Legend

1
Legend
-White background is for Teacher to see as
instructions. -Blue back ground is for the
Student to see
2

• My presentation is more gear toward upper level
  high school physics student (i.e. Physics 11,
  Physics 12 and Physics 12 AP).

3
Materials needed for the demonstrations
Materials needed for the construction of the demos

• Pliers
• Sand paper
• Glue gun

Materials needed for the demos. Instructions will
be given in later slides

• 1 Cathode ray tube demo
• Cathode ray tube set

• 3 Ferromagnetic levitation
• borrow a levitation device from a year 2
• Mechanical Engineering 2006 friend

• 2 Battery demo
• 9V battery
• thin copper wires
• rubber band
• a neodymium magnet
• (order online _at_ www.grand-illusions.com/toyshop
  or ebay)

• 4 Diamagnetic levitation
• 4 neodymium magnets
• a piece of pyrolytic carbon

• 5 Maglev train
• Strong magnetic strips
• thin plexiglass
• the support track

4
Electromagnetism

• University of British Columbia
• Physics 420
• By Jason Cheung

5
What is a Field?

• A region of space characterized by a physical
  property having a determinable value at every
  point in the region
• Examples gravitational field, Electric field
  ,and magnetic field

6
Explanation of Field (1) (for slide 5)

• This means if we put anything appropriate in a
  field, we can then calculate something out of
  that field
• Before going further with Electric field and
  Magnetic field, mention there are something
  called the Electric and Magnetic field. Use
  gravitational field as a start, because G-field
  the most easy to understand
• Link Electric field and Magnetic field after
  explaining the Gravitational field

7
Gravitational Field

• Defined as

A acceleration
G gravitational constant
r distance to the center of the big
object
m mass of big object
8
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9
Explanation of Field (2)(for slide 8)

• If we put Bob in the gravitational field, we can
  calculate the Force acting on him by the Earth.
  He will follow the gravitational field lines and
  fall to the surface of the Earth.
• Essentially, if we put anything that has a mass
  in the Gravitational field, we can calculate that
  something I mentioned before. That something
  is the gravitational force in this case.
• Emphasize that we determine different kinds of
  force with different kinds of field. This can
  bridge to Electric and Magnetic Field on
  following slides.

10
Electric Field

• Electric field is defined as the electric force
  per unit Charge
• It is the surrounding charges that create an
  electric field

E Electric Field F Electric Force q Charge
E is measure in Force/Coulomb
11
Explanation of Electric Field (E-field) (for
slide 10)

• 0 Explain what is a charge, q
• - They should have enough Physics to know what
  is a /- charge is
• - Opposite charges attract each other and Like
  charges repel each other
• 1 Explain E is defined as F/q
• - If we put a /- (positive or negative) charge
  in a electric field, the /- charge will
  experience a force. This force is called
  Electric Force
• - (IMPORTANT!!) Recall from G-field. G-field
  requires an object with a MASS to have a force.
  E-field requires a /- charge to have a force
• 2 How do you draw the E-field lines with
  different charges?
• - Electric field lines always comes out of the
  positive charge into the negative charge
• - Negative charge always absorb the E-field
  lines

12
Explanation of Electric Field (E-field) (for
slide 10)

• 3 What direction is the electric force?
• - The direction of the Electric force is
  parallel to the electric field.
• - Look at the POINT P on the diagram on slide
  10. The arrow in the diagram represents the
  direction of the electric force
• Q What is the charge, positive or negative,
  if the direction of the force is pointing
  outward like in the diagram on slide 10
• A Positive because it is point away from the
  stationary positive charge
• Q What is the charge, if the direction of the
  force on the diagram switched??
• A Negative charge

13
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14
Cathode Ray Tube Demo (CRT)
Instruction and explanation for the CRT Demo
1 Turn on the Power supply and Electric plate
controller, and wait and calibrate the electrons
to the center of the screen 2 Adjust the
electric plate by turning the X knob or the Y
knob. This is to demonstrate that the electric
plate can control where the electron will hit on
the screen. Questions and Fun facts Q What do
you think is the application of a CRT and what do
the electric plates do in the CRT? A Our OLD
TV (before LCD and Plasma) use this technique to
view images on our TV!
15
Magnetic Field

• Magnetic field is a field that exerts a force on
  a moving charge
• A magnetic field can be caused either by another
  moving charge or by a changing of electric field
  or magnetic dipoles of materials

