Upcoming Deadlines

Second Term PaperScience Fact or Cinematic Fiction?Due Tuesday, April 24th (Next week)100 points (50 points if late)

Homework #11 – Building a Scene in MayaDue Tuesday, May 1st (In two weeks)20 points (10 points if late)

For full schedule, visit course website:ArtPhysics123.pbworks.com

Pick up a clicker, find the right channel, and enter Student ID

Autodesk Maya

For homeworks #11 and #12 you will be using Maya, a 3D graphics program.

You can download a free 30-day trial version of Maya from the Autodesk website.

Extra Credit Opportunity

Attend any event at 55th San Francisco International Film Festival, April 19–May 3, in San Francisco.

Present proof of you attendance (receipt, photos, etc.) for 10 points of extra credit.

Extra Credit Opportunity

Attend any event at the 6th Annual San Francisco Bay Area International Children's Film Festival, April 21–22, in downtown San Jose.

Present proof of you attendance (receipt, photos, etc.) for 5 points of extra credit. For info: www.cdm.org

Children’s Discovery Museum

Extra Credit Opportunity

Turn in your ticket receipt for ten points extra credit.

Hours: Wednesday-Monday: 10a.m.-6p.m

Admission: $15.00 for students

Location: 104 Montgomery Street

Inside The Presidio of San Francisco

Visit the Walt Disney Family Museum

http://www.disney.go.com/disneyatoz/familymuseum/index.html

Extra Credit Opportunity

Turn in your ticket receipt for ten points extra credit.

Hours: Tuesday-Sunday: 10a.m.-5p.m

Admission: $12.00 for students

Location: 3601 Lyon Street, SF 94123

Next to Palace of Fine Arts complex

Visit the Exploratorium in San Francisco.

www.exploratorium.edu

Survey Question

How many do you like using the blog for submitting your term paper:

A) Like it a lot

B) Like it

C) Neutral

D) Don’t like it

E) Don’t like it a lot

Review Question

Sparks from sparkler don’t burn skin because:

A)The sparks are bright but don’t have a high temperature.B)The sparks are high temperature but they don’t have much internal energy.C)The sparks have a very low conductivity.

Review Question

B) The sparks are high temperature but they don’t have much internal energy.

x x

The sparkler sparks have high temperature (5000 ºF) and high conductivity (burning iron) but are very small, with little mass.

By analogy, grains of sand that fall from a great height doesn’t have as much energy as a cannonball that falls a couple of feet.

. . . . . . . .

Review Question“Dry Ice” is made by freezingcarbon dioxide gas to -109 °F. The term dry ice comes from:

A) It’s not made with water so it’s “dry.”B) When it melts dry ice turns directly into a gas instead of a liquid.C) When you put dry ice into water it creates a dense fog that’s not damp.D) It was first discovered by the English physicist Sir Percival Martini Dry.

Review Question

Put dry ice into warm water to create dense fog of tiny water droplets; this is caused by the sudden release of CO2 gas as dry ice sublimates.

B) When it melts dry ice turns directly into a gas instead of a liquid.

This change of phase is called sublimation.

Effects Animation:Hot & Cold (cont.)

Convection

Heat transfer in a fluid often occurs mostly by convection.

Buoyancy causes warm air to rise, which carries thermal energy directly by its motion.

Demo: CandleVery HOT

Warm

Shadows revealrising air currents of hot air.

Rising hot air above a candle carries most of the heat generated by the burning flame.

Demo: Candle in a Tube

Candle stays light until the partition in the tube is removed. Why?

Partition allows hot air to rise, drawing in cold air (with fresh oxygen) to fuel the candle flame.

Without the partition, turbulence impedes the inflow and outflow.

Convection is disrupted because tube is narrow.

Explosions in Space

http://www.youtube.com/watch?v=z2jPCQbl0LcCamera is on the floor, looking up at the explosion

There’s no buoyancy in space so explosions expand but don’t rise.

Star Wars (1977)

RadiationLight has many different

wavelengths, most of which are not visible to the eye.

All light carries energy, thus transfers heat.

Heat LampHighly reflective fire proximity suits

Heat-Ray

The “heat-ray” first appeared in science fiction as the Martian weapon in H.G. Wells’ War of the Worlds (1898).

http://www.youtube.com/watch?v=gsXnK0ouTL8

War of the Worlds (1953) Mars Attacks! (1997)

High powered lasers are similar to H.G. Wells’ heat-ray.

Freeze-Ray

There’s no current technology to create a ray that removes energy from an object.

http://www.youtube.com/watch?v=TNjTW8ZBkuI

1968 Batman cartoon

Batman and Robin (1997)

Emission of Radiant Energy

All objects radiate light; higher the temperature the higher the light’s frequency.

At room temperature the radiated light is at frequencies too low for our eyes to see.

Special cameras are sensitive to this infrared radiation.

