02-22-2010, 12:11 AM
If you've never opened up the casing on a 9V battery you should try it. Inside are 6 little 1.5v batteries, similar to a AAA but smaller I think. This is a great demonstration of how voltage sources are additive when placed in series. 9V batteries are also cool because you can plug the + of one battery into the - of the other without any extra wire or fasterners. Given enough batteries you can add up to quite a voltage!