2. Types of magnets:
◦ Permanent magnets retain a magnetic field indefinitely
Ferromagnetic substances are naturally magnetic
Magnetite/hematite: naturally occurring iron oxide
Some transition metals: iron, copper, or nickel.
Some rare earth metals: neodymium, gadolinium, samarium
◦ Temporary magnets lose their magnetic field strength over time, or
can be turned off and on.
Magnetized paper clips or needles are paramagnetic (can be
magnetized for a short time)
Electromagnets become magnetic under the influence of an electric
current
No longer magnetic when electricity flow is stopped
Can easily be turned off and on
…any substance that contains a
magnetic field.
3. The directional spin of electrons create tiny magnetic regions
called domains
◦ In some atoms, these domains cancel out
◦ In magnets, domains are all lined up in same
direction
Whenever all electrons spin in the same direction, a
magnetic field is produced
4. A material such as iron that can be magnetized
because it contains magnetic domains.
5. A substance that reacts to magnetic fields, but
does not remain so after the field is removed.
Liquid Oxygen can remain suspended between
two magnets.
6. Magnetic force =the push or pull a magnet exerts
◦ on another magnet
◦ on iron or a similar metal
◦ or on moving charges (electricity)
7. Magnetic field lines – single magnet
Iron filings lining up along the magnetic field Like poles of two magnets repel each other
Magnetic field lines show attraction
between opposite poles of two magnets
8. Hold a magnetic field indefinitely.
Iron, Cobalt, and Nickel are the only substances
that are naturally magnetic.
◦ Co and Ni are somewhat rare, so the vast majority of
magnets are made of iron.
Euro pennies have steel
9. Electromagnets can easily be
made at home with a copper wire, a
nail, and a battery.
Wrap the wire around the nail and
hook it to the positive and negative
ends of the battery.
When electrons flow through the
wire, they induce a magnetic field
around the nail which can then
attract iron objects.
10. Strength controlled by:
◦ Neatness of coiling
◦ Number of loops
◦ Wire gauge (thickness)
◦ Battery strength (more
voltage = stronger)
◦ Magnetic permeability of the
core material
◦ Temperature (colder =
stronger)
11. An electromagnet starts with a power source and a wire.
◦ Batteries/Electricity produce electrons.
◦ Flowing electrons produce an electric field, which induces a magnetic field.
Electromagnetic devices are used to change electrical energy into
mechanical energy.
◦ Examples of electromagnetic devices: electric motors, galvanometers, loud speakers,
doorbells, automatic car door locks.
12. A magnetic field in a current
carrying wire can be increased by
wrapping the wire into a coil. This
coil of wire is called a solenoid
When a iron core (like a metal
rod) is placed in a solenoid, an
electromagnet is formed
This is the basis of many
electric motors.
13. The magnetic field is a dipole field.
◦ That means that every magnet MUST
have two poles (a north and a south
pole).
Electrical charges are called
monopoles, since they CAN exist
without the opposite charge.
14. This magnetic field forms circles
around a straight wire carrying
the current.
Point your thumb in the direction
of the current
If you curl your fingers around
the wire, the way your fingers
curve is in the direction of the
magnetic field.
15. If electricity creates a magnetic field, the opposite is
also true!
When a magnetic field rotates within a coil of wire, it
generates an electric current.
A hand-cranked dynamo charges a battery for an emergency radio…
Or you can have a hamster do it
16. Use water or wind to turn magnets to
generate electricity
17. An electric current
flowing around a rod will
make a magnet.
It is called an
electromagnet
A moving magnetic field
within a looped wire will
make electricity.
It is called a generator
18. The Earth acts as a giant
electromagnet.
The swirling liquid iron-
nickel outer core moves
around a solid iron-nickel
inner core.
Electrons moving within
the liquid create an electric
current.
The electric current
creates a magnetic field
that extends around the
planet.
19. The moving current around the iron core acts like an
electric current flowing around a core, creating a
strong electromagnetic field.
20. The Earth’s magnetic field protects us from harmful solar
particles by deflecting or absorbing them.
The aurora borealis is located at the north pole, because
that is where the energized solar particles come shooting
down into the atmosphere.
