Transcript Magnets and Magnetism

Wednesday, January 2nd
Entry Task
What do you know about
magnets and magnetic
forces? Write as many
things as you can think of
Schedule:
• Magnetism Pre-Test
• Bill Nye-Magnetism
Objective: I can understand
basic information about
magnets and magnetism
Homework:
• Read/RSG 21.1
Thursday and Friday
January 3-4
• Mrs. Guttormsen was out and there was a
sub
• There were no entry tasks or objectives for
these days.
• Thursday, Chapter 21 vocabulary was
assigned—Choose a strategy and do for
all words in Chapter 21.
Entry Task
Monday, January 7th
Schedule:
• Magnetism Notes
• Magnetic activity
Decide if the following
statements are true. If they
Objective: I can understand
are write them out as is, if
that magnetism is a force
they are not write out a true
that acts at a distance
statement.
Homework:
• RSG 21.2
1. A force is a push or a pull
2. All forces act at a distance
3. Atoms contain charged
particles
Please have on your desk
• 21.1 RSG
• Chapter 21 Vocabulary
Magnets and Magnetism
• Did you know? More than 2000 years ago, the
Greeks discovered a mineral that attracted
objects containing iron. Because this mineral
was found in a part of Turkey called Magnesia,
the Greeks called it Magnetite. Today any
material that attracts iron is called a magnet.
Magnets and Magnetism
• The magnetic effects of a magnet are
NOT evenly distributed through the
magnet.
• The parts of a magnet where the
magnetic effects are strongest are
called the poles.
Magnets and Magnetism
• If you attach a magnet to a string so that
the magnet is free to rotate, you will see
that one end of the magnet always ends
up pointing north and the other end will
point to the south.
• Magnetic poles always occur in pairs,
you will never find a magnet with only
a north pole or only a south pole.
Magnets and Magnetism
• The force of attraction
or repulsion between
the poles of magnets is
called the magnetic
force.
• The magnetic force
depends on how the
poles of the magnets line
up.
Magnets and Magnetism
• A magnetic field
exists in the region
around a magnet in
which magnetic
forces can act.
Magnets and Magnetism
• Magnetic field lines are close together
where the magnetic force is strongest, and
farther away
where the
force is weaker.
Magnets and Magnetism
• Some materials are magnetic, and some
are not. What causes the difference?
• Whether a material is magnetic depends
on the atoms in the material.
Magnets and Magnetism
• All matter is composed of atoms that include
protons, electrons and neutrons. Moving
electrons produce magnetic fields that can give
an atom a north and a south pole.
• In most materials, the magnetic fields of
individual atoms cancel each other out.
Magnets and Magnetism
• But in some
materials, the atoms
in a magnetic domain
are arranged so that
the north and south
poles of all the atoms
line up and create a
strong magnetic
field.
Magnets and Magnetism
Types of magnets:
Ferromagnets – magnets made with metals
Electromagnets – produced by an electric current.
Temporary magnets – made from materials that
are easy to magnetize, but they lose their
magnetization easily too.
Permanent magnets – difficult to magnetize, but
retain their magnetic properties better.
Entry Task
Tuesday, January 8th
Schedule:
• Finish 21.1 Notes
Draw a diagram that shows • 21.2 Notes- Electromagnetism
the magnetic field that
Objective: I can understand That
result when like poles of
current can produce magnetism
two magnets are close
to each other and when Homework:
two unlike poles are
• 21.3 Read/RSG
close. Use lines to show
the magnetic fields that Please have on desk:
result from these
• 21.2 RSG
situations.
Magnets and Magnetism
In 1600, English
physician William
Gilbert suggested that
magnets point to the
north because Earth
itself is one GIANT
magnet.
Magnets and Magnetism
• Although you can think of Earth as having
a giant bar magnet in the center, there
really isn’t a magnet there.
• The temperature of Earth’s core is so high
that atoms in it move too violently to
remain in domains.
Magnets and Magnetism
• Earth’s magnetic
field is produced by
the movement of
charges in the
Earth’s core.
Magnets and Magnetism
• One of the most spectacular effects
caused by the Earth’s magnetic field is a
curtain of light called an aurora.
Magnets and Magnetism
• An aurora is formed when charged particles
from the sun interact with atoms in Earth’s
atmosphere. We see the interactions at
Earth’s magnetic field.
Magnetism from Electricity
Did you know?
Most trains you see roll on
wheels on top of a track. But
engineers have developed
trains with no wheels that
FLOAT above the track!
These trains are able to
levitate because of magnetic
forces between the track and
the train cars.
Magnetism from Electricity
• Danish physicist Hans
Christian Oersted
discovered the
relationship between
electricity and
magnetism in 1820.
Magnetism from Electricity
• French scientist Andre-Marie Ampere heard
about Oersted’s findings and did more
research. Together, their work was the first
research conducted on electromagnetism.
