this post was submitted on 03 Oct 2024
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chapotraphouse

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[–] [email protected] 33 points 4 weeks ago (7 children)

I feel like such a shitty engineer for not remembering or having the slightest interest in even the most basic electrical shit. i don’t even get this fucking meme.

I can do civil/mech/chem but show me electricity and I feel like I’m in preschool.

Pre 18th century ass brain capacity

[–] [email protected] 29 points 4 weeks ago* (last edited 4 weeks ago) (3 children)

North America uses 120 V for most circuits. Power is the product of voltage and current.

At 1 Amp, 120 watts are dissipated by the circuit. About the heat of two incandescent light bulbs.

At 10 Amps, 1200 watts are dissipated by the circuit, about the heat of a space heater.

At 551 Amps, 66,000 watts are dissipated by the circuit. I don't even have a good comparison. That's like the power draw of 50 homes all at once.

The higher the gauge, the lower the diameter of the wire. The lower the diameter of the wire, the more of that 66,000 watts is going to be dissipated by the wire itself instead of the load where it is desired. At 22 gauge, basically all of it will be dissipated by the wire, at least for the first fraction of a second before the wire vaporizes in a small explosion.

EDIT: In this scenario, the total resistance of the circuit must be at most 0.22 Ω. Otherwise, the current will not reach 551 A due to Ohm's Law, V=I×R. This resistance corresponds to a maximum length of 13 feet for copper wire and no load.

[–] [email protected] 19 points 4 weeks ago (1 children)

That’s like the power draw of 50 homes all at once.

So the average crypto mining rig?

[–] [email protected] 11 points 4 weeks ago

about $75k of mining rigs actually. 66kW is a lot of heat to dissipate

[–] [email protected] 8 points 4 weeks ago (1 children)

By dissipated by the wire instead of the load what do you mean?

[–] [email protected] 18 points 4 weeks ago (1 children)

The wire heats up.

Wires have a small resistance which causes a voltage drop over the wire if the current is big enough (U=RI), and therefore it draws power (P=UI) which warms it up. Thinner wires have more resistance.

[–] [email protected] 9 points 4 weeks ago

The rebel alliance was famously all thin wires

[–] [email protected] 3 points 4 weeks ago

I ran this by my brother who’s an electrician and he inferred that might be where the number is coming from, some data on how many amps you can dump into various wire gauges before they simply stop being solids.

[–] [email protected] 26 points 4 weeks ago

551 amps is an amount you would put in a comedic joke about using way too many amps

[–] [email protected] 19 points 4 weeks ago (1 children)

imagine trying to direct the output of a fire hose on full blast through one of those thin red drinking straws that come with cocktails

[–] [email protected] 5 points 4 weeks ago (1 children)

Isn't that pretty much how a CNC machine works?

[–] [email protected] 5 points 4 weeks ago

sort of but if we're extending the analogy i don't think the thin plastic drinking straw will make an effective replacement for the steel nozzle at the end of a water jet cutter, either

[–] [email protected] 12 points 4 weeks ago

551 amps will vaporize the wire and cause Fun for all involved.

[–] [email protected] 10 points 4 weeks ago

0.2 amps of current going through a human torso is fatal in virtually all cases.

[–] [email protected] 4 points 4 weeks ago

Yeah, it took me a few minutes to realize "551 amps? that's an insane cartoonish number", also in the engineering field, but not electrical stuff