Electronics > Beginners

Some noob questions

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Mr. Scram:

--- Quote from: Mr D on August 17, 2018, 07:40:13 am ---So if you take a 9 volt battery, attach a wire to each terminal, then hold one terminal in one hand, and the other terminal in the other hand, then your body, is it not, acting as a resistor? And the amount of current flowing through your body will determined by Ohm's law.

Now, replace your body with the earth under your feet, stick one wire in the ground, and the other wire in the ground a meter away, then the planet
Earth is also acting like a resistor?

Or is this not what is meant by "ground" in a circuit?

--- End quote ---
Have you looked at what's needed to make a properly earthed connection and why telegraph lines tend to be single wires?

There's a relevant difference between your body and Earth.

Mr D:

--- Quote from: Mr. Scram on August 17, 2018, 07:45:26 am ---Have you looked at what's needed to make a properly earthed connection and why telegraph lines tend to be single wires?

--- End quote ---

Have i looked at the answer to my question? No, and i wouldn't know where to find it. That's why i'm asking questions here.

Mr. Scram:

--- Quote from: Mr D on August 17, 2018, 07:51:53 am ---Have i looked at the answer to my question? No, and i wouldn't know where to find it. That's why i'm asking questions here.

--- End quote ---
It's generally expected you try to answer questions yourself by doing some research. The questions that you can't answer yourself or require some insight can then be asked on something like a forum. Entering "what's needed to make a properly earthed connection" in search engine immediately yields useful results, such as the link below. I'm not trying to be a hard-ass here, but you'll really learn more if you investigate yourself too and I certainly wouldn't suggest searching for something if it's impossible to find. :)

If you follow the link you'll see that a properly earthed connection is a sizeable copper rod stuck into not too dry ground deep enough. This suggests there's a conductive path to the Earth itself.



Following the telegraph hint we find a page that says the following: "There were some very good reasons that the closed circuit system was almost universally used on Morse wire circuits in the USA and Canada. Single wire, ground or earth return circuits were normally used, which had half the resistance of a metallic loop, since the earth return contributed no resistance to the circuit if it was more than a few miles in length. The only circuit resistance was due to the line wire resistance and the resistance in the instrument windings or other equipment in circuit."

Apparently, the Earth effectively doesn't have much resistance at all even when compared to a wire circuit. Now, explaining this is where the forum might help. We already established there's a relevant difference between your body and Earth. This difference is the size. You probably know that larger diameter wires have less resistance than thin wires. Even though the Earth is made up of not wonderfully conductive materials, it is massively large. This is why it ends up being a pretty good conductor. It's essentially a wire with a really, really huge diameter.

http://www.housingforhealth.com/housing-guide/electrical-earth-connection-2/
http://www.morsetelegraphclub.org/wirechief/#closed

The Soulman:
The "earthing" symbols used in the two schematics are very common (pun intended) and depict
a connection to a common conducting surface, this can be a ground plane on a pcb, or the metal frame of a car, or...

Mr D:
OK, but i'm still not much the wiser!

The earth has effectively no resistance?

So, when the current reaches the bottom left corner of the rectangle in the attached schematic, where does the current want to go? Upwards to the neg. terminal or down into the ground? Which has less resistance?

See here at 4:30:


To quote: "A circuit is a closed loop that carries electricity.....in order to have a circuit, it has to come back to where it starts from"

How is a circuit that runs a wire from the pos. terminal of a source straight down in to the ground a closed loop?





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