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xkcd #3106: Farads (imgs.xkcd.com)
submitted 1 week ago* (last edited 1 week ago) by xkcdbot@lemmy.world to c/xkcd@lemmy.world
 

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

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[–] ch00f@lemmy.world 57 points 1 week ago (10 children)

I used to teach AP physics to kids on the weekends. One asked me why Farads were so big. I had to explain that there’s a fixed ratio between Farads, Volts, and Joules. One of them had to be crazy big or crazy small.

See also Coulombs.

Caps are especially scary because they can develop their own charge through static electricity, so large value caps are often shipped with their terminals tied together.

[–] ViatorOmnium@piefed.social 27 points 1 week ago (9 children)

There's nothing in the SI system that says ratios have to be between base units. Units that involve mass are defined against the kilogram not the gram.

[–] bizarroland@fedia.io 16 points 1 week ago (1 children)

The kilogram is just a thousand grams, so if they're tied together, they would still be tied together.

[–] bisby@lemmy.world 30 points 1 week ago

Right. 1F = 1C/1V .. they could have just as easily said 1kF = 1C/1V. Many things use kg instead of g. You can tie together things other than the unscaled base units. Then they are still tied together but 1F is a more reasonable amount.

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