Launch Current-Power Cross-Scan - Electromagnetic Transmission Lines: Signal Propagation and Reflections Step by Step

Launched current and power are scanned across voltage and impedance. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Characteristic impedance sets launched current

The launched current is not a free label. It is the step voltage divided by the line impedance.

I=V/Z=12\ \text{V}/4\ \Omega=3\ \text{A}

Larger launched step raises current and power

Line impedance is fixed in these rows. Current rises directly, and power follows voltage times current.

\begin{array}{c|c|c|c}V&Z&I&P\\8\ \text{V}&4\ \Omega&2\ \text{A}&16\ \text{W}\\12\ \text{V}&4\ \Omega&3\ \text{A}&36\ \text{W}\\16\ \text{V}&4\ \Omega&4\ \text{A}&64\ \text{W}\\\end{array}

Larger impedance lowers current at the same step

The voltage is fixed here. The current column falls as the characteristic impedance increases.

\begin{array}{c|c|c|c}V&Z&I&P\\12\ \text{V}&3\ \Omega&4\ \text{A}&48\ \text{W}\\12\ \text{V}&4\ \Omega&3\ \text{A}&36\ \text{W}\\12\ \text{V}&6\ \Omega&2\ \text{A}&24\ \text{W}\\\end{array}