My family has moved into an 80-year-old home. How can we assess the safety of the wiring in the home? It appears that some (but not all) of the wiring was added at some point.
For example: In one bedroom, rather than opening up the plaster walls, wiring has been run to outlets through exterior conduit, while two wall-mounted lights are served by wiring run within the walls.
In another room, the polarity is "reversed" in one outlet.
In another room, a light switch connects to nothing. (Judging by it's placement, it seems that it should go to an overhead light, but there is no fixture.)
What can we do to make sure that all of the wiring is safe? And afterward, if it appears that rewiring is necessary, what is involved in rewiring a house with plaster walls?