20.1.2—A magnetic field by field lines

Magnetic field lines show the direction a north test pole would move and use spacing to represent relative field strength.

Lines form continuous loops, are denser where the field is stronger and do not cross at a point.

Around a long straight current-carrying wire, field lines are concentric circles whose direction follows the right-hand grip rule.

Magnetic field lines do not begin and end like isolated electric lines; they continue through the magnet.