"Cecil Moore" wrote in message
...
Yes, but those steady-state shortcuts often lead to a distorted
view of reality. Exactly what magic happens at the instant when a
system goes from the transient state to steady-state?

there is no magic, and real systems can never get to steady state. the
steady state approximations are used by engineers who understand their
limitations and know when they can apply them to easily get answers that are
good enough for every day use. engineers who don't understand them can
always use the full field equations and calculate the exact answers if they
have the time and enough information about the system... but they will never
be able to answer the question about forward and reflected power except at a
specific instant in time and single location in the system as the transients
never go away and power in is never equal to power out except by
coincidence.