Forces on magnetically shielded conductors

The results of some simple experiments are given to show how the magntic force, acting upon a current-carrying conductor in a magnetic field, is affected as the conductor is shielded by surrounding it by a permeable shield. It is shown that the force on the conductor practically disappears if it is put inside of an iron pipe, but that the pipe experiences a force — the sum of the force in the pipe and that in the conductor being the same as that in the unshielded conductor. The idea is extended to the conductors in a slotted armature. It is shown that as the conductor is placed more deeply in the slot the force diminishes to a minimum and then experiences a slight rise at the bottom of the slot.