Figure 1-1. Typical magnetic head
2.
The flux density through a cross section of the magnetic circuit depends on the signal current and
the medium through which the flux is passing. Since the flux density in the gap is lower than in the
core, the flux lines spread out at the gap to form a bridging field (fig 1-2). When the magnetic tape is
placed against the head, bridging the gap, flux lines from one pole piece enter the tape and return to the
core at the other pole piece. The magnetic domains on the tape, which act like small permanent
magnets, then align themselves along the flux lines to form a magnetic pattern depending on the
direction and density of the flux lines when the tape leaves the gap. The pattern remains on the tape
because the head has no effect after the tape passes the trailing edge of the gap (fig 1-3).
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