On engines with breaker points, what happens when the breaker points are opened?

When breaker points are opened, the primary circuit current stops flowing. This is a fundamental aspect of how traditional ignition systems operate. The breaker points are a crucial part of the ignition system in small engines, particularly those using a contact-point ignition system.

When the points close, current flows through the primary winding of the ignition coil, creating a magnetic field. Once the points open, this flow of electrical current is interrupted. The sudden interruption of current causes the magnetic field in the coil to collapse. As the magnetic field collapses, it induces a high voltage in the secondary winding of the ignition coil, which generates a spark at the spark plug, igniting the air-fuel mixture in the engine's cylinder.

This process is vital for the engine's timing and performance, but the primary focus here is on the fact that opening the points halts the current flow in the primary circuit, which is essential for generating the high voltage needed for ignition. Other options do not directly describe the immediate effect that occurs from the opening of the breaker points.