1. Magnetism

2. Types of Magnets Permanent Magnets (magnetic once magnetized)
Ferromagnetism
Neodymium Iron Boron (NdFeB or NIB)
Samarium Cobalt (SmCo)
Alnico
Ceramic or Ferrite (Iron, Cobalt, Nickel)
Temporary Magnets – induced from magnetic field
Diamagnetism – found in all matter (very small)
Paramagnetism – stronger than diamagnetism (unpaired e-)
Electromagnets

3. Properties of Magnets north south Magnets have two opposite poles.
Magnets exert forces on each
other.
Like poles repel
Unlike poles attract.
The forces depend on the alignment of the poles.

4. The force between two magnets
The strength of the force between magnets depends on the distance between them.
The magnetic force decreases with distance much faster than does either gravity or the electric force.

5. Magnetic Fields All magnets create a magnetic field
in the space around them, and the
magnetic field creates forces on
other magnets.
The closer the lines are together,
the stronger the field.
Magnetic field lines always point
away from a magnet’s north pole
and toward its south pole.

6. Earth’s Magnetic Field
Moving molten iron and
in nickel Earth’s outer
core causes most of
Earth’s magnetic field.
Field has direction:
lines point away from
N and toward S.
Poles have switched in
the past.

7. Cause of Magnetism
Magnetic fields are produced by moving electric charges.
There are two ways in which electrons create magnetism:
Electrons around the nucleus and their motion makes the entire atom a small magnet.
Electrons themselves act as though they were magnets.
In most materials, electron spin contributes more to magnetism than electron orbital motion.
Electrons are (very) tiny magnets.

8. Cause of Magnetism unpaired electrons can give the atoms an
Electrons with opposite spins (paired e-) cancel each other’s magnetic fields.
Electrons with spins
aligned (unpaired e-)
strengthen each other’s
magnetic fields.
unpaired electrons can
give the atoms an
overall magnetic field.

9. Magnetic Domains
Atoms with similar magnetic orientations line up with neighboring atoms in groups called magnetic domains.
All of the domains of a magnetic substance tend to align themselves in the same direction when placed in a magnetic
field.

10. Electricity and Magnetism
When an electric current passes through a wire a magnetic field is formed.
Right hand rule – wrap in direction of magnetic field,
thumbs points to magnetic north

11. Electromagnet
When an electric current is passed through a coil of wire wrapped around a metal core, a very strong magnetic field is produced. This is called an electromagnet.

12. Electromagnets Changing the strength of an electromagnet
Change the voltage
Change the number of loops