Zener Basics - Zener Diodes in AC - Forward-to-Reverse-Bias

Source: excellent video-class at https://www.youtube.com/watch?v=8GEaAU2Z0hc - Once in FB, after 0.7V the ZD will lock on 0.7V not only itself but also everything that's in parallel with it. - Remember that Vr1 = Vs - Vd