The voltage from terminal 2 to terminal 1 drops to 20V, that is, the voltage is 20V when terminal 2 is+and terminal 1 is-,so the voltage is-20v when terminal 2 is-and terminal 1 is+; 4A current enters terminal 2, so the current flowing out of terminal 1 is 4A, so the current flowing into terminal 1 is-4A; Accordingly, (1) Q: a:v=-20V, I =-4A；; b:v=-20V，I = 4A； c:v=20V，I =-4A； d:v=20V，I = 4A； (2) Q: No matter how the reference direction is chosen, the actual power of the component is constant; Take A as an example: p=vi=80W, because vi is the relevant reference direction, the absorbed power of the element is 80W; If bcd is used to calculate the supplied power of -80W, it is actually the absorbed power of 80W, and the actual power is the same.