Answer
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Work Step by Step
As shown in Figure 20-42a, in an unmagnetized piece of iron, the magnetic domains initially point in random directions.
Suppose the north pole of a strong magnet is brought nearby. Some of the domains rotate slightly to orient their south poles closer to the external north pole. This causes the unmagnetized iron to be attracted to the magnet.
By a similar argument, suppose the south pole of a strong magnet is brought nearby. Some of the domains rotate slightly to orient their north poles closer to the external south pole. This causes the unmagnetized iron to be attracted to the magnet.
We see that either pole of a magnet attracts an unmagnetized piece of iron.