In article .com,
says...
Is that definition of "DC" written in stone (i.e. fundametnally true)
or as defined by convention? How is a sine wave operating as all
postive voltages not yielding a current (albeit variable) of a single
polarity, single direction that does not alternate? Isn't saying it is
an "alternating current with a dc offset" a rather queer way of saying
things since there actually is no (net) alternating (i.e.
bi-directional) current flow?
The only difference between your "DC sine wave" and an your "AC sine
wave" is where you happen to choose your reference point. Most of us
don't consider a wavefornm to magically shift from AC to DC simply by a
change of reference.

Robert