2. What types of magnets are
there?
• There are three main types of magnets:
Permanent magnets
Temporary magnets
Electromagnets
3. Permanent Magnets
• Permanent magnets are those we are most
familiar with, such as the magnets hanging onto
our refrigerator doors. They are permanent in
the sense that once they are magnetized, they
retain a level of magnetism. As we will see,
different types of permanent magnets have
different characteristics or properties concerning
how easily they can be demagnetized, how
strong they can be, how their strength varies
with temperature, and so on.
4. Temporary Magnets
• Temporary magnets are those which act
like a permanent magnet when they are
within a strong magnetic field, but lose
their magnetism when the magnetic field
disappears. Examples would be
paperclips and nails and other soft iron
items.
5. Electromagnets
• An electromagnet is a tightly wound helical
coil of wire, usually with an iron core,
which acts like a permanent magnet when
current is flowing in the wire. The strength
and polarity of the magnetic field created
by the electromagnet are adjustable by
changing the magnitude of the current
flowing through the wire and by changing
the direction of the current flow.
6. Materials used for permanent
magnets
• There are four classes of permanent
magnets:
Neodymium Iron Boron (NdFeB or NIB)
Samarium Cobalt (SmCo)
Alnico
Ceramic or Ferrite
7. Rare Earth Magnets
• Both the Neodymium Iron Boron and the
Samarium Cobalt magnets are generally known
as rare earth magnets since their compounds
come from the rare earth or Lanthanide series of
the periodic table of the elements. They were
developed in the 1970's and 1980's. These are
the strongest of the permanent magnets, and
are difficult to demagnetize. However, the
maximum operating temperature for NdFeB is
the lowest.
8. Alnico Magnets
• Alnico is made of a compound of aluminum,
nickel and cobalt. Alnico magnets were first
developed in the 1940's. This magnet is least
affected by temperature, but is easily
demagnetized. This is the reason why bar
magnets and horseshoe magnets made of
alnico will easily become demagnetized by other
magnets, by dropping it, and by not storing it
with a keeper. Its maximum operating
temperature, though, is the highest.
9. Ceramic Magnets
• Ceramic or Ferrite magnets are the most
popular types of magnets available
today. The flexible magnets we use are a
type of ceramic magnet, with the magnetic
powders fixed in a flexible binder. These
were first developed in the 1960's. This is
a fairly strong magnet, not as easy to
demagnetize as alnico, but its magnetic
strength will vary the most as its
temperature changes
10. Shapes
• Permanent magnets can be made in most
any shape imaginable. They can be made
into round bars, rectangular bars,
horseshoes, rings or donuts, disks,
rectangles, multi-fingered rings, and other
custom shapes. Some are cast into a
mould and require grinding to achieve final
dimensions. Others start as a powder
which is pressed into a mould or pressure
bonded or sintered.
