When chopping off a DC current on its way to a load, what happens to the travelling pulse?
The source does not know that there is a load until the pulse has reached it and its effects have backpropagated to it. So the answer to your question is the same as to the question &quot;what happens if I attach a generator to a transmission line open at the far end?&quot;.
This is standard transmission line theory.
Your generator won't even know that there once was a load at the far end.