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MAGNETS. AND ELECTROMAGNETISM. MAGNETISM. FOUNDATIONS OF SCIENCE. MAGNETISM. Electric currents or the movement of electrons in an atom will create the property of magnetism in an objec t -Stop and Think- Write what you know about magnets right now. DISCOVERY OF MAGNETS.

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magnets

MAGNETS

AND

ELECTROMAGNETISM

magnetism

MAGNETISM

FOUNDATIONS OF SCIENCE

magnetism1
MAGNETISM
  • Electric currents or the movement of electrons in an atom will create the property of magnetism in an object

-Stop and Think-

  • Write what you know about magnets right now
discovery of magnets
DISCOVERY OF MAGNETS
  • A SPECIAL STONE WAS DISCOVERED ABOUT 2,000 YEARS AGO IN GREECE IN THE REGION OF MAGNESIA
  • IT ATTRACTED IRON AND WAS CALLED MAGNETITE
  • ABOUT 1000 YEARS AGO, IT WAS NOTICED THAT A HANGING MAGNET ALWAYS POINTED TO THE NORTH STAR AND WAS CALLED LODESTONE
magnets are
MAGNETS ARE…..
  • A magnet is a material that attracts iron or matter that contains iron.
  • There are some naturally occurring magnets, for example certain types of rock are magnetic
  • Magnets will be attracted to or repelled by another magnet (north/south poles)
  • Magnets will always point North when allowed to swing freely
magnetic fields
MAGNETIC FIELDS

Magnetic fields are the area of force around a magnet

Magnetic fields are shown in a diagram with magnetic field lines

Magnetic field lines always leave the North Pole and enter the South Pole

Magnetic field lines never cross

magnetic field lines
MAGNETIC FIELD LINES
  • TRACE THE SHAPE OF THE MAGNETIC FIELD
  • LINES SPREAD OUT FROM ONE POLE AND RETURN TO THE OTHER POLE
  • ARE MORE CONCENTRATED WHERE THE FORCE FIELD IS STRONGER
  • THE FIELD IS STRONGER AT THE POLES OF THE MAGNET
slide11

Restate 3 facts about magnets.

  • What are magnetic field lines and how are they drawn?
magnetism and electrons
MAGNETISM AND ELECTRONS
  • MAGNETS ARE MADE UP OF ATOMS.
  • ATOMS CONTAIN ELECTRONS.
  • ELECTRONS SPIN ON THEIR OWN AXIS AND REVOLVE AROUND THE NUCLEUS OF THE ATOM.
  • THE MAGNETIC FIELD IN MOST ATOMS IS DUE TO THE MOTION OF ELECTRONS.
magnetic elements
MAGNETIC ELEMENTS
  • THE MAGNETIC FIELDS OF TWO PAIRED ELECTRONS SPINNING IN OPPOSITE DIRECTIONS CANCEL EACH OTHER OUT.
  • SOME ELEMENTS CONTAIN ELECTRONS WHICH ARE UNPAIRED; THESE ARE Fe, Ni, and Co.
  • THE MAGNETISM OF THE ELECTRONS DOES NOT CANCEL OUT SINCE THEY ARE NOT PAIRED.
  • EACH ATOM OF Fe, Ni, and Co ACTS AS A TINY MAGNET.
magnetic interactions
MAGNETIC INTERACTIONS
  • North to North
  • North to South
  • South to South
slide16

Draw a diagram of an electrically stable atom

What is the significance of paired and unpaired electrons in the atom?

magnetic domains
MAGNETIC DOMAINS

1. DOMAINS ARE CLUSTERS OF MAGNETICALLY ALIGNED ATOMS

2. EACH CLUSTER HAS ATOMS WITH FIELDS POINTING IN THE SAME DIRECTION

3. WHEN DOMAINS ARE ALL ALIGNED IN THE SAME DIRECTION, THE MATERIAL EXHIBITS MAGNETISM

magnetic induction
MAGNETIC INDUCTION

1. A MATERIAL LIKE AN IRON NAIL CAN BE MAGNETIZED BY A STRONG MAGNET

2. IT WOULD CAUSE THE SCATTERED DOMAINS TO ALIGN TEMPORARILY

3. WHEN IT IS REMOVED FROM THE MAGNET, THE DOMAINS BECOME RANDOM AGAIN

magnetic reversals in crust
Magnetic Reversals in Crust
  • Evidence in the rocks shows that Earth’s magnetic poles have reversed.
  • The iron bits line up in an alternating pattern.
  • The alternating pattern demonstrates crust movement
when and why does it happen
When and Why Does it Happen
  • The iron contained in the molten magma lines up with Earth’s current magnetism
  • When magma turns to rock, the magnetic alignment is frozen in time providing a record
  • Could be caused by a change in motion of material at Earth’s core
analyzing the data
Analyzing the Data
  • Earth’s magnetic poles move slowly over time. The data in the table show the position of Earth’s magnetic north pole in specific years.
  • 1. What is the trend in the speed of the pole’s movement?
  • 2. What is the total distance the pole has traveled over the time shown
earth s magnetic poles
EARTH’S MAGNETIC POLES
  • BAR MAGNETS LINE UP SUCH THAT THE ARROW POINTS TOWARD THE EARTH’S MAGNETIC NORTH POLE
  • CURRENTLY OUR GEOGRAPHIC NORTH POLE IS A MAGNETIC SOUTH POLE
electromagnets
ELECTROMAGNETS
  • CONTAIN A MAGNET WHOSE FIELD IS PRODUCED BY AN ELECTRIC CURRENT
  • THE FIELD INTENSIFIED BY INCREASING THE CURRENT GOING THROUGH THE WIRE OR BY THE LOOPS IN THE WIRE.
electromagnets1
ELECTROMAGNETS
  • Created by electric current that travels through wires or coils wrapped around an iron core.
  • The core will

concentrate and

amplify the field

electromagnets2
ELECTROMAGNETS
  • THE MAGNETIC FIELD INTENSITY INCREASED WITH THE NUMBER OF COILS IN THE WIRE.
  • THE NUMBER OF COILS IS DIRECTLY PROPORTIONAL TO THE NUMBER OF PAPER CLIPS PICKED UP BY THE MAGNETIC FIELD
slide30

What is an electromagnet?

  • Explain the difference between a geographic north pole and a geomagnetic north pole.
permanent vs electromagnets
Permanent vs. Electromagnets
  • Permanent magnet is always magnetic
  • Retains properties even when it is not close to other magnets
  • Strength cannot be changed
  • Electromagnets can be turned on and off
  • Produced by the electric current and magnetized core
  • Strength can be hundreds or thousands of times larger than a permanent magnet and can be adjusted
applications of electromagnets
APPLICATIONS OF ELECTROMAGNETS

MANY DIFFERENT APPLICATIONS

common electromagnets
Common Electromagnets
  • Video Tapes
  • Computer Hard Drives
  • Credit Cards
  • Junk Yard Cranes
  • Generators
the right hand rule
The Right Hand Rule
  • You are able to tell which end is NORTH by following this rule.
  • If the coils are wrapped in the same direction as your right hand, then the thumb points NORTH