Why outlets spark when unplugging - EMF & Inductors

Almost every typical gasoline spark-ignition engine in cars still uses traditional "IDI" (Inductive Discharge Ignition) high-inductance Coils with the HV generated by transforming up the voltage spike of the back-EMF pulse. So you basicly "turn off" the coil to make the spark. The saturation level of the laminated Iron core is what sets the energy amount of the spark. The difference beeing more modern materials, and using IGBT's instead of breakerpoints and capacitors. Some cars tho (a bit rare) and smaller or very high rpm engines (quite often) uses "CDI" (Capacitor Discharge Ignition) Where IGBT's or Thyristors are used to dump 400V (or so) directly into the primary winding of a special low-inductance coil ("pulse-transformer") without using back-EMF (there hardly is any back-EMF either due to the low inductance).