Demonstration of voltage and current ratios, and explanation of why the primary voltage increases when loads are added to the secondary.
In my "Buck-Boost Transformers" video I use the concept of relative polarity to adjust voltages up or down by connecting primary and secondary windings in either an additive (in-phase) or subtractive (out-of-phase) orientations. https://youtu.be/aOtSnJo6PfM
In my "120/240 V In-Phase or Out-of-Phase" video I address the concept of reference and how that can appear to flip one waveform relative to another. https://youtu.be/nOSYHUxHxG8
In my "Dual Voltage Windings - Part 1" video I briefly mention polarity as relates to the H1/H2/H3/H4 and X1/X2/X3/X4 labels on dual-voltage transformer leads. https://youtu.be/qIzkRWVWavQ