A magnetic field is a physical vector field that describes the magnetic force per unit pole of a point. These fields are fundamentally generated by moving electric charges, which can take the form of electric currents within conductors, or by the inherent properties of certain materials. The relationship between electric and magnetic fields is central to electromagnetism, where changing electric fields can produce magnetic fields, and vice versa. Quantitatively, the field strength is measured at every point in space, and the concept of magnetic flux describes the amount of magnetic field passing through a given area. These forces govern countless natural phenomena, including the operation of electric motors and the shielding effect observed in planetary magnetospheres.