Wavetrader - as far as I know electrons don't flow. Electric current is an electromagnetic wave (while electrons move only about 1/2" per second) which is also difficult to explain using example od stacked balls since space between electrons is in order of 100000 time their size. One theory says that electrons emit photons but this doesn't add up if we assume that photons can move in any direction. It is probably better explained here:
http://www.geocities.com/natureoflight/pg4.html
http://www.geocities.com/natureoflight/pg4.html