Have you ever heard of Ugly’s Guide?
“The little yellow electrical book?”
“That little five dollar book with the electrical math in it?”
Ugly’s Guide to Electrical References is a little book, spiral comb bound, and is full of electrical formulae. All manipulations of Ohm’s Law, for example, in a chart inside, and maniuplations of the Power Formula on the front. When I’m teaching young designers and production electricians, this is a required text in introductory classes.
Pick this up at Amazon, it’s also a great stocking stuffer! I’m also adding it to my Amazon Book Store, which you get to by clicking on “RECOMMENDED READING” at the top of JimOnLight (or clicking that link right there, obviously).