16
Explanation of Magnetic field(for slide 15)

• In order to have a magnetic force, we need a
  moving /- charge.
• Magnetic field lines come out of N and go into S
  (see diagram on slide 15)
• Emphasize the 3 components to produce a magnetic
  field
• 1 Moving /- charge
• 2 Changing of E-field
• 3 Dipole of material (see diagram to explain)
  

17

• Magnetic Field is measure in Tesla

A simple formula to calculate Magnetic Field
B magnetic field F Magnetic Force Q
charge V velocity of the moving charge
18
Explanation of Magnetic field cont(for slide 15)

• The unit of Tesla is a very SMALL unit
• - Earth magnetic field has around 10(-5) Tesla
  
• - A very good Ferromagnet has around 0.5 to 1
  Tesla
• It is very hard to make material that has a very
  strong magnetic field, and I will explain it in
  more detail later
• Since I am doing a qualitative study on
  magnetism, I just gave them one of the most basic
  equation for magnetic force
• - Emphasize on the CROSS PRODUCT, it is not
  treated as a times operator. Velocity of a /-
  charge needs to be 90 degree to the magnetic
  field in order to have a magnetic force

19
Construction of Battery demo
Step two tie the ears onto the battery with
rubber band

• Material needed
• copper loop
• 9V battery
• rubber band
• copper ears x2

Copper loop
9V battery
Copper ears
Rubber band
Step three put the copper loop through the
holes on the copper ears
Step one pinch the cooper ears onto the battery
Finish product
20
Video of battery demo
Show Battery Demo video under Videos
21
Battery Demo
Instruction of how to use the battery demo 1
Set up device as above 2 Bring the neodymium
magnet close to the loop 3 Give a kick start
for the loop by flicking it Things to tell the
students - Without the magnetic field, the loop
will no move - It is due to torque provided by
the magnetic force so that the loop will go round
and round
22
Extra interesting topic for the battery demo

• Q What is going on with the battery?
• Answer The permanent magnets exert forces on the
  electrical currents flowing through the loop of
  wire. When the loop of wire is in a vertical
  plane, the forces on the top and bottom wires of
  the loop will be in opposite directions. These
  oppositely directed forces produce a twisting
  force, or torque, on the loop of wire that will
  make it turn. Why is it so important to sand half
  of one projecting wire? Suppose that the
  permanent magnets are mounted with their north
  poles facing upward. The north pole of the
  permanent magnet will repel the north pole of the
  loop electromagnet and attract the south pole.
  But once the south pole of the loop electromagnet
  was next to the north pole of the permanent
  magnet, it would stay there. Any push on the loop
  would merely set it rocking about this
  equilibrium position. By sanding half of one end
  of the wire, you prevent current from flowing for
  half of each spin. The magnetic field of the loop
  electromagnet is turned off for that half-spin.
  As the south pole of the loop electromagnet comes
  closest to the permanent magnet, the un-sanded
  wire turns off the electric current. The inertia
  of the rotating coil carries it through half of a
  turn, past the insulating paint. When the
  electric current starts to flow again, the
  twisting force is in the same direction as it was
  before. The coil continues to rotate in the same
  direction.

23

• Charge moving in a magnetic field obeys the Right
  Hand Rule
• There are two types of RHR
• Right Hand Rule 1
• Right Hand Rule 2

24
Right Hand Rule 1

• The thumb represents the velocity of which the
  charge is going
• The remaining fingers tell you the direction of
  the magnetic field
• example

25
Right Hand Rule 2

• I direction of the charge
• B direction of the Magnetic Field
• F Force act on the charge
• Palm Push Positive (Remember!!)

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27
Slide 22

• The two diagrams show the path of a moving
  electron in a magnetic field
• Use RHR 2 to verify the path of the electrons in
  the diagrams are correct

28
Right Hand Rule Question

• Put a Ferro magnet (N or S) close the turned on
  CRT from the side.
• Note that the electron beam will either go upward
  or downward
• Q What is the magnetic field (N or S) on the
  side facing the CRT?
• A It depends on which side I put my magnet
  close to the CRT, but I just used RHR 2 to
  identified the N or S field on the Ferro magnet

29
Magnetism

• What is magnetism?
• Magnetism is one of the phenomena by which
  materials exert an attractive or repulsive force
  on other materials.
• What causes magnetism in material?
• It is the unpaired electrons in the electron
  orbit cause magnetism

