Why do two 2V batteries in parallel have 2V while in series they produce 4V?

[Drizzy]

Homework Statement

Can somebody help me understand why two 2V parallell batteries weill have the total voltage of 2 while two 2V batteries in series will have the total voltage of 4V? Is there a good analogy to help me understand?

Homework Equations

The Attempt at a Solution

 

[gneill]

Make an analogy with gravitational potential energy. Near the surface of the Earth it depends upon vertical height. Take two vertical sticks of the same length. In parallel their tops have the same height (are at the same potential). Now put them in series. What's the potential at the top of the upper stick?