Final answer:
To verify a compass has been swung, check that the needle aligns with magnetic field lines around a magnet or for a sundial compass, ensure it points north and the shadow indicates the correct time. For navigation, observe that the needle maintains its orientation relative to the Earth's magnetic field during travel.
Step-by-step explanation:
To verify that the compass has been properly swung, one can observe the movement of the compass needle as it aligns with a magnetic field. When moving the compass around a bar magnet, the needle will rotate and align itself with the magnetic field lines at various points around the magnet. The strength of the magnetic field can be indicated by the brightness of the magnetic field icons, but also measured using a magnetic field meter for precision. By checking the field strength at different points, one can map out the magnetic field accurately.
When referencing a compass integrated into a pocket sundial, one would verify the swing of the compass by ensuring its fin is oriented to point north. A clear indication of a successfully swung compass is when a shadow cast by the sundial aligns with its indicated time, provided that the base compass is correctly aligned with geographic north.
In regards to navigation and the Earth's magnetic field, assuming the magnetic north aligns with the geographic north, a compass in an airplane flying due west along the equator will have its needle dipole perpendicular to the direction of motion at the prime meridian. As the plane continues westward, the compass needle should maintain its orientation relative to the Earth's magnetic field.