A lawnmower generates the power for the spark plug using a magneto. When the magnets fly past the U-shaped armature, they induce a magnetic field, which in turn creates a small amount of current in the primary and secondary coil. When the magnetic field in the armature reaches its maximum, a switch in the electronic control unit opens, which breaks the flow of current through the primary coil and causes a voltage spike. The secondary coil then amplifies this voltage, which is fed to the spark plug making the lawnmower work.