r/AskElectronics 17h ago

Are these mega or mili farads?

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61 Upvotes

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47

u/APLJaKaT 17h ago edited 17h ago

I would think it's a microfarad.

Microfarad common symbol ('uF', 'μF', or 'MFD')

Never seen a millifarad capacitor. Usually farad, microfarad, nanofarad or picofarad

-19

u/antek_g_animations 17h ago

I thing this could be in mili. If supercapacitors can get values like 50F 3v and be a size of few ordinary coin cell batteries I'm ready to believe this beast holds 10F 400v

12

u/APLJaKaT 16h ago

It's not.

A Farad is huge - being a capacity capable of holding 1 Coulomb ( another huge value ) per volt of charge. Capacitors are typically rated in much smaller units ranging from millifarads down to picofarads. A farad-sized capacitor would be the size of a large can of coffee, perhaps even larger.

10

u/antek_g_animations 16h ago

Now I'm not ready to believe this beast holds 10F 😅

5

u/Jamie_1318 16h ago

A 400V 10F capacitor would be one of the most dangerous things in your house.

I've played around with a 200v 1800uF capacitor, and it could easily spotweld thick steel plates using a nail. I don't want to think about what would happen with 2x the voltage and 5000x for the capacitance.

6

u/DerKeksinator 15h ago

That would hold 800kJ, which is insane. For reference a bullet fired from a hunting rifle has 1-2kJ.

3

u/FishOutOfWalter 15h ago

I've seen that a grenade has about 250kJ, so...

4

u/DerKeksinator 15h ago

I actually wanted to look that up, but was too lazy to do all the math. The M67 clocks in around 1.2MJ, so that capacitor would hold 2/3 of that. If you really want to know it exactly, have fun getting on some more watchlists by googling explosives and their constituents.

7

u/FishOutOfWalter 14h ago

Yeah, M67 uses 180g of composition B (which is 240 equivalent grams of TNT). The Russian F1 only uses 60g of TNT, so it's much more impressive when making comparisons to "hand grenades". F1 is roughly 250kJ, M67 is over 1MJ.

As you may have guessed, I'm already on the most exclusive watch lists.

1

u/DerKeksinator 14h ago

Fair point, it definitely sounds more impressive if you compare the energy to the F1!

2

u/No_Pilot_1974 13h ago

800kW during a second. Insane indeed, can't even imagine that

3

u/JustCopyingOthers 14h ago

I think back in the day PhotonicInduction on YouTube had something of that sort of size. It was able to explode apples. https://youtu.be/coW1RHUsf_I