Final answer:
In the internal timing of a magneto, the breaker points open just as the magnet poles pass the neutral plane. This timing critical for generating the correct spark for engine ignition, relying on the principles of magnetic field interactions with a coil as the magnet spins by.
Step-by-step explanation:
When internally timing a magneto, the breaker points begin to open when the magnet poles are a few degrees beyond the neutral plane.
A magneto is a type of electrical generator that uses the motion of a magnet near a coil to induce an electric current. As the magnet spins, the changing magnetic field induces a current in the wire coil.
At a certain point in the rotation, the current reaches a level where it can create a spark large enough to ignite fuel in an engine.
This occurs at the precise moment when the breaker points start to open, which is ideally timed to the position of the magnet a few degrees past the neutral plane, where the magnetic flux through the coil changes direction.
The magnetic field outside a magnet points away from the north pole and towards the south pole (Figure 20.9).
During the timing of a magneto, this understanding of the magnetic field is utilized to precisely control the ignition timing for efficient engine operation.