# Transmission Line Power Flow

Background:

So, I recently watched Veritasium's video, "The Big Misconception About Electricity" and EEVblog's response to it.

Here is the circuit in question:

I think understand why the typical distributed element line model works for:

• Single conductor wires close together
• Coaxial cables and twisted pair cables

My analysis of what would happen when the switch is closed:

1. Bulb turns on for an instant because of inductive/capacitive coupling (energy flowing through field between one wire to the other wire).
2. Bulb dims due to inductive/capacitive transients dying off.
3. Bulb brightens depending on line impedance and reflections once the signal travels along the wire, stabilizing if the impedance is matched or when the reflection waves die off.

My questions though:

• Is my analysis correct? In part 3 especially I am confused as to whether or not the energy is flowing along, but outside the wire in an EM field (and not between the two transmission lines). If so, are there any good visualizations of this?
• How does distance between the two wires affect the transmission line analysis? For example, if the distance was (>>1) meter? My guess is that the inductive and capacitive coupling would be weaker with greater distance so there would be less current flow = less brighter bulb in part 1, and at a certain point the distributed element transmission line model would no longer apply?
• Could you reduce your question to a minimal working example; i.e., a circuit along with analysis (equations), that replicates your difficulty. Make it one question per page so that you can get focused answers.
– Syed
Commented Nov 28, 2021 at 5:45