Transcript Slide 1

Upcoming Classes
Thursday, Oct. 11th
Special: Jeffrey Katzenberg Interview
Assignment due:
* None
Tuesday, Oct. 16th
Good Vibrations and Bad Oscillations
Assignment due:
* Topic & outline of second oral presentation or written paper
Jeffrey Katzenberg @ SJSU
No lecture on Thursday. Instead, I encourage you
to attend the interview of Jeffrey Katzenberg,
Head of DreamWorks Animation SKG Studios.
Producer for Shrek (I,II,III), Nightmare before
Christmas, Chicken Run, and many others.
Morris Dailey Auditorium (in Tower Hall)
Oct. 11th (Thurs.), 2:00-3:15pm
Upcoming Deadlines
Thursday, October 11th
Outline of second oral presentation or
written paper
Tuesday, November 6th
Second Set of Oral Presentations
Second term paper (if not presenting)
Oral Presentations (II)
The following persons will give oral presentations
on Tuesday, November 6th :
• Luttrell,Katherine
• Macdonald,Keith
• McDonald,Kathleen
• Mendoza,Jazmin
• Nguyen,Jennifer
• Nguyen,Linda
For everyone else, term paper is due on that date.
Extra Credit: SF Museum of Art
Visit San Francisco Museum of Modern Art and
see Abstract Expressionist paintings.
Turn in your ticket receipt ($7 for students). Worth
one homework assignment; deadline is Oct. 16th
Guardians of the Secret, Jackson Pollock, 1943
Extra Credit: San Jose Ballet
See a performance of San Jose Ballet in San Jose
Center for Performing Arts (Nov. 15th – 18th ).
Turn in your ticket receipt. Worth one homework
assignment or three quiz/participation credits.
Ramon Moreno in CARMINA BURANA
What Not To Do In Class
During class please do not:
• Surf the web
• Fart loudly
• Text message
All three are equally distracting to me
so your cooperation is appreciated.
Thank you.
Dissecting the iPod
WARNING
Strong magnets will be
passed around the room.
Keep these magnets away
from (working) iPods and
away from laptops
(especially my laptop)!
Apple iPod
Apple announced its first generation iPod in October 2001 as a Maccompatible product with a 5 Gigabyte disk drive that put “1000 songs
in your pocket.” This model’s display was black and white and the
control wheel physically turned. Price: $399
Current model (as of Fall 2007) is fifth generation; has a color screen,
touch sensitive wheel, and hard disk of 160 Gbytes. Price: $349
iPod Nano is similar
but with chip
memory replacing
disk drive;
iPod Shuffle is like
Nano but without
screen.
First Generation
Fifth Generation
Third Generation iPod Dissected
LCD Display
Battery
Front Panel
Disk Drive
Circuit Board
(on rear cover)
Fifth Generation iPod components are similar except for front panel buttons
iPod Circuit Board
The most complex element inside the iPod
is the circuit board, which is essentially a
small, specialized computer.
Explaining the details
of how this works
would take several
semesters, but let’s
look at a few basic
ideas behind electric
circuits.
Current
Water flows from the
reservoir of higher
pressure to the reservoir
of lower pressure; flow
stops when the pressure
difference ceases.
Water continues to flow
because a difference in
pressure is maintained with the
pump.
Electric Current
Just as water current is flow of water molecules,
electric current is the flow of electric charge.
In circuits, electrons make up the flow of charge.
ON
OFF
Electrical Resistance
Current depends not only on the voltage but
also on the electrical resistance of the
conductor.
Metals are good electrical
conductors due to unbound
electrons (they’re good heat
conductors for the same
reason).
Plastics are poor electrical
conductors (i.e., insulators).
Pattern printed in metal channels the
electrical currents in the circuit board.
Ohm’s Law
Relation between current, voltage, and
resistance is Ohm’s law,
(Current) =
(Voltage)
(Resistance)
Ampere is unit of current; symbol is A
Volt is unit of voltage; symbol is V
Ohm is unit of resistance; symbol is 
Nervous System
Nervous systems in animals
use electrical currents to
signal the contraction and
relaxation of muscles.
Frog leg jumps when electrical
current passes through it.
Conduction in Human Heart
The most important
electrical signal in our
body is the periodic signal
that contracts and relaxes
our heart muscle to pump
blood.
Without a constant flow of
blood the brain can suffer
permanent damage.
SA
AV
Electric Shock
The damaging effects of shock are the result
of current passing through the body.
Effects of Electric Shock on Human Body
From Ohm's law, current
depends on the voltage and
on electrical resistance.
Current (A)
Effect
0.001
Can be felt
0.005
Is painful
When dry, skin’s resistance
around 100,000 .
0.010
Causes involuntary muscle
contractions (spasms)
0.015
Causes loss of muscle control
Resistance drops as low as
100  when wet and salty.
0.070
If through the heart, serious
disruption; probably fatal if
current lasts for more than 1 s
Voltage Sources
Charges flow only when they are “pushed” or “driven.” A
sustained current requires a suitable pumping device to
provide a difference in electric potential—a voltage.
Aluminum
Lemon
Copper
Simple Chemical Battery
Simple Mechanical Generator
Chemical Battery
Batteries separate
positive and
negative charges by
using a chemical
reaction.
Chemical potential
energy is converted
into electrical
energy.
Rechargeable Battery
Eventually the battery’s chemicals are consumed
unless the reaction can be reversed by passing
a current into the battery.
