Magnetism

1
Magnetism

• Similar to electric forces
• Magnetic Poles
• North and South Poles
• Historic Designations
• Like Poles Repel, Unlike Poles Attract
• Due to alignment of atoms in material

2
Magnetic Fields

• Similar to electric and gravitational fields
• Magnetic fields are produced by the MOTION of
  electric charges

3
Magnetic Fields

• Revolving electron produces field
• Spinning electron produces field
• In most atoms, combination of spins and orbits
  are in opposite directions
• The fields cancel each other out
• Some atoms, they dont cancel
• Iron, nickel, cobalt, aluminum

4
Magnetic Domains

• In iron, for example, field by an atom is so
  strong it causes neighboring atoms to arrange
  their spins and orbits to line up
• These clusters form magnetic domains
• Domains are randomly oriented in ordinary iron,
  nickel, etc.
• Can force them to line up with external field

5
Electric Currents Magnetism

• A moving charge produces a magnetic field

6
Electric Currents Magnetism
7
Electromagnetics

• Place a piece of unmagnetized iron in a coil of
  wire carrying a current
• Produce a strong magnetic field in the iron by
  lining up domains
• Makes the whole thing a very powerful magnet

8
Magnetic Forces and Charges

• If a charge isnt moving, a magnetic field has no
  effect on the charge
• Reciprocal kind of idea
• Moving charges produce magnetic fields
• Magnetic fields apply a force to a moving charge

9
Magnetic Forces and Charges
10
Magnetic Forces and Charges
11
Magnetic Forces and Charges
12
Meters

• Use a compass needle (magnet)

13
Meters
14
Motors
15
Electromagnetic Induction
16
Electromagnetic Induction
17
Electromagnetic Induction
18
Electromagnetic Induction
19
Electromagnetic Induction

• Faradays Law
• The induced voltage in a coil is proportional to
  the number of loops, multiplied by the rate at
  which the magnetic field changes within those
  loops.
• The amount of current depends on the resistance
  of the wire
• Changing magnetic field in a loop is key!!

20
Electromagnetic Induction

• Traffic light control (buried loops)
• Airport Security Systems
• Mag strips on credit cards
• Tape Recorders
• Computer Hard Drives

21
Generators
22
Generators
23
Power Production
24
Transformers
25
Transformers

• The more turns, the more voltage induced
• Step-up Transformer has more turns in secondary
  than in primary
• Step-down Transformer has more turns in primary
  than in secondar

26
Transformers

• Energy Conservation
• Power In Power Out

27
Field Induction

• An electric field is induced in any region of
  space in which a magnetic field is changing with
  time
• A magnetic field is induced in any region of
  space in which an electric field is changing with
  time
• Let there be light!!!