Batteries - cont.
1. The 9 volt battery supplies 9 volts. The AAA battery supplies 1.5 volts.
2. Both the AAA battery and the D battery supply the same 1.5 volts. Since the D battery is physically bigger, though, it has more chemicals in it that can supply more energy - it can push (lift up) MORE charge through 1.5 volts than the AAA battery can.