How many volts go through the white wire when hooked up right?
depends on what the source voltage is. Also depends on if the white wire is actually being used as a neutral and not hooked up as a hot wire. Electrons don't care what color the insulation is on a wire.
If you are talking about a typical and properly wired electrical circuit in a house, the black is the hot wire, the white is the neutral and the bare copper wire is the ground.
The current in such a circuit is alternating. The white wire will have the same voltage as the black wire if the circuit is currently powering a load (lamp, etc.), but not at the same time. (The current will change directions in each wire according to the cycles of the current source.)
If a second white wire is used (necessary for a 3-way switch to operate), the end of the white wire is required to be painted black.