In this lecture you will learn about:
the force called magnetism
where magnetism comes from
the Earth as a big magnet
magnetism and electricity
"Electromagnetism is the physics of
the electromagnetic field, a field which exerts a force on particles
with the property of electric charge and which is reciprocally affected
by the presence and motion of such particles.
A changing magnetic field produces an electric
field (this is the phenomenon of electromagnetic induction, the basis of
operation for electrical generators, induction motors, and transformers).
Similarly, a changing electric field generates a magnetic field.
The magnetic field is produced by the motion
of electric charges, i.e., electric current. The magnetic field causes
the magnetic force associated with magnets." wikipedia
|Magnetism is a force over distance,
|It has "fields or lines that emanate evenly
in all directions
for a java showing iron filings aligning in an
Electrical magnetic filed
|When a + charge and a - charge are within
the fields are distorted in the direction
of the attracting forces
When two like charges, +/+ or -/- are within
the fields are also distorted, but away
from each other
for a java showing this
WHERE DOES MAGNETISM COME FROM?
|"Spin is an intrinsic angular momentum
of particles such as electrons, and has an associated magnetic
field, much like that of a bar magnet." 1
"In most materials, atoms are arranged
in such a way that the magnetic orientation of one electron cancels out
the orientation of another. The ferromagnetic iron and its binary iron
- chromium alloys are different. Their atomic arrangement is such that
groups of atoms band together into small areas called Weiss domains, in
which the magnetic moments of atoms ("elementary magnets") are uniformly
oriented in the same direction, even without an external magnetic field."
|Natural magnets are oxides of iron (colored
Heating destroys the alignment of iron
As lava cools any iron particles align
with the existing magnetic field of Earth
|Electric magnets are strong enough to
pick up cars and can be turned off when they want to drop the car into
a crusher. Also good for separating metals from non-metals.
TIP: When shopping for used car.
Take along a magnet and test the panels of the car for iron because some
cars that have been in an accident have fiberglass fill and the magnet
THE EARTH, THE SUN, MOST OF THE
PLANETS ARE BIG MAGNETS
|What causes earths magnetic fields?
It has been a classic case of scientific
method where the hypothesis and theories have come, been challenged and
gone down in flames.
|1. The liquid metal part of Earth's
core has been suspected as the source of Earth's magnetic fields
||PFFFT. But molten stuff doesnt have
|2. The solid iron core is the source
of the fields
||PFFFT. The sun and Jupiter dont
have an iron core, they do have magnetic fields
|3. Rotation of earth affects liquid
outer core and this produces magnetic field
||AHA!: slow rotating planets like Venus
and Mercury have weaker magnetic fields than Earth and Jupiter and Saturn,
which rotate faster and have stronger magnetic fields.
EARTH'S MAGNET AND THE VAN ALLEN
|"The Van Allen radiation belt is a torus
of energetic charged particles (plasma) around Earth, which is held in
place by Earth's magnetic field. This field is not uniformly distributed
around the Earth. On the sunward side, it is compressed because of the
solar wind, while on the other side it is elongated to around three earth
It is split into two distinct belts, with
energetic electrons forming the outer belt and a combination of protons
and electrons creating the inner belt. In addition, the belts contain lesser
amounts of other nuclei, such as alpha particles. The Van Allen belts are
closely related to the polar aurora where particles strike the upper atmosphere
Prior to the Space Age, the possibility
of trapped charged particles had been investigated by Kristian Birkeland,
Carl Størmer, and Nicholas Christofilos. The existence of the
belt was confirmed by the Explorer 1 and Explorer 3 missions in early 1958,
under Dr James Van Allen at the University of Iowa. The trapped radiation
was first mapped out by Sputnik 3, Explorer 4, Pioneer 3 and Luna 1." wiki
|FLARES are huge spurts of hot gas that
erupt from areas of sunspots. When they hit the Van Allen belts, they cause
a distortion of the magnetosphere.
Van Allen belts (the magnetic field) protects
us from SOLAR WIND. solar wind is bare nuclei and electrons, ionic particles
that are thrown out by solar activity. MOST solar wind particles are deflected
around and past earth.
MAGNETIC FIELDS/VAN ALLEN BELTS
+ SOLAR FLARES = AURORA BOREALIS AKA NORTHERN LIGHTS
|FLARES are huge spurts of particles that
erupt from areas of the sun called sunspots. When they hit the Van
Allen belts, the very energetic charged particles are captured in the Van
Allen belts/magnetic fields and travel down magnetic lines into the atmosphere
where they smash into air molecules. Radiation in the visible is
given off. What we see is the AURORA BOREALIS or Northern lights.
"The collisions in the atmosphere electrically
excite electrons to take quantum leaps (a mechanism in which the electron's
kinetic energy is converted to visible light); and molecules in the upper
atmosphere. The excitation energy can be lost by light emission or collisions.
Most auroras are green and red emissions from atomic oxygen. Molecular
nitrogen and nitrogen ions produce some low level red (pink) and very high
blue/violet auroras. The light blue and green colors are produced by ionic
nitrogen and the neutral helium gives off the purple colour whereas neon
is responsible for the rare orange flares with the rippled edges.". wiki
For Aurora alerts click here
WHAT DOES MAGNETISM HAVE TO DO
|We would still be burning gas for light
and riding horses if the generator had not been invented. The electrical
generator depends upon another physical property: MAGNETISM, WHICH IS TOTALLY
DEPENDENT UPON MOVING ELECTRONS.
|This is the crux, the nub, the whole enchilada
here. Get a cup of coffee, this is IT.
|The flow of the electrical charge or field
through a wire will induce (cause) a magnetic field. Click
HERE to see this
A rapidly rotating magnetic field will
induce (cause) an electric current in a wire! Click HERE
to see this
SO, if you use a water (hydroelectric)
or steam (from burning coal or nuclear) to turn a wheel, it can rotate
a magnet inside of a coil of wire and this will induce the free electrons
in the metal wire to move rapidly back and forth.
THIS IS ALTERNATING CURRENT.
While the electrons don't go anywhere,
the energy wave or field does. If the wire is grounded, the current
will flow in that direction.
NO GROUND, NO FLOW
If there is no movement of electrons (current)
in the wire, there is no magnetic field. The faster and the greater the
number of electrons that move, the stronger the magnetic field.
Conversely, in a generator, the stronger
the magnet and faster it rotates, the stronger the electric current.
|THE RIGHT HAND RULE, the thumb points
in the direction of the flow and the curved fingers the direction of the
– when current flows, the magnetic field
is perpendicular to the flow of electrons, the magnetic field wraps around
the wire and goes counterclockwise.. the right hand rule
A.C. AND THE EMS
- Electrical energy waves MOVE AT THE SPEED
OF LIGHT like all other waves in the electro-magnetic spectrum.
--- As you watch waves come in on Lake
Michigan, there is energy and impact hitting the breakers. But the actual
water in each wave is not moving. The energy is in the oscillations
of the water up and down and that energy moves forward until the water
abruptly stops at the breaker and the kinetic energy is transferred to
the concrete in the walls or on the beach.
How is a magnetic field produced?
If electrons are not flowing in a wire,
is there a magnetic field?
How can A.C. electricity be induced in
Is there a magnetic field if there is
What is hypothesized to be responsible
for Earth's magnetic field?
Discuss what you know about the Van Allen
belts and how they are involved in Aurora Borealis.
How do the Van Allen belts protect the