Magnetic field of a bar magnet. Iron filings on a sheet of paper after the removal of a bar magnet. The filings mark the lines of the bar magnet's magnetic field. The lines radiate outwards from each end (pole) of the bar magnet, forming large loops that circle round to the other pole. Where the lines converge (here, inside the magnet) the magnetic field is strongest. Where they diverge, the field is weakest.