(1) When you plug a passive pickup into a guitar amp, does the amplifier send power into the guitar's circuit? Or is it just a one-way signal flow from the guitar to the amp? no
(2) What kind of power is flowing inside a guitar circuit between the pickups, pots and output jack? There must be some level of low-wattage electricity. Is the electricity generated by the magnetics in the pickup? Is there still power flowing in the guitar's circuit even when the guitar is not plugged in (assuming it's a complete circuit)? the strings vibration over the pickups creates the power, the amp boosts that so you can hear it.
(5) Is the signal coming out of the guitar before amplification considered line-level? no
(11) When I look at the internals of an amp, the wiring consists of little, thin wires and circuit boards up until the actual amplification. After amplification, I begin to see thick, beefier wires. What is the difference between pre-amp and post-amp wiring? Just a larger gauge/thickness of wire?
(12) Why is a larger wire necessary after amplification?
(13) How do you know what type of wire you need? Is there only pre-amp and post-amp wire types? you can use any, just make sure its thick enough for the amount of voltage going through it, or it will be like fuse wire.
(14) Why is only copper wire used in guitars/amps? its not, aluminium, silver wire can be used
(15) What happens if you accidentally touch the live wires inside of a guitar while it is plugged into an amp? Will it zap you? no
(16) If you temporarily short the circuit inside a guitar, can you ruin some of the electronics? no, thats how kill switches work
(17) What about post-amplification wires? I have an amp that outputs 120 watts @ 8 ohms. Is that enough to zap you if you accidentally touch the live wire? speakers can give you a shock if they are high voltage, ive not had one from a guitar amp.
(18) Can you ruin the amp if you temporarily short circuit the wires? very possible if you mess with the internals.