I've always been bemused by EE wallet cards that contain:
V = IR
I = V/R
R = V/I
If an EE does not know this formulas, he isn't an EE. If he understands so little about algebra that he needs the three forms, he's going to be misusing the formula.
Guess like all engineering jobs, sometimes your job is so far from practice and so involved in regulations, meetings, standards, bureaucracy, reports, a little refcard with the most basic things can help to quickly reset your brain for the rare occasion where you need to actually do something.
As a hobbyist and a complete beginner, you can do surprising amount of stuff just by memorizing U=RI and P=UI. Through a closed loop current is always the same. Through a closed loop voltage drops must equal the voltage source.