Automobile battery is
recharged while the
gasoline engine is
running since the
engine powers a
generator that
produces a recharging
current.
Starting the car
Engine running
iPod Battery
The iPod uses a Lithium ion (Li-Ion) battery.
Lithium is a light metal with a high charge density.
Lithium ion batteries have
the advantage of being light
weight, rechargeable, loss of
charge is slow when not in
use, and may be shaped
into a flat, compact shape.
Direct & Alternating Current
Direct current (DC) is
current that flows in
only one direction.
Alternating current (AC)
is current that flows
back and forth with
alternating direction.
Ohmic Heating
Flowing electrons
strike atoms in a
conductor, heating
the material.
Toaster
DC vs. AC
Easy to produce small
DC currents using
batteries, which also
have low voltages.
For major power lines,
less ohmic heating if
high voltage AC
current is used
instead of DC.
iPod Hard Disk
Data is stored by magnetic recording of the platter’s surface.
Arm swings across the surface to write on different “tracks.”
Motor spins the platter so the arm can reach any point on the disk.
Motor
Platter
Arm
Magnetic Forces
General observations regarding magnets:
Iron (and a few other metals) are
ferromagnetic, which means they can
become magnetized.
Magnets attract ferromagnetic metals.
Two magnets can either attract or repel
each other depending on poles.
Magnetic Poles
Cow magnets
Two types of magnetic poles:
North (N) and South (S)
N
S
As with electric charges, like poles
(N&N, S&S) repel and opposites
(N&S) attract.
Unlike electric charges, cannot have
just a North or just a South pole
Magnetic poles are not electric charges
Magnets
N&S
on sides
Compass
needle is
magnet
Demo: Magnetic Fields
Magnetic field points
from South to North.
Iron filing act as tiny
compass needles,
outlining magnetic
field lines.
Magnet
Iron filings in clear oil
Inside the magnet, field lines
go North to South
Ferromagnetic Metals
Ferromagnetic metals have similar atomic
structure.
Spin of the
electron in
these metals
produces a
net magnetic
field
Iron, Cobalt, Nickel
Demo: Magnetism & Money
Most US coins are not made of ferromagnetic materials
but many other countries use iron steel in their currency.
Some pennies
were made of
steel during
World War II
Some Euro coins
contain steel
Iron is in the ink used in US paper
currency to avoid counterfeiting.
Buffalo nickels are
25% nickel metal,
which is
ferromagnetic
Magnetizing Iron
Magnetic alignment of iron atoms can be
induced by an external magnetic field.
S
N S
Strong
Magnet
Strong
Magnet
N
N
Demo: Magnetizing Iron
The atoms in iron nails are induced
to align by proximity of the strong
magnet
Each nail becomes itself a magnet,
which in turn magnetizes the nail
below it, forming a chain.
If the strong magnet is removed,
most of the alignment is lost so
the nails lose most of their
magnetization.
Electromagnets
N
Electric current in a coil of wire creates a
magnetic field similar to a bar magnet.
S
Current
passing
through
loops of
coiled wire
Demo: Electromagnets
Electromagnet
created by passing
current through a
coil of wire.
Electromagnet is
stronger when an
iron bar is inserted
within the coil.
N
Wire
Coil
S
Connect to
battery or
power supply
Iron Bar
Electromagnetic Induction
Voltage is induced whether the magnetic field of a
magnet moves near a stationary conductor or
the conductor moves in a stationary magnetic
field.
Demo: Magnet Induces Current
Voltage is induced when a magnet moves towards
or away from a coil, inducing a current in the coil.
Faster the magnet’s motion, the greater the
induced current.
Magnetic Recording
Write data by magnetizing
recording media (e.g.,
video tape, hard disk)
using electromagnets.
Data is read back using the
induced current produced
when magnetized media
moves past receiver coils
(reverse of writing data).
Hard disk
Electric Generator
Electric generator moves a conductor in a
magnetic field to produce voltage via
electromagnetic induction
Demo: Electric Generator
Turn the shaft by
hand and as
the coils pass
the magnets a
voltage is
induced.
DC current is
generated.
DC Output
S
H
A
F
T
Magnet
Magnet
Coils
Induction: No Free Lunch
Takes work to turn
the generator crank
to produce electric
current.
The faster we turn
the crank to
produce more
current, the more
difficult it is to turn.
More difficult to
push the magnet
into a coil with
more loops
because the
magnetic field of
each current loop
resists the motion
of the magnet.
Demo: Electric Motor
Can create an electrical motor by passing a
current through a set of electro-magnets
mounted on a rotating shaft.
Current out
Current in
Electro-magnets
Electric Motor, Analyzed
Electromagnet
mounted on a
shaft with
opposing magnets
on each side.
Current direction
always such that
electromagnet is
repelled, causing
shaft to turn.
Current
N
S
Current
N
S
Demo: Generator Becomes Motor
Pass a current into the generator and it
becomes an electric motor.
DC Input
Battery
Magnet
Magnet
Rotor
Spins
iPod Liquid Crystal Display
iPod’s display is
similar to a flatpanel computer
monitor or LCD
television.
We’ll discuss how
this works in a
future lecture when
we study the
properties of light.
Next Lecture
Katzenberg Interview
Remember:
Meet in Morris Dailey Auditorium
(in Tower Hall) from 2pm to 3:15pm