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

Explanation

1) Place a retort stand on the plank as shown in the figure.
2) Pass a copper wire through hole of the plank and rubber knob of the retort stand in such a way that the wire be arranged in a vertical position and not touch the stand
3) Connect the two ends of the wire to a battery via switch. Allow the current flows through wire.
4) By sprinkling the iron fillings around the wire,we can observe the magnetic field lines are in circular shape.
Conclusion:
Hence it is proved that "Magnetic field lines are closed loops".