Flux density$^{OPEN}$ CL OSED OPEN CL OSED OPEN CL OSED OPEN CL OSED OPEN CL OSED Neutral Neutral Neutral Neutral 0° 90° 180° 270° 360° Static flux Resultant flux Static flux curve A Primary current C Resultant flux D Breaker timing point  opening before neutral  closing interval point  closing E-gap B Figure 4-7.  Magneto flux curves.  As the magnet rotor is turned toward the neutral position,  the amount of flux through the core starts to decrease.  [Figure 4-7D]  This change in flux linkages induces a current  in the primary winding.  [Figure 4-7C]  This induced current  creates a magnetic field of its own that opposes the change of  flux linkages inducing the current. Without current flowing in  the primary coil, the flux in the coil core decreases to zero as  the magnet rotor turns to neutral and starts to increase in the  opposite direction (dotted static flux curve in  Figure 4-7D ).  But, the electromagnetic action of the primary current  prevents the flux from changing and temporarily holds the  field instead of allowing it to change (resultant flux line in  Figure 4-7D ). They continue to occur until the voltage becomes too low  to maintain the discharge. Current flows in the secondary  winding during the time that it takes for the spark to  completely discharge. The energy or stress in the magnetic  circuit is completely dissipated by the time the contacts close  for the production of the next spark. Breaker assemblies, used  in high-tension magneto-ignition systems, automatically open  and close the primary circuit at the proper time in relation  to piston position in the cylinder to which an ignition spark  is being furnished. The interruption of the primary current  flow is accomplished through a pair of breaker contact points  made of an alloy that resists pitting and burning. Most breaker points used in aircraft ignition systems are  of the pivotless type in which one of the breaker points is  movable and the other stationary.  [Figure 4-8]  The movable  breaker point attached to the leaf spring is insulated from  the magneto housing and is connected to the primary coil.  [Figure 4-8]  The stationary breaker point is grounded to the  magneto housing to complete the primary circuit when the  points are closed and can be adjusted so that the points can  open at the proper time. As a result of the holding process, there is a very high stress in  the magnetic circuit by the time the magnet rotor has reached  the position where the breaker points are about to open. The  breaker points, when opened, function with the condenser to  interrupt the flow of current in the primary coil, causing an  extremely rapid change in flux linkages. The high-voltage in  the secondary winding discharges across the gap in the spark  plug to ignite the fuel/air mixture in the engine cylinder. Each  spark actually consists of one peak discharge, after which a  series of small oscillations takes place.  4-5