• Electromagnetism is the interaction
between electricity and magnetism.
Magnetism from Electricity
• Although the magnetic field created by an
electric current in a wire may deflect a
compass needle, it is not strong enough to
be very useful.
• Two devices, the solenoid and the
electromagnet, strengthen the magnetic
field enough to be useful.
Magnetism from Electricity
• A solenoid is a coil of wire that produces
a magnetic field when carrying an electric
current.
Magnetism from Electricity
• The strength of the
magnetic field increases
as more loops of wire
are added and as the
current in the wire is
increased.
Magnetism from Electricity
• An electromagnet is a
magnet that consists of a
solenoid wrapped around an
iron core. The magnetic field
produced by the solenoid
causes the domains in the
iron to become better
aligned.
Magnetism from Electricity
• An electric motor is a device that
changes electrical energy into kinetic
energy.
• All electric motors have an armature, a
loop or coil of wire that can rotate. The
armature is mounted between the poles of
a magnet.
Magnetism from Electricity
• A simple DC electric
motor. When the coil is
powered, a magnetic field
is generated around the
armature. The left side of
the armature is pushed
away from the left magnet
and drawn toward the
right, causing rotation.
Magnetism from Electricity
• The armature
continues to rotate
Magnetism from Electricity
• When the armature
becomes horizontally
aligned, the commutator
reverses the direction of
current through the coil,
reversing the magnetic field.
The process then repeats.
Wednesday, January 9th
Entry Task
Decide if the following
statements are true. If
they are, write them
down as is. If they are
not, write down a
correct statement.
1. Like charges attract one
another
2. Electric current can
produce a magnetic field
3. Motors contain magnets
Schedule:
• Magnetism can produce
current diagrams
Objective:
•I can understand that
magnetism can produce current
Homework:
• Complete Diagrams
Please have on Desk:
• 21.3 RSG
21.3 Diagrams
• Draw a labeled diagram/picture explaining how
the following work
–
–
–
–
–
Generator
Direct Current
Alternating Current
Step up transformer
Step down transformer
• You may want to use numbered steps of the
process or you may want to write a paragraph
explaining
• Include all parts, definitions, labels,
EVERYTHING
Thursday, January 10th
Entry Task
Answer the following questions
using full sentences, IQIA
1. What happens when you turn
off the current in an
electromagnet?
2. Why is an electromagnet more
useful than a permanent
magnet to separate a mixture
of metals?
3. How could you make a motor
stronger?
Schedule:
• Magnetism from
current lab
• Investigate
electromagnets
Objective: I can
understand that current
can produce magnetism
Homework: Finish Lab
Worksheets
Entry Task
Friday, January
Write down the following
definitions and match them
with a correct term
th
11
Schedule:
• 21.3 Notes
Objective:
•I can understand that
magnetism can produce
current
1. The force exerted by
magnets
2. A device that uses magnetism Homework
to produce current
• Answer questions 1-6
3. A device that uses current to
from page 723 using full
produce magnetism
sentences, IQIA
Electricity from Magnetism
• When you use an electric appliance or
turn on a light in your home, you
probably don’t think about where the
energy comes from.
• How does a magnetic
field produce electric
current?
Electricity from Magnetism
• In 1831 Michael Faraday was able to
generate an electric current from a
magnetic field.
Electricity from Magnetism
• Faraday showed that
the magnetic field
around a wire can be
changed by moving
either the magnet in
and out of a coil of wire
OR by moving a wire
between the poles of a
magnet.
Electricity from Magnetism
• A generator is a device that uses
electromagnetic induction to convert
kinetic energy into electrical energy.
Electricity from Magnetism
• The electric current
produced by the
generator changes
direction each time the
coil makes a half-turn.
Because the electric
current continually
changes direction, the
electric current is an
alternating current.
Electricity from Magnetism
• In hydroelectric plants, water flowing
downhill turns a turbine. The turbine
turns the magnet of a generator,
inducing electric current.
Electricity from Magnetism
• In nuclear power
plants, thermal
energy created
by a nuclear reaction
boils water to
produce steam which
turns a turbine.
Electricity from Magnetism
• Another device that relies
on electromagnetic
induction is a transformer.
• A transformer increases
or decreases the voltage
of an alternating current.
• A simple transformer
consists of two coils of
wire wrapped around an
iron ring.
Electricity from Magnetism
• The electric current
that provides your
home with electrical
energy is usually
transformed 3 times
before it reaches
your home.
Electricity from Magnetism
1. The power plant
produces electric
current with high
voltage. To decrease
the loss of power over
long distance
transmission, step-up
transformers increase
the voltage thousands
of times!
Electricity from Magnetism
2. The electricity travels over transmission
lines with very high voltage to a
distribution station with a step-down
transformer that lowers the voltage.
Electricity from Magnetism
3. The electric current
travels over local
power lines to
another step-down
transformer which
lowers the voltage
again before the
current reaches your
house.