A ferrofluid is just a fluid with suspended
particles of magnetic material (e.g. iron), coated
with a surfactant so that the particles themselves
cannot aggregate together. The fluid itself can be
just ordinary water. Because the suspended
particles can be magnetized in the presence of a
local magnetic field, they will exert forces on
the fluid they are suspended in. Thus, the fluid
will essentially behave as though it were a
magnetic liquid, which of course it isn't - it's a
non-magnetic liquid carrying a suspension of solid
magnetic particles. No, it's not a magnetic
Ferrofluids are fluids that will react to a
magnetic field. They aren't magnetic in the same
way as a bar magnet, though. First, let me
describe how a ferrofluid is made. The magnetic
material in a ferrofluid isn't actually a liquid -
it's a bunch of nano-sized (really, really tiny)
particles suspended in a liquid. The particles
aren't magnetic on their own - they wouldn't stick
to your refrigerator if you put them next to it.
The particles are what we call "paramagnetic".
This means that if we place a magnet next to them,
the magnetic field will cause the particles to
become polarized. Basically what this means is
that the magnetic field turns the particles into
little tiny magnets that will then move around
within the magnetic field, much like iron filings
on a sheet of paper. They won't stick to metal
like a normal magnet, but they will react with
already made magnets.
Other materials will
react in a similar way. Some materials are what we
call ferromagnetic - they can become permanent
magnets, and "emit" their own magnetic field.
These are the normal magnets you would see in
every day life. Other materials are what we call
paramagnetic - they only become magnets once they
are in the presence of a magnetic field. However,
most magnetic materials we encounter in everyday
life are just normal solids, so they don't display
the cool looking shapes of ferrofluids.
materials have properties similar to ferrofluids,
minus the fluid behavior. For example, aluminum is
sometimes considered a paramagnet. This is why a
magnet will stick to your refrigerator (which has
an aluminum casing usually), but a normal piece of
metal will not. It's not a permanent magnet - it
only displays magnetic behavior when in the
presence of a magnet field.
with magnetic shape changing polymers, but I would
suspect that these would basically be like
ferrofluids, assuming they're suspended in some
liquid. If you're talking about just a polymer
sitting on it's own like some sort of plastic or
Styrofoam that will change it's shape in a
magnetic field, then that probably wouldn't be
considered ferro-fluidic, since it's not really a
fluid, but rather an elastic solid. However, it is
still probably displaying paramagnetic behavior,
so it would be very similar to a very fluid.
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