Final answer:
The constructs associated with magnetic field lines are visual representations of the direction and strength of electromagnetic forces. Magnetic field lines align with a compass needle and their density indicates field strength, while gravity is significant in the structural formation of galaxies.
Step-by-step explanation:
The question relates to the phenomena and forces associated with magnetic fields. Magnetic field lines are a visual tool used to represent the direction and magnitude of magnetic forces, with the direction indicated by a compass needle aligning itself with the field lines and the density of these lines representing the field's strength. The correct answer to the phenomena describing the direction and magnitude of normal forces, such as the force exerted by magnetic fields on moving charges, is electromagnetic forces. Gravitational pull, on the other hand, is a force that governs the structure of galaxies and the motions of astronomical objects.
Electromagnetic forces also include both attraction and repulsion, which are dictated by the orientation and movement of electrical charges in a magnetic field. When relating to the electric field that supports the weight of a free electron near Earth's surface, the electric field's magnitude is significantly small, highlighting the relative strength of gravitational and electrostatic forces, with gravity being much weaker compared to electrostatic forces.