Download Magnetism (High School)

Unit 3: Magnetism
Learning Targets for this Unit:
 I can conduct an investigation to
explain how magnetic fields are
created

I can diagram (explain with words and
pictures) how magnetism is a force of
magnetic domains and magnetic fields.
Properties of Magnets
 All magnets have two areas of strongest force, called
poles.
 Each magnet has one north pole and one south pole.
 Like poles repel, and opposite poles attract.
 The magnetic region where you can “feel the force” is
called a magnetic field.
Try out this interactive magnetic field link: http://phet.colorado.edu/en/simulation/faraday
Magnetic Materials
 What makes some things magnetic,
while other things can’t be
magnetized?
 Randomly arranged domains =
No magnet!
 Spinning electrons cause small
magnetic fields around each atom.
 Magnetic materials have atoms
whose magnetic fields can be lined
up in the same direction.
 Areas where atoms’ magnetic fields
line up are called magnetic domains.
(magnetic domain
)
 Magnetic domains lined up =
Magnet!
Electricity & Magnetism
 Electricity can cause magnetism! You can make a magnet by using
electricity to magnetize the domains in iron. These are called
electromagnets
 Electromagnets are powerful magnets that can be turned on and
off.
You can make an electromagnet stronger by:
(1) putting more turns of wire in the coil
(2) making a larger soft iron core
(3) increasing the current through the wire.
Let’s Try it!!
Using an iron nail, wire, and a nine-volt
battery, we will attempt to create an
electromagnet that may be able to pick up
some paper clips!
Uses for electromagnets
LET’S FIND OUT….
http://science.howstuffworks.com/electro
magnet.htm
Read the article and list at least three
things that have electromagnets in
them.
Let’s turn it around… Magnetism can
create ELECTRICITY
 Magnetism can produce
electric current. This is
called electromagnetic
induction.
 If a magnet is moved back
and forth through a coil of
wire, current can be made to
flow through the wire. This
is the idea behind electric
generators and transformers.
Uses for Electromagnetic Induction
 Devices that use magnetism to
induce currents include
generators, pickup coils in
electric guitars, transformers of
every size, certain microphones,
airport security gates, and
damping mechanisms on
sensitive chemical balances.
Using Electromagnets to Make Sound
 How does musical information stored
on a CD become sound you can hear?
 The sound is produced by a
loudspeaker that contains an
electromagnet connected to a flexible
speaker cone that is usually made
from paper, plastic, or metal.
 The electromagnet changes electrical
energy to mechanical energy that
vibrates the speaker cone to produce
sound
Earth’s Magnetosphere
Like many Planets in our Solar System
the Earth has a Magnetic Field
The Earth behaves as if there was a magnet in its interior. The
Earth’s magnetic field comes from the currents in the molten
iron core. These currents create a complex magnetic field that
ends up acting like a bar magnet
S
N
The North Pole of the Earth has a “south” polarity.
As a result a compass will always point towards the North.
A compass is a Magnetized piece of metal that can spin.
S
N
Try It
Look at a compass…can you find which
way is north?
Go stand by the northern-most wall in the
classroom
What happens when you get a magnet
near a compass?
A Magnetic Field also protects us from the Solar Wind.
The Sun produces a stream of charged particles that spread
throughout the solar system.
These particles are deflected by the Earth’s Magnetic Field
Read Article
“Earth’s Magnetic Field Provides Vital Protection”
Published March 8th, 2012
The Earth’s Magnetic Field is created in the
same way you make an electromagnet
The Earth is made of four layers
1. The Crust:
A Thin Rock Material
2. The Mantle:
A Dense and Mostly Solid
Rock Material
3. The Outer Core:
Liquid Iron and Nickel
4. The Inner Core:
Solid Iron and Nickel
The Iron Core of the Earth is an Electromagnet
The core is surrounded by
liquid Iron and Nickel
As electrons flow around the
core the magnetic field is
produced
The Earth’s rotation makes
the electrons flow at very
high speeds
Other Planets in our Solar System have
Magnetic Fields
Planet
Magnetic Field
Mercury
100 times weaker than Earth
Venus
25,000 times weaker than Earth
Earth
30,000 – 60,000 nT
Mars
5000 times weaker than Earth
Jupiter
20,000 times greater than Earth
Saturn
540 times greater than Earth
Uranus
40 times greater than Earth
Neptune
¼ that of Earth
Pluto
None that we know of
Let’s see some visuals…
Take a break to watch
“Magnetic Storm: Earth's Invisible Shield “
Magnetism &
the Sun:
Almost everything in the universe is made up of atoms
which are made of protons, electrons, and neutrons
Hydrogen has one electron and one proton
The Sun is made mostly of hydrogen
In the right pressure environment, as solids are
heated, they turn to liquids. Liquids, if heated enough,
will turn to gas
Magnetism and the Sun
The Sun is SO hot because gravity pulls its mass
together so strongly that near the core of the sun
atoms fuse together. This fusion converts Hydrogen to
Helium and energy. This energy gets absorbed and
turned into heat
The Sun is SO hot that electrons cannot stay attached
to the nucleus of the atoms. This means that the Sun
is mostly a hot, electrically charged gas known as
plasma
The Sun’s magnetic field comes from currents in and
around the Sun that are caused by the moving
“plasma”
Read Article
“The Sun”
Published July 16, 2010
Planets and Magnetic Fields
How do we measure the magnetic fields that exist
between planets?
If we wanted to learn more about the magnetic fields
that are ejected by the Sun we could send a satellite
into space with some way to measure the magnetic
field…such as a compass or magnetometer
We have to go into space to do this because the
magnetic field of the Sun at Earth’s distance is 10,000
times less strong than the Earth’s own magnetic field
so it interferes with true measurement of the Sun’s
magnetic field
A planet’s magnetic field is measured using an
instrument called a Magnetometer
Many spacecraft carry Magnetometers to
measure the Magnetic Field.
Mars Global Surveyor
Advanced Composition Explorer
Check out this clip about magnetometers
http://youtu.be/E8tEdlvnXJc
Galileo
What is electromagnetic energy?
Electromagnetic energy is a term used to describe all the
different kinds of energies released into space by stars
such as the Sun.
These kinds of energies include:
Radio Waves
TV waves
Radar waves
Heat (infrared radiation)
Light
X-rays
Gamma Rays
Ultraviolet Light (This is what causes Sunburns)
Microwaves, like in a microwave oven
What is Electromagnetic Energy?
(continued)
All these waves do different things but they have some
things in common.
They all travel in a way that is like the waves at a beach
They are made of tiny particles.
We can measure the different kind by wavelength. That is
one way we can tell the kinds of radiation apart from each
other.
Although all kinds of electromagnetic radiation are released
from the Sun, our atmosphere stops some kinds from
getting to us. For example, the ozone layer stops a lot of
harmful ultraviolet radiation from getting to us, and that's
why people are so concerned about the hole in it.