Transcript Magnetism - Physical Science

Magnetism
• property of matter in which there is a
force of attraction or repulsion b/w like
or unlike poles
What do we know about magnets?
• 2 Magnetically opposite poles:
– North Pole and South Pole
• Like poles repel and Opposite poles
attract
– “We’ll get back to this later”
What types of things do magnets
attract?
• “Do magnets attract all metals?”
1st
– Magnets only attract objects made of iron, cobalt,
or nickel!!
• These metals are called the “Iron Triad”
– See Periodic Table
• You can also only make a magnet out of these
3 metals.
• Those “rubber” magnets have iron, cobalt or nickel in
them.
Magnetic Domains
• The molecules of most
substances have no
orientation to them.
• In a magnet, the
molecules align
themselves in a very
specific pattern.
I wonder
why?
Magnetic Field
• Surrounding all magnets is a magnetic
field.
• Magnetic Field is the area surrounding a
magnet where the magnetic force acts.
Magnetic Field Lines
Magnetic Field Lines
always move out of
the North pole and
into the South pole!!
What makes the
North Pole the
North Pole and
the South Pole the
South Pole?
It is not the N
and S stamped
on them!!!!
The North Pole is
the pole that the
magnetic field
lines move out
of.
The South Pole is
the pole that the
magnetic field
lines move into.
Magnetic Field Lines
• Magnetic Field lines always move out of
the North end and into the South end!!
Magnetic Field Lines of
Interacting Magnets
Lines of Repulsion
Lines of Attraction
Solving for Unknown Poles
Are the field lines attracting or repelling?
attracts
North ____________
what?
Solving for Unknown Poles
Are the field lines attracting or repelling?
North __attracts______ what?
Solving for Unknown Poles
Are the field lines attracting or repelling?
repels
North ____________
what?
Solving for Unknown Poles
Are the field lines attracting or repelling?
North __repels____ what?
Determine the unknown pole
A. North
B. South
Determine the unknown pole
A. North
B. South
Where are Magnets the strongest?
I wise man told me
many years ago that
“Magnets are
strongest at the
poles”. That is
where the magnetic
field lines are the
most concentrated.
Which of the following metals would
not make a very good magnet?
A.
B.
C.
D.
Iron
Cobalt
Aluminum
Nickel
What happens if
you break a bar
magnet in half?
You get 2 bar
magnets both with
a North and a
South pole!!
Mr. Garay
Breaking a Bar Magnet
Where is this magnet the strongest?
A. 1 only
B. 2 only
C. 3 only
D. 1 and 3
Where is this magnet the strongest?
A. 1 only
B. 2 only
C. 3 only
D. 1 and 2
If you broke a bar magnet in half and then
broke both halves in half again, how many
bar magnets would you have?
A. Not possible
B. 2
C. 4
D. 8
Note-taking Skills Worksheet
• A. Magnetism—the properties and
interactions of magnets.
– 1.Interaction b/w 2 magnets, called
magnetic force, increases as magnets move
closer together.
– 2. A magnetic field, which exerts the
magnetic force, surrounds a magnet, and is
closest to the magnet.
Note-taking(cont.)
• B. Magnetic Poles—the region of a magnet
where the magnetic force exerted by the
magnet is strongest.
– 1. All magnets have a north and a south pole.
– 2. Like poles repel. Unlike poles attract.
– 3. Earth has magnetic poles.
• A) A compass needle is a small bar magnet that can
freely rotate.
• B) A compass needle always points north.
Note-taking(cont.)
• C. Magnetic materials—iron, cobalt, and nickel
– 1. The magnetic field created by each atom exerts
a force on nearby atoms.
– 2. Magnetic domains—groups of atoms with
aligned magnetic poles.
• A) In a magnet, the like poles of all the domains point in
the same direction.
• B) Permanent magnets are made by placing a magnetic
material in a strong magnetic field, forcing a large
number of magnetic domains to line up.