Think high school science. If you have a coil of single
conductor wire and you connect a
voltage source across the ends,
current will
pass through the
wire. The
current flowing in the circular
pattern creates an electromagnetic force in the direction of the axis of the coil (in this case, the
batten pipe). Any magnetic material placed inside this coil will "feel" the magnetic force. This force is not enough cause the coil to shoot off the
batten pipe, but will cause heating in the pipe(induction). In the case of SO cable, you have
current flowing from the source to the load via the hot
wire and retuning via the
neutral. Since both of these wires are in the same cable, they both have the same path. The opposite directions of
current flow in the hot and the
neutral cause the electromagnetic force due to the
current flows to cancel each other out. Therefore no inductive heating in the pipe.