Transcript What is a magnet?

Magnets
Magnet
Activity #1
What will move a magnet?
Test the items listed below to see if
they can make the magnet move. The
next slide will reveal the answers.
Yes
No
Item
Pencil
Paper Clip
Penny
Marble
Scissors
Nuts & Bolts
Nickel
Button
What will make a magnet move?
Item
Pencil
Paper Clip
Penny
Marble
Scissors
Nuts & Bolts
Nickel
Button
Yes
No
Paper clips
attract...
because they are
made of iron.
Scissors
attract.
because they are
made of iron.
Nuts and
bolts attract.
because they are
made of iron.
Refrigerator magnets
Shower curtain weights
TV deflection coil
Telephone receivers
Credit card magnetic strip
Headphones
Power supply transformers
Magnets
in my
house
Phone ringers
Computer monitor, hard drive, speakers
Microwave tubes
Seal around refrigerator door
What is a magnet?
•
Caused by
electron spin
•
An object in which all domains are aligned in the same
direction
•
Composed of ferromagnetic material (iron, nickel,
cobalt, gadoliniuim).
What are magnetic domains?
Magnetic substances like iron, cobalt, and nickel are
composed of small areas where the groups of atoms are
aligned like the poles of a magnet. These regions are
called domains. All of the domains of a magnetic
substance tend to align themselves in the same direction
when placed in a magnetic field. These domains are
typically composed of billions of atoms.
Magnetized Objects
Unmagnetized
Magnetized
For every North, there is a South
If you take a bar magnet and break it into two pieces, each
piece will again have a North pole and a South pole.
S
N
S
N S
N
No Monopoles Allowed - It has not been shown to be possible
to end up with a single North pole or a single South pole, which
is a monopole
S
N
Temporary
Magnet
a material that is
easily magnetized and
loses its magnetism
quickly
VS
Permanent
Magnet
materials that are
hard to magnetize and
will also stay
magnetized for a long
time
Magnetic Field Lines
Magnetic field lines can be drawn in the direction a
north pole of a compass needle would point if
placed at that point. The number of lines per area
show the strength of the field at that point.
Uses of magnets
• Magnets were first put to use in navigation
because they always point north and south.
• Magnets are used to hold, separate, control,
convey and elevate products and to convert
electrical energy into mechanical energy or
convert mechanical energy into electrical
energy.
Ways to demagnetize a magnet
1.) Strike the
magnet with force
2.) Heat it
The earth is
like a giant
magnet!
The nickel iron core of
the earth gives the
earth a magnetic field
much like a bar
magnet.
We use the Earth’s magnetic field to find direction.
The needle of a compass always points toward the
magnetic south pole.
We call this direction “North” (remember, opposites attract)
Activities #2 - #4
Supplement – What is in your breakfast
Electricity and Magnetism – how
are they related?
1.) When an electric current passes through a
wire a magnetic field is formed.
2.) when a wire is moved across a magnetic field,
an electric current is induced in the wire
Demos & Activities
Magnet from electricity
• ELECTROMAGNET
Electricity from magnets
• ELECTRICAL INDUCTION
See Activity #4
In general, who has a better sense
of direction?
1. Males
2. Females
Fun Fact
Humans have a small number of very tiny iron
filings in the bone and cartilage of the nose,
right in the center near the eyes. There is
evidence that people can use these filings to
orient themselves toward magnetic north even
when blindfolded. MALES tend to have more
of these filings, which explains why males
tend to be better at geographic orientation
(and why females tend to rely more on street
names and other identifiable features).
Fun with Magnets
http://www.youtube.com/watch?v=wOv0AkphLhE