for me anything that is above that frequency is noise.

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