Hmm. Some of the explanations went over my head but this seems to make sense:
Electricity needs a loop because the electrons need to go somewhere after giving up their energy.
Just your water pipe idea, where a pump returns the water to the top flow down again, the electrons return to a battery, say, to be re-charged flow again.
So the electrons aren't exiting the system, they're just all losing their charge and returning back to Ground to get recharged and go for round 2.
You don't mean charge in the second paragraph, all electrons have the same charge all the time.
The energy is a function of the whole system, not just the electron, in fact the energy resides in the electric field as
In all everyday situations the positive charges and negative charges balance out to dozens of orders of magnitude,
as the energy to separate significant amounts of charge is astronomical.
In a metal wire the positive charges are fixed, they are the metal atoms (whose electrons have wandered off),
and the electrons are mobile, but they stay with the metal to balance out the charge.
When they move en-masse in the same direction you have a macroscopic observable current - the negative
charges move, the positive ones stay still, net flow of charge (but stays balanced). You cannot have all
the electrons marching out of the metal into the air and building up an imbalance, except in miniscule amounts
(a millionth of percent imbalance would generate a potential in the millions to billions of volts, something
So the circuit has to be closed, the mobile charges stay in close association with an equal number of fixed
charges (in semiconductors and ionic solutions the charge carriers can be of either charge polarity).