Topic explanation

Standard explanation

A ferrofluid is a stable colloidal suspension of magnetic nanoparticles in a carrier liquid.

Key points

• A ferrofluid is a stable colloidal suspension of magnetic nanoparticles in a carrier liquid.
• The particles are commonly iron oxide and are about 10 nm in diameter.
• A surfactant coats the particles and prevents them from clumping together.
• Without an external field, thermal motion leaves the particle moments randomly oriented.
• In a magnetic field, the particles align and the fluid is attracted toward stronger field regions.
• Strong fields can produce surface spikes through a balance of magnetic force, gravity and surface tension.
• Ferrofluids are used in seals, loudspeakers, heat transfer, sensors and specialised medical research.

Labelled diagram