A) Power (P) equals voltage (E) multiplied by current (I)
There is a really excellent method for memorizing the various power/voltage/current relationships called simply the "PIE" method or also the "Power Triangle".
|NJ2X PIE chart for finding the relation between power, current, and voltage|
To use this, memorize drawing a triangle with the letter PIE arranged as above which stand for Power (P), Current (I), and Voltage (E) . Then cover any letter to find the formula (see above). Presto magico - easy as PIE!