@Rocknroller912 active pickups have less coils, which also elimnates hum, but don’t have enough current to be amplified like a passive pickup, therefor need some extra help; they have a little pre-amp stage and need a 9v battery to power…   Read more»

@mario grounding the bridge and covering cavities with shielding copper/aluminium foil or conductive paint is done to avoid hum. It has nothing to do with safety. In theory it will indeed pass the current through you, if you are touching…   Read more»