A: pay attention to current flow and assign +/-using algebraic mathematics
A: Alternating voltages means the phase factor must be considered.
the cell will add all of the voltages to a lump sum.
add the signal voltages by connecting them in series - to +
3.5v You add the voltages when placed in series.
Of each individual dry cell, not at all. If you connect them together in series then their voltages add.
A: Those voltages are called distribution voltages to differentiate from transmission voltages. And that varies from state to state and locals . Usually around 10kv to 20 kv
Break down voltages happens at low voltages (.6 for silicon & .3 for germanium), whereas knee voltages at higher voltages. That's why its cheaper.
Digital
Cell phone voltages are DC5V-5.5V
Batteries are connected in series to add their voltages together. For example, two car batteries in series will give twenty four volts.
That is a series circuit, all parts have the same current flowing through, and the voltages add up.
Batteries placed in series (which is what you're describing) add their voltages together. Thus two 1.5 volt batteries give 3 volts in series ... IF they point in the same direction. If they point in opposite directions, you get zero volts.