Some students were performing an experiment involving 2 solenoids in a line, a power source attached to the primary, and a globe attached to the secondary solenoid. A crude depiction of the setup is as below. /////// /////// <---- Rod inserted here Pri . . . Sec An iron rod was inserted through both solenoids and the globe became exceptionally bright when the iron rod was fully through the secondary and half way into the primary. This effect was persistent, not temporary, or fluctuating. I cannot figure out why, any help would be appreciated.