In a magneto, what happens when the primary points open?

When the primary points in a magneto open, the current in the primary circuit is interrupted. This interruption is a critical part of the magneto's operation, which leads to the generation of high voltage in the secondary winding.

As the current flows through the primary winding, it creates a magnetic field. When the points open, this magnetic field collapses rapidly, which induces a high voltage in the secondary coil. It's this high voltage that is essential for creating the spark at the spark plug, which ignites the fuel-air mixture in the engine's cylinders.

This process is fundamental to the functioning of magnetos in aircraft engines, where reliable ignition is crucial for engine performance. Understanding the sequence of events when the primary points open helps clarify how magnetos operate and ensures that maintenance and troubleshooting can be effectively performed.