Keith Dysart wrote:
Please describe the final state of the step
excited open circuited line using photons.

Photons are emitted and absorbed by the electrons
as the electrons lose/gain energy. Photons are not
conserved. Only the energy in photons is conserved.

In a DC system with no accelerating or decelerating
electrons, all of the photons have been absorbed
back into the electrons (or lost to radiation).
Of course, this describes an ideal system.
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73, Cecil http://www.w5dxp.com