Final answer:
Moving the armature allows for adjusting the magnetic field strength on it, which changes the sensitivity of magnetic flux overload devices for different triggering levels.
Step-by-step explanation:
The ability to move the armature closer or farther away from the electromagnet coil allows for adjusting the sensitivity of magnetic flux overload devices. By changing the position of the armature relative to the coil, the strength of the magnetic field that the armature experiences can be varied. This adjustability allows the device to be calibrated for different operating conditions or to trigger at different levels of magnetic flux, providing a form of control over the point at which the device will activate to protect electrical systems from excess current.