Download Magnetism

Lesson 1: Intro to Magnetism
What the what is a magnet?
(don’t write)
• Around 600 BCE (a
really long time ago),
the Greeks discovered
an ore that could attract
small iron objects.
• They found this in a
region called Magnesia
(present day Turkey).
Magnets: The Basics
• We now know that magnetite
is a mineral composed of iron
and oxygen (Fe3 O4)
• A magnet is an object that can
attract other objects
containing iron, cobalt or
nickel.
• A ferromagnetic substance is
a substance with the ability to
become magnetic.
To magnet or not to magnet
• Some substances will sometimes act like
magnets and some never will.
WHY?
The reason: Domains!
• If you examine a sample of iron under a
special microscope you will see that it is
divided into sections. These sections are called
domains.
• Only certain substances can organize into
domains.
Neodymium (super magnets)
Image from a Kerr microscope
Becoming Magnetic
I’m
SO
attractive
now!
• The many domains of a magnetic material are not always
aligned.
• When this is the case the substance is not magnetic.
• When the domains align the substance is said to be
magnetized.
•Some magnets will stay aligned forever (permanent
magnets).
Magnetic Poles
• All magnets have a
north and south pole.
Fun Fact #1:
• When two opposite
Younear
can’t break a
poles are brought
each other they magnet
will
into its
attract.
separate North and
• When two same poles
South poles!
are brought together
they will repel.
Earth’s Magnetic Field
Fun
FunFact
Fact#2:
#3:
Earth’s
Earth’s
magnetic
internal
and
geographic
magnet is
poles
slowly
are
oppositely
flipping.
named!
• Earth is a huge magnet, with a magnetic South Pole
and North Pole.
• The magnetosphere (fields created by this giant
magnet) stretch between 200 km and 5000 km beyond
Earth’s surface.
Survival 101: The compass
Thanks for the
fun fact!
Learning about
magnets is
awesome.
• A compass contains a
small magnet, sensitive
to Earth’s magnetic
field.
• While hiking through
the forest your compass
points towards the
North.
• It is actually pointing
towards the magnetic
South of the earth.
The Magnetic Field
• The magnetic field is the space around the
magnet where the magnetic force of a magnet
can act on another magnet.
• Field lines around magnets follow certain rules,
and can be predicted.
• We will use iron fillings to show this effect.
Field Lines: Bar Magnets
Field Lines: Two bar magnets
Field Lines: Horseshoe magnet
Iron Fillings – Bar magnet
Iron Fillings – Repel
Iron Fillings - Attract
Iron Fillings - Horseshoe