Why does current should returned to its source eventually?

Thread Starter

Dong-gyu Jang

Joined Jun 26, 2015
115
Hello.

I know it maybe very obvious and stupid question but...I've never thought this seriously before and I have to clear this question at least once in my life:)

We know that current flowing out of + terminal of power source go through all the allowed path of the circuit and eventually returned to - terminal of the source. I feel it is obvious but failed to give its clear reason to my friend when he asked me.

Why does current have to return to the terminal opposite to its staring terminal in power source? What happen if current leaks to other and never return?
 

Robin66

Joined Jan 5, 2016
266
This is a physics question. For metallic conduction, when an electron leaves the cathode (-ve) of a cell, the total cell will have a net positive charge, so the electron is attracted back to the cell, but preferentially the side of the cell with a deficit of electrons (the anode, +ve) rather than the cathode. Likewise, if an electron was ever to leave a circuit, then the whole circuit would be positively charged relative to its surroundings. This reduces the chances of any further electron loss. Charge is routinely moved between objects but the tendency is for equilibrium to be restored.
 

BR-549

Joined Sep 22, 2013
4,938
It's because of confinement. We limit and restrict where the free electrons can go. We do this with a voltage potential and a restricted path, thereby controlling where the electrons can go.

The whole idea of a circuit, is to prevent "leaks".
 

crutschow

Joined Mar 14, 2008
25,269
Each electron is part of an atom to balance the positive proton charge in its nucleus even though they are free to move from atom to atom in a conductor (which they aren't in an insulator). How free they are to move determines the conductor resistance.
So if an electron tries to flee the conductor there will be a net positive charge left pulling it back.
The more electrons that would leave the greater the positive charge pulling them back.
Since, in normal operation, there's nothing to pull the electron from the conductor against this positive charge, they all stay in the conductor in their flow from the negative to positive terminals of a supply.
 

GopherT

Joined Nov 23, 2012
8,012
It's because of confinement. We limit and restrict where the free electrons can go. We do this with a voltage potential and a restricted path, thereby controlling where the electrons can go.

The whole idea of a circuit, is to prevent "leaks".

This is a really bad explanation. If the whole idea of a circuit was to prevent leaks, we would not need the copper, just some hollow insulators that the electrons could flow through. Since circuits work just fine with bare wire (assuming they are not shorting out to create an undesired connection), then there is no leaking like an old hose with dry rot.

But, then again, I am sure you will create some non-applicable quantum effect nano-scale explanation to justify such a reduculous statement that will have nothing to do with the base question of the OP - so, go on, confuse the situation to your desire.
 

Thread Starter

Dong-gyu Jang

Joined Jun 26, 2015
115
I see, so the essence behind of that current must return to its source (reaching terminal opposite to departing terminal) is charge balancing. If ever one electron leaves the circuit of observation, the circuit itself becomes positive-charged so it attracts electron form outside so charge balance is immediately restored. It means charge is not leaving the circuit and charge must be returned to its source.

Yes, satisfying both allowing charge flow and charge balancing in circuit is to have current return.
 
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