Attics in this house were kept warm for growing marijuana.

98º

75º

Predator (1987)Heat vision made the Predator a deadly adversary.

Beam splitter

Demo: Infrared Light

Digital cameras, such as in cell phones, are sensitive to infrared light, such as from a remote control or hot objects.

Effects Animation:Electricity

The Force

Electrical and magnetic phenomena are the inspiration for many special effects, such as the mysterious “Force” in the Star Wars epics.

Electric Charges and Forces

There are two types of charge:

positive charges and negative charges

REPEL REPEL ATTRACT

Like charges repel, opposite charges attract.

Charging by Friction/Contact

Electrons move easily so an object can become charged by rubbing electrons off the object’s surface.

• Brush your hair with a plastic comb.

• Walk across a carpet with plastic-soled shoes.

Electrons taken off of fur onto rubber rod

Demo: Electroscope

The “legs” of an electroscope separate when the electroscope is charged due to the repulsion of like charge on the two legs.

Charged ebonite rod deposits negative charge (electrons) onto electroscope.

“Legs”

Demo: Dial Electroscope

Alternative design for electroscope

Charged

Neutral

Demo: Van de Graff Generator

Van de Graff deposits large quantities of excess charge on its globe.

A person with long hair can become a human electroscope.

Repulsion also demonstrated with pie plates, Rice Krispies, etc.

Demo: Electric Pinwheel

Pinwheel turns as charge leaves the Van de Graff from the points at the tips of the spokes.

Van deGraff

ChargedAir molecules

Lightning Storms

Charge separates inside of thunderclouds.

The lower part of the cloud is negatively charged.

This induces a positive charge on the ground.

When the voltage difference is high enough, a lightning bolt can occur.

Demo: Franklin’s Bells

Benjamin Franklin invented this to detect the approach lightning storms.

Reminder:Start cooking

hotdog

Plastic Insulators

Plastic insulation on step of van de Graff and charge wand keep charge from leaving the metal balls.

Plastic insulation on wire prevents charge to leave wire except at the ends, where the conducting metal is exposed.

Demo: Tesla Coil

Air is an insulator but at high voltages it can conduct electricity as lightning.

PortableTesla coil

Tesla Coils

Very high voltages achieved with large Tesla coils.

Homemade, backyard modelFry’s Superstore, Fremont CA

Faraday Cagehttp://www.youtube.com/watch?v=Zi4kXgDBFhw

Demo: Resistance of Water

Pure water has very high resistance; impurities, such as salt, lower resistance.

PowerSupply

CU

RR

EN

T

Light Bulb

Ammeter

SaltyWater

When salt dissolves the sodium and chlorine atoms are charged (ions). These mobile charges carry the current in the water.

Ohmic Heating

Flowing electrons strike atoms in a conductor, heating the material.

Toasterhttp://www.youtube.com/watch?v=OGezvYafezE

Hellboy (2004)

Demo: Ohmic Cooking

An electric current running through a hot dog generates enough heat to cook it.

Strange light show when using a pickle in place of hot dog. Similar to sodium lamp discharge.

Jacob’s Ladder

Ohmic heating of the air creates an electrical discharge visible.

Jacob’s Ladder

Spark begins near the bottom, where the gap is small.

The current heats the air in the gap, causing it to rise since hot air is buoyant.

Check out the 5 foot Jacob’s Ladder outside our classroom

Electrocution

Electrocution (death by electric shock) is usually due to ohmic heating of the internal organs of the body.

True or False

Electrocution

False

It is due to the disruption of the nervous system, especially that which controls the heart beat.

Nervous SystemNervous systems in animals use

electrical currents to signal the contraction and relaxation of muscles.

Frog leg jumps when electrical current passes through it.

Presto (2008)

Common visual gag is the uncontrollable twitching of a person’s muscles.

Notice Jacob’s Ladder in Presto’s hair

http://www.youtube.com/watch?v=mw-fs19kTGM

Sherlock Holmes (2009)

The electric shock does not exert a force, rather it causes muscles to contract; this scene is not realistic.

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.

Current (A) Effect

0.001 Can be felt

0.005 Is painful

0.010 Causes involuntary muscle contractions (spasms)

0.015 Causes loss of muscle control

0.070 If through the heart, serious disruption; probably fatal if current lasts for more than 1 s

Effects of Electric Shock on Human BodyCurrent depends on the voltage and on electrical resistance.

When dry, skin’s resistance around 100,000 .

Resistance drops as low as 100 when wet and salty.

Frankenstein (1931)

Electricity brings Frankenstein’s monster to life in the 1931 horror classic yet it’s not mentioned in the original book, written in 1818 by Mary Shelley.

Bolts for electrical contact

http://www.youtube.com/watch?v=8H3dFh6GA-A

Next LectureLighting & Optics

Part INext Week’s Assignment:

Second Term Paper

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