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Electric potential and earth/ground

by fletch-j
Tags: earth, electricity, ground, potential, volt
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fletch-j
#1
May6-12, 05:28 AM
P: 18
I was just wondering if the following is true/possible:

- Could a circuit be made that is connected from a terminal on one battery, through a load, and then connected to the opposite terminal of another battery, where the batteries aren't touching?
I believe it isn't possible, but would someone be able to give a quick explanation as to why this doesn't work?

Also:
- What role does an 'earthing' or 'grounding' have in a circuit where there is an power source and then a return path to the source as well as a grounding?

- On that note, could someone please clear up exactly how circuits with a grounding in them work in general?
Circuits like this seem to defy the notion that "a circuit must be closed for current to flow"


Thanks!
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fletch-j
#2
May6-12, 05:30 AM
P: 18
This is an example of a circuit that I'm talking about 'denying the notion that "a circuit must be closed for current to flow"'
upload.wikimedia.org/wikipedia/commons/d/db/Resistive_divider.png
Infinitum
#3
May6-12, 05:39 AM
P: 854
Quote Quote by fletch-j View Post
I was just wondering if the following is true/possible:

- Could a circuit be made that is connected from a terminal on one battery, through a load, and then connected to the opposite terminal of another battery, where the batteries aren't touching?
I believe it isn't possible, but would someone be able to give a quick explanation as to why this doesn't work?
Yes, its not possible, unless there is some excellent conducting medium between the batteries for the flow of electrons.

To set up a potential difference in a battery, it requires a continuous flow of charge. Now if two separate batteries are connected to the load, the electrons from the first battery have no where to go and complete their loop, and are basically just stuck. So, no current.

As for grounding,
http://en.wikipedia.org/wiki/Ground_(electricity)
http://electronics.howstuffworks.com...uestion110.htm

Earth here acts as a -huge- conductor(reserve) of electrons, so the circuit is complete.

fletch-j
#4
May6-12, 06:03 AM
P: 18
Electric potential and earth/ground

Quote Quote by Infinitum View Post
Yes, its not possible, unless there is some excellent conducting medium between the batteries for the flow of electrons.
Wait.. So you're saying it is possible? I thought it would be fundamentally impossible...
Fill me in...

To set up a potential difference in a battery, it requires a continuous flow of charge. Now if two separate batteries are connected to the load, the electrons from the first battery have no where to go and complete their loop, and are basically just stuck. So, no current.
This is what confuses me about grounding, it seems as if they cannot complete their loop. Could you elaborate a bit?
Infinitum
#5
May6-12, 06:11 AM
P: 854
Quote Quote by fletch-j View Post
Wait.. So you're saying it is possible? I thought it would be fundamentally impossible...
Fill me in...
It is possible IF you get a way to transfer electrons between the two batteries. That is by a wire, or a medium like aqueous sodium chloride, etc. This is equivalent to just touching the two batteries. Only difference being that you dont physically touch them, you just give them a way of transferring their electrons.

This is what confuses me about grounding, it seems as if they cannot complete their loop. Could you elaborate a bit?
As I said in my above post, the earth acts as the conductor/reserve of electrons. So electrons from the source can go to and through the earth, just as if it were a wire. Or, if used as a lightening conductor, earth acts as a reserve (though in the broader sense, a conductor) and takes in all the electrons.
fletch-j
#6
May6-12, 06:15 AM
P: 18
Quote Quote by Infinitum View Post
As I said in my above post, the earth acts as the conductor/reserve of electrons. So electrons from the source can go to and through the earth, just as if it were a wire. Or, if used as a lightening conductor, earth acts as a reserve (though in the broader sense, a conductor) and takes in all the electrons.
Ok, so are you saying the electrons just don't return to the power source?
Could you set up a circuit that goes :
[negative terminal of battery] --- [Load] --- [earth]
Infinitum
#7
May6-12, 06:21 AM
P: 854
Quote Quote by fletch-j View Post
Ok, so are you saying the electrons just don't return to the power source?
Could you set up a circuit that goes :
[negative terminal of battery] --- [Load] --- [earth]
Oh no. Not at all. I was just reasoning why grounding works. The lightening conductor case is irrelevant.

From wikipedia
In electronic circuit theory, a "ground" is usually idealized as an infinite source or sink for charge, which can absorb an unlimited amount of current without changing its potential.
The use of the term ground (or earth) is so common in electrical and electronics applications that circuits in portable electronic devices such as cell phones and media players as well as circuits in vehicles such as ships, aircraft, and spacecraft may be spoken of as having a "ground" connection without any actual connection to the Earth. This is usually a large conductor attached to one side of the power supply (such as the "ground plane" on a printed circuit board) which serves as the common return path for current from many different components in the circuit.
So yes, you do have to return to the power source. The grounding is just the way for it to happen.
fletch-j
#8
May6-12, 06:38 AM
P: 18
Ohhh okay!
That clears things up. I was making it too complicated for myself...
Thanks for your patience :P
Have a nice day/night (depending on where you are in the world)
Infinitum
#9
May6-12, 06:43 AM
P: 854
My pleasure

Have a good *insert time of the day here* too.


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