Why are "magnetic field lines" called "lines of force" when they are actually perpendicular to direction of force (Lorentz force,cross product)?It makes sense to call "field lines" as "lines of force" in case of fields like gravitational, electrostatic, etc., but not in magnetic force it seems to me.

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Why are &quot;magnetic field lines&quot; called &quot;lines of force&quot; when they are actually perpendicular to direction of force (Lorentz force,cross product)?It makes sense to call &quot;field lines&quot; as &quot;lines of force&quot; in case of fields like gravitational, electrostatic, etc., but not in magnetic force it seems to me.

geoforoiunpwd · Accepted Answer

The gravitational force on a point mass will be along the tangent to the gravitational field line at that point. The electrostatic force will be along the direction of tangent for a positive point charge and opposite to the direction of tangent for a negative point charge of the electric field line at that particular position.In a similar way, the magnetic field lines denote the direction of magnetic force on a hypothetical magnetic charge (magnetic monopole). The direction of force is along the tangent for a positive magnetic charge (north pole) and opposite for a negative magnetic charge (south pole). This explains why the alternate term for field lines &quot;lines of force&quot; is named in that way.The Lorentz force, given by             F      →        =  q  (            v      →        ×            B      →        ) is the force exerted on a moving electric charge by a magnetic field.

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