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Magnetism!!
OA3.1 Understand electricity and
magnetism
OA3.1.2 Explain how magnetic poles
behave
Warm up!
1. What do your remember that we
learned in class about magnets?
2. What type of objects do magnets
attract?
A little background
info…
Magnets have been known for centuries.
The Chinese and Greeks knew about the
“magical” properties of magnets. The ancient
Greeks used a stone substance called
“magnetite.” They discovered that the stone
always pointed in the same direction. Later,
stones of magnetite called “lodestones” were
used in navigation.
William Gilbert, an English
physician, first proposed in
1600 that the earth itself is a
magnet, and he predicted that
the Earth would be found to
have magnetic poles.
What is a magnet?
A magnet is a solid substance that attracts iron
or steel.
What is magnetism?
Magnetism is the state of being magnetized
What are poles of a magnet?
Each end of a magnet is called a pole.
This is where the magnetic force is the strongest.
If a magnet was held by a string, one pole will point
north and the other will point south.
Hence, a magnet has 1 north and 1 south pole.
What is a magnetic field?
The region where the magnetic forces act is called the
magnetic field.
Magnetic field
Magnetic field pictures
How do poles act like electrical charges?
S
N
A typical bar magnet
Opposites
Like
repelsattract!!
like!!
Why? Because of the magnetic field
around the magnets!
Like
Opposites
repelsattract!
like…
The earth is a giant magnet!
The nickel iron core of the earth gives the earth a
magnetic field much like a bar magnet.
What is a compass?
A compass helps you see
what direction you are
facing.
The needle is a magnet that
points toward the North
and South poles.
Electricity and Magnetism – how
are they related?
When an electric current passes through a wire a
magnetic field is formed.
What is an 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.
Closure questions
1. The two ends of a bar magnet that point northsouth are called the ______________.
2. The region around a magnet where the
magnetic force acts is its _________________ .
3. Would the magnets below be attracted to one
another or repel one another?