Magnetic Fields

The magnetic field acts only on charge that moves, through $\vec{F} = q\vec{v}\times\vec{B}$. Being a cross product, the force is perpendicular to $\vec{v}$ and to $\vec{B}$ simultaneously, with magnitude $|q|vB\sin\theta$: it is zero when the velocity lies along the field, largest when the velocity is perpendicular to it, and never aligned with the field at all. Magnetic field lines carry no ends, since $\oint\vec{B}\cdot d\vec{A} = 0$ everywhere and there is no magnetic charge for a line to start on.

Three errors dominate. Aiming the force along $\vec{B}$, imported wholesale from $\vec{F} = q\vec{E}$, which sends every later trajectory the wrong way. Giving a magnetic field a grip on a charge sitting at rest, when $v = 0$ makes the force exactly zero no matter how strong the field. And reading a field-line map as a force map, ending lines on poles as if poles were charges and then dragging a charge along a line toward one. Field lines thread through the magnet and close; their direction orients a compass, and it does not point a force.