Owen Duffy wrote:
"In the same vein, I saw an assertion without sufficient qualification
that in a transmission line, 50% of the energy is stored/contained in
the electric field and 50% in the magnetic field. Again, general
statements from specified cases."

Now we accept that energy travels a guided path as an EM wave. The
electric and magnetic fields of a wave alternately contain the energy of
the wave. When the electric-field is at its maximum, the magnetic-field
is at its minimum, and vice versa.

The change in one field induces the other field and vice versa. Thus it
is the same energy which is being passed back and forth between both
fields. Therefore, over a prolonged period, 50% resides in each field.

Best regards, Richard Harrison, KB5WZI