[dghughes]

I'm surprised electronics work on the earth.

Such fragile things it's amazing how little it takes to destroy a device. And how much energy can be put through the same fragile device.

And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons.

A recent artie I read spoke about the reaction wheels of old spacecraft failing. Solar flares caused arcing in the metal ball bearings the would pit the bearing race. So if a steel ball bearing can't take it imagine fragile electronic devices.

[creato]

> And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons.

To have any meaning, you also need to consider the distance between the points. Any two charged points can repel each other with a force of one million tons given a particular distance.

[dghughes]

I looked up the example and it's mentions the two objects are separated by one meter.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.h...

[bovine3dom]

> And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons.

Coulombs and therefore their related units such as Farads are famous in Physics for being far too large, so this is not particularly surprising (assuming a sane distance). The capacitance of the largest capacitor bank in the world is about 0.2 Farads [1].

[1] https://www.quora.com/How-many-Farads-does-the-largest-capac...

[photojosh]

This is a 1.0 F capacitor [0], we use similar ones for short-term UPS backup so our embedded systems can shut down safely.

And a Coulomb is one amp for one second, that's not exactly large either.

So it's not that coulombs and amps are too large a unit, it's that it's hard to convert and store large amounts of energy.

[0] https://au.rs-online.com/web/p/products/7898012/

[bovine3dom]

> hard to convert and store large amounts of energy.

Which I would say means that it's a bad unit. How about an amp for a nanosecond? That would lead to much more sensible numbers elsewhere.

[ericpauley]

Keep in mind that capacitance and capacity are not the same. Case in point, the capacitor mentioned can hold a peak voltage of 24kV, which is allows for a million times more energy to be stored than the same capacitance at 24V peak. Capacitors with far lower peak voltages can have capacitance exceeding several Farads.

[bovine3dom]

Yeah, I was taking some liberties with the definition of largest.

They're still a ridiculously big unit though. Generally the biggest man-made structures on Earth are measured in mega*. Single digits are usually used for things that are roughly apple-sized.

[photojosh]

But in electricity/electronics, we deal with the entire range of metric prefixes… terabytes, nanofarads, gigaohms, microseconds.

I'm curious as to what you mean by "biggest man-made structures" though. For me that brings to mind tall buildings, long walls and big dams. I suppose that the Great Wall is 20 "megametres" long, but normally long dimensions will be in kilometres, heights are in 100s of metres and dams are in billions of cubic metres. Care to share some examples?

[bovine3dom]

> But in electricity/electronics, we deal with the entire range of metric prefixes… terabytes, nanofarads, gigaohms, microseconds

But you don't. You'll almost never use whole Farads, for example. It's even on the Wikipedia page: related units, nF, uF.

> Care to share some examples?

I don't really mind the difference between giga/mega/kilo. I was really just talking about a ballpark where we don't want the biggest thing ever to be unity in our everyday unit.

You do raise a valid point with height. This is because the gravitational field in some sense makes length directional: 3km up is very different to 3km along. Clearly, we need some vector based measures so we could scale them sensibly, g-hat and x-hat : ).

Can you think of many man made structures who have just one of some extensive property in an everyday unit?

[sandworm101]

I read that article too and am skeptical. There is a less-than-perfect correlation between space weather an wheel friction increases, but these are not exposed bearings on the outside of spacecraft. These are deep inside, behind layers of metal parts. I don't see the mechanism for creating the imbalance of charges necessary to arc inside the bearings. If it is happening, I would expect this to be far more common in terrestrial bearings. Cars build up static charges. We aren't seeing their bearings degrading so suddenly when after they drive through lighting storms or other static charge imbalances.

[StavrosK]

You're looking at it the wrong way. Electronics work on earth by definition, as that's where we want them to work. You can be surprised that electronics can be made so fragile and still work on earth, but being surprised they work is begging the question.