Download I. Characteristics of Magnets - Otterville R

Ch. 14 - Magnetism
I. Characteristics of Magnets
 Magnetism
 Magnetic poles
 Magnetic field
 Magnetic domain
A. Magnetism
 Magnetism
 force of attraction or repulsion between
unlike or like poles
 due to the arrangement of electrons
 closely related to electricity
B. Magnetic Poles
 Magnetic Poles
 like poles repel
 unlike poles attract
 a broken magnet creates new poles
C. Magnetic Field
 Magnetic Field
 area around a magnet where magnetic
forces act
 field lines show direction of field (NS)
D. Magnetic Domain
 Magnetic Domain
 groups of atoms with aligned magnetic
poles
domain
 in a magnetized object, domains are all
aligned
Ch. 14 - Magnetism
II. Uses of Magnetic Fields
 Electromagnet
 Speaker
 Motor
A. Electromagnet
 Electromagnet
 strong, temporary magnet formed when
current is passed through a coil of wire
surrounding an iron core
 acts like a bar magnet when current is on
B. Speaker
 Speaker
 electrical energy  mechanical energy
 wire coil moves back &
forth as its magnetic
field interacts with the
field of a fixed magnet
 forced vibration causes
the cone to move 
sound
C. Motor
 Motor
 electrical energy  mechanical energy
 electromagnet
rotates between
the poles of a fixed
magnet
 commutator
reverses the poles
of the e’magnet
C. Motor
armature & commutator
assembled motor
brushes & wires to battery
field magnet
Ch. 14 - Magnetism
III. Producing Electric Current
 Electromagnetic Induction
 Electric Generator
 DC & AC
 Transformer
A. Electromagnetic Induction
 Electromagnetic Induction
 producing a current by moving a wire through a
magnetic field
 some microphones
work just like minispeakers in reverse
Coil
 sound waves cause
coil to move  current
Dynamic Microphone
B. Electric Generator
 Electric Generator
 mechanical energy  electrical energy
 armature is
rotated between
magnet poles
 magnetic field
induces a
current in the
wire coil
GENERATOR
MOTOR
B. Electric Generator
 Hydroelectric Dam
 PE of lake water is
converted to KE
 mechanical KE
turns the generator
shaft which creates
electrical energy
C. DC & AC
 Direct Current (DC)
 current flows in one direction
 dry cells
 Alternating Current (AC)
 current reverses its direction
at regular intervals
 electrical outlets
D. Transformer
 Transformer
 increases or decreases AC voltage
 primary coil AC produces a magnetic field that
induces AC in the secondary coil
 voltage ratio = ratio of turns in each coil
D. Transformer
 Step-up Transformer
 increases the voltage
 more turns
 power plants
 Step-down Transformer
 decreases the voltage
 fewer turns
 household appliances
(hairdryers, etc.)
Ch. 15 - Light
I. Electromagnetic Radiation
 EM Radiation
 EM Spectrum
 Types of EM Radiation
A. EM Radiation
 Electromagnetic Radiation
 transverse waves produced by the
motion of electrically charged particles
 does not require a medium
 speed in a vacuum = 300,000 km/s
 electric and magnetic
components are
perpendicular
A. EM Radiation
 Photons
 tiny, particle-like
bundles of radiation
 absorbed and released
by electrons
energy increases with
wave frequency
B. EM Spectrum
long 
short 
low f
high f
low
energy
high
energy
C. Types of EM Radiation
 Radiowaves
 lowest energy EM radiation
C. Types of EM Radiation
 Radiowaves
 FM - frequency modulation
 AM - amplitude modulation
Microwaves
penetrate food and vibrate
water & fat molecules to
produce thermal energy
C. Types of EM Radiation
 Infrared Radiation (IR)
 slightly lower energy than
visible light
 can raise the thermal energy
of objects
 thermogram - image made by
detecting IR radiation
C. Types of EM Radiation
 Visible Light
 small part of
the spectrum
we can see
 ROY G. BIV colors in order
of increasing
energy
red
R O Y
G.
orange
green
yellow
B
blue
I
indigo
V
violet
C. Types of EM Radiation
 Ultraviolet Radiation (UV)
 slightly higher energy than visible light
 Types:
• UVA - tanning, wrinkles
• UVB - sunburn, cancer
• UVC - most harmful,
sterilization
C. Types of EM Radiation
 Ultraviolet Radiation (UV)
 Ozone layer depletion = UV exposure!
C. Types of EM Radiation
 X rays
 higher energy than UV
 can penetrate soft tissue,
but not bones
C. Types of EM Radiation
 Gamma rays
 highest energy
EM radiation
 emitted by
radioactive atoms
 used to kill
cancerous cells
Radiation treatment using
radioactive cobalt-60.