Final answer:
Magnetic field lines are a useful tool for visualizing the strength and direction of magnetic fields, with the spacing of lines indicating field strength and the use of a compass or iron filings revealing the field's properties.
Step-by-step explanation:
The magnetic field lines model is helpful because it provides a visual representation of the strength and direction of magnetic fields. This model uses the properties of magnetic field lines, which include the rule that the direction of the magnetic field is tangent to the field line at any point, and the density of magnetic field lines indicates the strength of the field. Tools such as a compass, which points in the direction of the field lines, or iron filings, which align along the field lines, enable the mapping of the magnetic field around a magnet revealing its invisible properties.
In areas where the magnetic field is stronger, the field lines are represented as being closer together, while in weaker field areas, they are further apart. The closeness of lines indicates the intensity or strength of the field. Moreover, the concept of magnetic flux is used as a measure of the field's strength through a given surface, with a higher number of lines crossing a surface indicating greater flux and a stronger field.