How can you verify with experiment."The magnetic field lines are closed loops"?

Explanation

Aim: To prove that the magnetic field lines are closed lines.
Material required:1)Table 2) wire 3) wooden plunk 4) 24 guage wire 5) 10 compasses 6) 9 volt battery 7) Retort stand

Procedure:
1) Take a wooden plank and make a hole.
2) Place the plank on the table.
3) Now place a retort stand on the plank as shown in the figure.
4) Pass 24 gauge copper wire through hole of the plank and rubber knop of the retort stand in such a way that the wire be arranged in a vertical position and not touch the stand.
5) Connect the two ends of the wire to a 9 volt battery.
6) Place 6 to 10 compasses in a circular path around the hole.
7) pass the current through the wire

Observations: All the needles in all compasses directed in a circular path.
Conclusion: This circular path shows that the magnetic lines are closed loops.