Physics 2 returns with a vengence

I was hoping I could avoid this part but it looks like I will have to read a lot of e&m physics to really make a guitar from scratch. I know I could possibly just buy one, but I really don't want to put much money into this yet, and I don't know that I could find a guitar I could physically play. So I may be writing a bit less often for a bit while I finish learning the physics I never quite mastered a decade ago. I don't want to buy pickups, cause they are expensive and I would like to understand them better. Plus, I don't know yet if in making my mandolin electric and tuning it with each string different, so 8 strings instead of four, if a standard pickup would even work best. I am enough of a nerd that making my first set of pickups would be satisfying, even if I wind up buying some later when I can actually play well enough to need them. I will have to figure out a neck design too, that allows me access to the strings while maintaining their tension and allowing multiple pickups. And I still don't quite get the part about how the sound gets out of the guitar. Stupid, I know, but perhaps understandable since I have no electric guitar to play with. If they are hooked up to an amp, is there a cord? Where is the amp? How big is it? When Brian is playing with three amps, is there a cord running from his guitar to the amps? Then how could he walk around onstage playing his guitar? I hope in a day or two this confusion will seem silly and I will understand completely.