• example of pair and unpaired
• N is unpaired,
• O is paired (one of them)

30
Remember SPDF?? (Chem 11)

• Electrons fall into electron shell according to
  Hunds rule.
• Examples

31
Explanation of Magnetism (for slide 29 and 30)

• 1 Explain what are paired and unpaired electrons
  
• 2 Recall their Chemistry 11, SPDF, electron
  orbital  
• - Using Hunds rules and Pauli Exclusion
  Principle to place electrons into electron
  orbital
• - Practice placing electrons into their orbital
  using the diagram on slide 30

32
Nitrogen
-Electrons
-Protons and Neutrons
1s2
2p3
2s2
Right
Electron Configuration of Nitrogen
Wrong
Wrong
33
Explanation of Magnetism (for slide 32)

• Exercise using Hunds rule
• -use Nitrogen as an example the first electron
  configuration is right and the second and third
  examples of the electron configuration is wrong

34
There are four types of magnetism

• 1.Ferromagnetic
• 2.Paramagnetic
• 3.Diamagnetic
• 4.Ferrimagnetic (Not going to cover)

35
(for slide 34)

• Tell students that Ferrimagnetism is too hard to
  understand. They need some university level of
  Physics in order to understand it

36
Magnetism is Measure in Magnetic Susceptibility
(?m)
The more susceptibility of a material has, the
more magnetic property it processes
37
Explanation of Magnetic Susceptibility (for slide
36)

• Magnetic Susceptibility is to measure the
  magnetic property of a material
• Q What is the differences between some of the
  materials in the chart in slide 36?
• A They split off into three groups
• 1 negative value with small Magnetic
  Susceptibility
• 2 positive value with small Magnetic
  Susceptibility
• 3 positive value with relatively big Magnetic
  Susceptibility compare to above 1 and 2
• 4 0 Magnetic Susceptibility for Vacuum
  because vacuum does not contain any material

38
Ferromagnetic

• Any material that possess magnetization WITHOUT
  an external magnetic field is ferromagnetic
• large and positive susceptibility
• Examples of ferromagnetic materials

Cobalt (Co) Susceptibility 70
Iron (Fe) Susceptibility 200
39
Explanation of Ferromagnetic(for slide 38)

• Explain what is an external field
• - example current running through a solenoid
• They do not need an external field because these
  material produce their own magnetic field. Some
  ferromagnetic material does not produce their own
  magnetic field because the domain inside of the
  material do not align, which I will explain in
  slide 42.

40
Iron electron configuration
Fe 1s2,2s2,2p6,3s2,3p6,4s2,3d6
Ar 1s2,2s2,2p6,3s2,3p6 Ar Core
Fe Ar,4s2,3d6
Ar
-The electrons seems to align spontaneously -Pure
quantum mechanics effect
41
Explanation of Iron (for slide 40)

• Another exercise to fill in the electrons in the
  electron orbital of Iron.
• Discuss that there are four unpaired electrons in
  the 3d orbital
• 1 This is one of the reasons why Iron can
  produce its magnetic field
• 2 The electrons seems to align spontaneously
  due to Quantum Mechanics effects

42
Why are some Ferromagnetic doesnt attract one
another?

• Has to do with the magnetic domain of the material

43
Explanation of domains of material(for slide 42)

• Diagram on the left shows the domains of the
  material do not align. This causes the magnetic
  field of the material cancel each other,
  therefore it cannot produce its own magnetic
  field
• Diagram on the right shows the domains of the
  material do align. Therefore, it can produce a
  magnetic field on its own 

44
Ferromagnetic material demo

• Material needed
• - neodymium magnet
• - couple of paper clips
• Instructions
• 1 Show them the paper clips do not attract to
  any material even though they are ferromagnetic
  (domains are not align).
• 2 Attract one of the paper clip to the
  neodymium magnet
• 3 use the paper clip that is on the neodymium
  magnet to attract another paper clip
• Q How come it attracts now?
• A The neodymium magnet help align the domain
  in the paper clip
• 4 Gently remove the neodymium magnet and show
  that the paper clip can still attract to each
  other
• Q Why?
• A It stays align until you pull them away

45
Paramagnetic

• Any material that possess magnetization (i.e.
  attraction with other magnetized material) WITH
  an external magnetic field is paramagnetic
• small and positive susceptibility
• Examples of paramagnetic materials

