Sumit Bhowmick

If there is a direct conductor with current, then the presence of a magnetic field around this conductor can be detected using iron filings. Iron filings are yours spikes.

An iron filing will concentrate the magnetic field in itself and if it has a long dimension tend to line up along the field to minimise the potential energy of the field. The field will then be strongest at the two ends and other particles will be attracted here, so the particles line up in the direction of field lines. I think this works even for round particles, especially if two are touching to begin with - they will move to line up along the field direction. The field will be strongroom near these lines so other particles will clump to them.

The reason Ferrofluid forms cone shaped spikes along any pole of a magnet is that the raised apexes are the alternating centripetal and centrifugal points of preponderance which raise themselves not as lines but as cones. Nothing in nature moves in lines, rather in spirals or curve-linear way. To raise any single portion of the Ferrofluid is to create inter-atomic magnetic dilation in the Ferrofluid, which approaches in a cone-first vortex, as any plane of centrifugal acceleration is cone-base first, whereas any vortex plane of expulsion from the magnet is apex first.

From the magnetic energy point of view, the peaks and valleys are energetically favorable. In the corrugated configuration, the magnetic field is concentrated in the peaks; since the fluid is more easily magnetized than the air, this lowers the magnetic energy. In consequence the spikes of fluid ride the field lines out into space until there is a balance of the forces involved.