Final answer:
A magnet will never repel iron because iron is ferromagnetic and becomes locally magnetized with opposite poles when near a magnet, leading to attraction. Iron doesn't have its own permanent poles that would cause repulsion with a magnet's poles.
Step-by-step explanation:
A magnet will never repel a piece of iron because iron is a ferromagnetic material that is naturally attracted to magnets. When a magnet comes into contact with an unmagnetized piece of iron, the iron becomes locally magnetized with unlike poles closest to the magnet, causing an attractive force.
This principle is observed in ferromagnetic materials, which, unlike magnets, do not have permanent magnetic poles of their own to cause repulsion when brought near a magnet.
Moreover, when an unmagnetized piece of iron is placed between or near magnets, it can become magnetized in such a way that its induced poles align opposite to the nearest poles of the magnets around it. This results in attraction rather than repulsion. For example, if a south pole of a magnet is near the iron, the nearest part of the iron will become a north pole, therefore, attracting each other.
In essence, iron enhances the magnetic field of a magnet by aligning its domains in a way that strengthens the attraction. It doesn't possess intrinsic poles that oppose the magnet's poles, which is why there is no scenario in which a magnet would repel a piece of iron.