Hmm, I have wondered about this too and I thought of an explanation that might work. Think about this, the electrons in the main branch tries to move forward and when it comes to the split point, the electrons in the wire will exert an equal force to the electrons in each parallel circuit. So...
Here is the link http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html Scroll down to osmosis. I just don't understand how water can move to the other side.
Let's say there are two parts in a container, one part is pure water and the other part is some solution. There is a membrane blocking the solution particles from moving to the other side. So eventually, water will be pulled to the solution side to make it less concentrated.
My question is...