A magnetic field can be defined as the region around a magnet or a current-carrying wire where its influence can be felt. It is an invisible force that can exert a magnetic force on other magnetic objects within its vicinity.

Magnetic field lines are used to represent the direction and strength of the magnetic fields. They always extend from the north pole of a magnet to its south pole, forming closed loops. The density of these lines reflects the strength of the magnetic field, with lines closer together indicating a stronger field. Understanding magnetic field lines is crucial for visualizing and analyzing the behavior of magnetic fields.

Magnetic fields interact with magnetic objects, such as magnets or ferromagnetic materials like iron. When in the influence of a magnetic field, these objects can experience various effects, such as attraction or repulsion. For instance, opposite poles of magnets attract each other, while like poles repel. This behavior is due to the alignment of magnetic moments within the objects in response to the magnetic field.

To illustrate this, let's consider a simple example. Take two bar magnets and bring their opposite poles close to each other. You'll notice that they attract each other, indicating the presence of magnetic fields. Similarly, if you bring the like poles of the magnets close, you'll feel a repulsive force between them.