The "spark" you see at the points, when they open, (primary circuit is opening) is just "switch arcing" from the coil (a step up transformer) trying to maintain flow. The actual, so called, spark at the plug is a high voltage, (secondary circuit) jump across a purpose made gap. That spark is caused by the magnetic field built up in the coil rapidly collapsing, inducing a very high voltage in the coil's secondary winding. Carried down the plug wires to plug, down the plug center wire (anode) across "the gap" to grounded tab (cathode). In football it's called intentional grounding.
The points "gap" is important for timing and proper coil saturation....and keeping them "clean".
The plug gap (the arc jump distance) is important to cause optimum spark "strength" for explosion.
When you are around electrical or electronics dealing with high voltage, high amp AC.....and you are discussing operation, you NEVER point at something or it will jump to you.
Last edited by bartamos; 09/10/2025 5:41 PM. Reason: spelling/clarification
