Transcript Magnets - HuntNorthStar

Magnets
What is a magnet?
• A magnet is an object that has the
property of attracting certain
materials, mainly iron and steel.
Property?
• Properties are the
characteristics of
an object.
What are the properties of
water?
What does it feel like?
What does it look like?
What can it do?
• A characteristic is
the way
something is.
• For example a
person’s
characteristics
could be; She is
funny and tall.
•
Magnets have many
All metals are made
properties….
up of atoms that are
usually jumbled
around.
• A metal becomes a
magnet when the
atoms line themselves
up straight.
• Iron, Nickel and
Cobalt (or some
mixture that has one
of the metals) are the
only metals that can
be turned into a
magnet.
• Steel has iron in it.
Which metal is a magnet?
What is
another
word for
property?
Characteristic
poles
• Pole- the area
on a magnet
where the
magnetic force
is strongest.
• All magnets have
a north and south
pole.
north
south
North and South
• A property of a
magnet is that every
magnet has a North
Pole and a South Pole.
• Opposite poles attract
(come together) each
other.
• Like poles repel (move
away from) each
other.
• Attract - the act of
trying to come
together.
• The pushing apart of
magnets that occurs when
two north ends (or two
south ends) of two magnets
are brought close to each
other.
repel
attract
• The act of trying to come together.
• Opposite poles are attracted to each
other.
• Example: the north pole of one magnet
is attracted to the south pole of
another magnet.
More properties of
magnets
Magnets have a magnetic field.
• A magnetic field
is the area around
a magnet where
you can detect
the force of the
magnet.
www.school-for-champions.com/science/images/magnetic_detection-iron_filings.jpg
Magnetic Field
• The magnetic
field is always
strongest near
the poles!
• If you cut a magnet
in half you will have
two new magnets.
They will both have
a North and a South
pole.
http://www.how-things-work-science-projects.com/second-gradescience-projects.html
Strong magnetic field
• The Earth has a
very strong
magnetic field.
Weak magnetic field
• A bar magnet has
a weak magnetic
field.
Strong magnetic
field.
Weak magnetic field.
Magnetic Force
• The power of a
magnet to push
or pull other
magnetic
material.
• The strength of
the magnetic field
is the magnetic
force.
Different types of
magnets……
Natural Magnets
• A natural magnet
is an object
fournd in nature
which has a
magnetic field
around it. An
example of a
natural magnet is
the rock
Magnetite.
Natural Magnet
Natural magnet
Examples of Natural
Magnets
magnetite
• The most popular legend
accounting for the discovery of
magnets is that of an elderly
Cretan shepherd named
Magnes. Legend has it that
Magnes was herding his sheep
in an area of Northern Greece
called Magnesia, about 4,000
years ago. Suddenly both, the
nails in his shoes and the
metal tip of his staff became
firmly stuck to the large, black
rock on which he was
standing. To find the source of
attraction he dug up the Earth
to find lodestones (load = lead
or attract). Lodestones contain
magnetite, a natural magnetic
material Fe3O4. This type of
rock was subsequently named
magnetite, after either
Magnesia or Magnes himself.
• Lodestones were used to tell
direction.
Magnetite
http://www.howmagnetswork.com/history.html
Permanent magnets
Permanent Magnets
• A permanent magnet is a
man-made object with a
magnetic field around it.
It has parts that are
usually labeled as North
and South. It will keep
its magnetism for a long
period of time.
• A permanent magnet can
be demagnetized by
heat, hammering and by
other magnets.
http://www.coolmagnetman.com/images/alnico2.jpg
Examples of permanent
magnets
horseshoe
bar
donut
Temporary magnet
Temporary Magnets
• A Temporary
Magnet is an
object which has
a magnetic field
around it for a
short period of
time. An example
of a temporary
magnet is an
electromagnet.
Examples of temporary
magnets
• Electromagnet
Electromagnet
• A temporary
magnet made by
passing an electric
current through a
wire coiled around
an iron bar.
H
• The strength of
the electromagnet
depends on the
strength of the
power source and
the number of
coils wrapped
around the bar.
How can we make this
electromagnet stronger?
Electromagnet
• A junkyard is one place to
see an electromagnet in
action. A crane holding a
huge electromagnet can be
used to pick up scrap metal
when current flows through
it. When the crane operator
wants to drop the scrap, he
or she will simply shut off the
current to the electromagnet.
http://www.bbc.co.uk/schools/ks3bitesize/science/physics/magnetism_5.sht
ml
Earth’s Magnetic Field
• THE EARTH DOES
NOT CONTAIN A
GIANT BAR MAGNET,
BUT IT BEHAVES AS
IF IT DOES. THE
EARTH HAS A
MAGNETIC NORTH
POLE AND A
MAGNETIC SOUTH
POLE.
http://www.bbc.co.uk/schools/ks3bitesize/science/physics/magnetism_5.sh
tml
We use Earth’s magnetic
field to figure out where
we are.
• A compass is an object
with a small magnetic
section that detects the
north pole of Earth and
points to it.
• the north pole of a bar
magnet is actually called
the 'north-seeking pole',
and it points to the
Earth's magnetic north
pole;
• the south pole of a bar
magnet is actually called
the 'south-seeking pole',
and it points to the
Earth's magnetic south
pole.
Compass
Where am I?
• The south pole of a magnet is attracted to the
Magnetic North Pole of the Earth. The south
pole of a bar magnet is labeled "N." This can
be confusing.
• A famous aviator nicknamed "Wrong Way
Corrigan" flew from New York to Ireland when
he was supposed to be going to Kansas. He
claimed he followed the wrong end of his
compass.