Timeline for How does ground close the circuit, why isn't the current miniscule?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Mar 22, 2021 at 11:58 | vote | accept | daniel purdew | ||
| Mar 22, 2021 at 4:20 | comment | added | K H | Similarly, wood is not a great conductor, but once you add stain or varnish and coat it, your conductivity could change. The part of it touching the bottom of your feet is rather large by conductor standards, and the part of it that is thin is still minimum 5/8 thick, typically includes glue that could be more conductive, and is in contact in every other direction with a large amount of wood and metal (including G wires), all that branching out and connecting down to an immense surface of actual ground. The way it branches out gives it low inductance (which objects to fast current change). | |
| Mar 22, 2021 at 4:14 | comment | added | K H | @danielpurdew earth has low impedance between two points despite typically higher resistance per cross sectional area times length because it has immense cross sectional area. The two points are connected through the earth in a straight line, but in addition to this they are connected in parallel to each other in every other direction. This gives you a conductor with effectively infinite thickness with the caveat that each layer of thickness has some added length from having to go around the more direct conduction paths. | |
| Mar 21, 2021 at 19:29 | comment | added | Sredni Vashtar | Don't forget that AC has the unhealthy habit of going through capacitances. You might have a big series resistance, but if you are capacitively coupled to a return path in parallel to that... | |
| Mar 21, 2021 at 18:01 | comment | added | AlexVB | @danielpurdew if you stand on clean dry wooden floor you probably can touch a wire and survive. But one day it may be not so dry and 100mA is enough. | |
| Mar 21, 2021 at 17:44 | comment | added | AlexVB | I think you may neglect capacitance. It is very low with any gloves or boots. And electricians really use insulating boots and gloves when working with low (240-1000V) voltage systems. | |
| Mar 21, 2021 at 17:40 | comment | added | hacktastical | The wood floor would be an insulator, sort of. Wood resistance isn’t perfect and depends on a lot of factors, such as moisture, density, thickness, distance to source. If you also touch something metal that’s grounded, all bets are off. This is why safety grounds are used: you can’t count on the body always being insulated. | |
| Mar 21, 2021 at 17:38 | comment | added | user215805 | @daniel purdew 25ohms if we use suitable large copper conductor, whose one end is inside the earth and other connected to wire (May be your body) directly | |
| Mar 21, 2021 at 17:28 | comment | added | daniel purdew | The key detail seems to be that you are saying somehow the resistance to earth aims to be less than 25 ohms, I don't understand how this is achieved, I am standing on a wooden floor right now and I know that there are no conductive materials withing several meters of me on the floor, if I touch a live mains wire hanging from the ceiling, it has to at least go through the floor and up the walls and into the neutral wire. Is this not a lot of resistance? Do I just have no notion of the numbers involved? | |
| Mar 21, 2021 at 17:10 | history | edited | hacktastical | CC BY-SA 4.0 | added 415 characters in body |
| Mar 21, 2021 at 17:03 | history | edited | hacktastical | CC BY-SA 4.0 | added 415 characters in body |
| Mar 21, 2021 at 16:54 | history | answered | hacktastical | CC BY-SA 4.0 |