Aluminum Al Susceptibility 2.210-5
Platinum Pt
46
Paramagnetic material demo(for slide 45)

• Try to attract an aluminum can with a neodymium
  magnet. It cannot
• Q Why?
• A It is because of the Magnetic Susceptibility
  of paramagnetic materials are too weak compared
  to Ferromagnetic

47
Aluminum electron configuration
Ne.3s2.3p1
What is the differences between the two?!
Compare to Iron (Fe)
Ar
Fe Ar,4s2,3d6
the dipoles do not interact with one another and
are randomly oriented in the absence of an
external field due to thermal agitation,
resulting in zero net magnetic moment
48
Paramagnetic and Ferromagnetic Demo (magnets and
levitation)
Instructions of how to use the levitation device
1 Set up the device 2 Place orange stud with
the magnet side facing away from the solenoid 3
Place the stud so you can feel the solenoid is
attracting the stud 4 Gently remove your hand
so the device and do its work Explanation of how
it works - solenoid provide the magnetic field,
so the magnet will attract upward (para and
ferromagnetic property). - detector in the
bottom is to sense if the stud is moving up or
down. If it moves too high, the detector will
cut the current so the stud will come back down
by gravity. If it moves too low, the detector
will send current in the solenoid to generate a
magnetic field, so the stud will go up again by
the attraction between the magnet and magnetic
field
49
Video of ferromagnetic levitation
Show Ferromagnetic levitation video under Videos
50
Diamagnetic

• very weak and negative susceptibility to magnetic
  fields.
• Negative susceptibility repel against magnetic
  fields (diamagnetism)
• Positive susceptibility attract to magnetic
  fields (para ferromagnetism)

51
Diamagnetism

• Examples of diamagnetic materials

Gold
Human (mostly)
Copper
52
Diamagnetic Levitation Demo

• Instructions of how to use the magnets
• 1 Set up the magnets
• 2 Gently place the pyrolytic carbon in the
  middle of the four magnets

53
Applications of Magnetism
MRI (magnetic resonance images)
Superconductors
54
Application of Magnetism(for slide 53)

• Magnetic Resonance Images (MRI)
• - These machines can produced up to 7 Tesla to
  make very good images of the body
• Q How to produce a strong magnetic field ?
• A Build a giant solenoid
• Q What is the problem with producing a strong
  magnetic field
• A 1 Material cannot stand the magnetic
  force with the magnetic field resulting in
  collapsing the material
• 2 High velocity of current running through
  the solenoid produce a lot of heat. This can
  result in melting the solenoid if the magnetic
  field is too strong
• Super conductors
• - superconductors are very useful because it
  does not have any resistant with other material
  
• - all superconductors are diamagnetic
• Animals
• - Animals such as sharks and turtles use the
  Earth magnetic field to detect their position
  and direction (Research has not been finished, a
  few published paper support this theory)

55
Applications of Magnetism

• Maglev Trains

56
Maglev train demo

• Instruction of how to use the Maglev train
• 1 Set up the train track
• 2 Place the train onto the track
• 3 Push the train
• Discuss the problems that the demo had
• - too much friction from the side of the train
  because this is a ferromagnetic levitated train
  (solution is discussed in the next slide).
  Therefore, the train will move side to side
  causing friction with the track
• - human generated power

57
Application of Magnetism cont(for slide 55)

• WHY?
• Q why do people invent Maglev trains?
• A Less friction than trains with wheels
  because it does not need wheels to run
• HOW?
• - first it levitates using superconductors
• Q Why do we need superconductors to levitate,
  why cant we use ferromagnetic material like the
  train in the demo?
• A The problem with using ferromagnetic
  material to levitate the train is because
  ferromagnetic material will tend to want to
  align itself with the opposing field. Therefore,
  the train will be unstable moving right and left
  (i.e. like the train in the demo). The good
  thing about superconductors is because they are
  diamagnetic. They will always oppose a magnetic
  field, so they will not move out of the track
  trying to align with the field like
  ferromagnetic materials

58
Application of Magnetism cont(for slide 55)

• After the train is levitated, the train can move
  forward by the magnetic coil from the side. These
  coil can flip from N to S and vice versa to
  attract and repel against the magnets on the
  train (the magnets on the train is fixed and
  cannot be flipped.