Currents cause magnetic fields. If we say that the compass lines up along the field, then the field curls around the wire. B field lines have no beginning or end!

Permanent magnets are just collections of little current loops

In Jules Verne’s story “Journey to the Center of the Earth”, some dudes travel deep inside the Earth. If this were possible and they had a compass with them, what direction would their N compass needle point? A] toward the Earth’s northern geomagnetic pole B] toward the Earth’s southern geomagnetic pole C] it would have no preferred direction

Magnetic field lines curl around currents, forming closed loops. As such, they have no beginning and no end. What is the total flux of the magnetic field through any closed surface? Recall that A] 0 B] I enc times a positive constant C] -I enc times a positive constant

Note key differences with E fields: NO force if v=0 NO force if v is parallel to B Direction of force depends on direction of v (perp to v!)