BergeronDemo

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A travelling-wave (Bergeron) transmission line showing how a step propagates and reflects.

A 100 V step is applied at the sending end $V_s$ of a distributed (Bergeron) line; after the line's propagation delay it arrives at the receiving end $V_r$, where a selectable termination (50 / 100 / 200 Ω) sets how much reflects back.

A source energizes a distributed-parameter line through a switch. Because the line has a finite propagation delay, the disturbance travels from one end to the other and reflects off the terminations instead of appearing everywhere at once. The deliberately short time window captures those reflections, while the text readouts and plot track the terminal voltages.

This is the one sample where distance matters: a lumped R-L-C changes everywhere at once, but a distributed line carries the 100 V step as a wave that needs real time to cross. When the wave hits V_r, the fraction that reflects is set by how far the termination is from the line's characteristic impedance Zc — a matched load swallows it cleanly, while 50 Ω or 200 Ω bounce part of it back to re-reflect at the source. Flip the selector between the three resistors and watch the staircase of reflections change. Because the transit time is tiny, the run uses a very short window so those bounces do not blur together — the travelling-wave story behind the EMT course's line models.