Upcoming Deadlines

Second Term Paper – Science Fact or Cinematic Fiction?Due Wednesday, November 17th (Next week)100 points (50 points if late)

Homework #11 – Building a Scene in MayaDue Wednesday, November 24th (Day before Thanksgiving)20 points (10 points if late)

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

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Survey Question

How much experience do you have using AutoDesk Maya?

A) A lot of experienceB) A little experienceC) Never used it but know of itD) Not familiar with it at all

Review Question

Which of these is not a mechanism for heat transfer?

A) ConductionB) RadiationC) ReductionD) Convection

Heat Transfer

C) Reduction

Conduction

Convection

Radiation

Review QuestionFill in the blanks:

Two objects with positive charge _______ each other and two objects with negative charge _______ each other.

A)Attract … RepelB)Repel … AttractC)Attract … AttractD)Repel … Repel

+ +

- -

Electric Charges and Forces

D) Repel … Repel

REPEL REPEL ATTRACT

Like charges repel, opposite charges attract.

Note that by Action/Reaction, the force on each object is always equal in magnitude, opposite in direction.

Review QuestionFlowing electrons strike atoms in a

conductor, heating the material.This type of heating is named after:A)André-Marie AmpèreB)Nicola TeslaC)Thomas EdisonD)Georg OhmE)Alessandro Volta

Toaster

Ohmic HeatingGeorg Simon Ohm (1789 –1854) was a German physicist. As a high school teacher, Ohm began his research with the recently invented electrochemical cell, invented by Italian Count Alessandro Volta.

Using equipment of his own creation, Ohm determined that there is a direct proportionality between the potential difference (voltage) applied across a conductor and the resultant electric current – now known as Ohm's law.

Ohmic heating is also called Joule heating, first studied by James Prescott Joule in 1841

Georg Ohm

Effects Animation:

Electricity & Magnetism

Part 2

WARNINGStrong magnets will be passed around the room.

Keep these magnets away from iPods and laptops (especially my laptop)!

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 ShockThe damaging effects of shock are the result of

electrical 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

Magnetohttp://www.youtube.com/watch?v=rKc4BWvWtuM

The majority of the animation and lighting in this scene was done in Maya.

Magneto, the villain in the X-men movies, controls the force of magnetism.

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.

Iron Ore

Ferromagnetic Metals

Ferromagnetic metals have similar atomic structure.

Iron, Cobalt, Nickel

Spin of the electron in these metals produces a net magnetic fieldMany ferromagnetic alloys (blends of metals)

Demo: Magnetism & MoneyMost 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

Buffalo nickels are 25% nickel metal, which is ferromagnetic

Some Euro coins contain steel

Iron is in the ink used in US paper currency to avoid counterfeiting.

Magnetizing Iron

S N

S N

StrongMagnet

StrongMagnet

Magnetic domains can be induced to align by an external magnetic field.

N

Demo: Magnetizing Iron

Magnetic domains 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.

When the strong magnet is removed, most of the domains un-align and nail lose most of their magnetization.

Demo: Demagnetizing Iron

Iron nail is attracted to the large magnet due to alignment of domains in the nail.

Heat the nail to a high temperature and the domains become randomized so the nail is no longer attracted to the magnet.

Magnets & Wile E. CoyoteWile E. Coyote is surprised when a big metal can of TNT comes flying in, pulled in by his magnet.In reality, the force of the can on the magnet is just as strong as the pull of the magnet is on the can of TNT.

True or False?

Magnets & Wile E. Coyote

True.

Another example of action/reaction principle (Newton’s Third Law).

Action force is magnet pulling TNT can.Reaction force is TNT can pulling magnet.

From “Zipping Along”

Demo: Electromagnets

Electromagnet created by passing current through a coil of wire.

Electromagnet is stronger when an iron bar is inserted within the coil.

Connect to battery or power supply

WireCoil

N

S

Iron Bar

Loudspeakers

Loudspeaker has a membrane but oscillations are created by variations in electrical current, which cause an electromagnet to be pulled towards and away from a second, permanent magnet.

These oscillations cause the membrane of the loudspeaker to vibrate with the same frequency as the oscillations in the electrical current.Headphones work essentially the same way, they’re just smaller.

Earth’s Magnetic FieldThe configuration of the

Earth's magnetic field resembles a strong bar magnet located near the center of the Earth.

The magnetic South pole is near the geographic North pole (so North pole of compass attracted towards Northern direction).

There isn’t an giant underground magnetized chunk of iron; Earth’s interior is simply too hot.

N

S

Origin of Earth’s Magnetic Field

Earth is an electromagnet with electric currents deep below the surface.

Moving charges, looping around within the molten part of the Earth, create the magnetic field.

These currents are possibly the result of thermal convection rising from the central core combined with the rotation of the Earth about its axis.

Demo: Electric Motor

Can create an electrical motor by passing a current through a set of electro-magnets mounted on a rotating shaft.

Current inCurrent out

Electro-magnets

Electric Motor, AnalyzedElectromagnet

mounted on a shaft with opposing magnets on each side.

Current direction always such that electromagnet is repelled, causing shaft to turn.

N SN S

N S

N S

Current

Current

Demo: Magnetic Force & Current

Moving charges in an electric current experience a force due to magnetic field.

Demo: Crooke’s Tube

Electron beam in a Crooke’s tube is deflected when a magnet is brought near the tube.

Apr 20, 2023

Television Tube

Electron beams, deflected by magnetic fields, are used to create TV images.

Electromagnets

Demo: Magnets & TV sets

N

S

Picture on a TV set is distorted by presence of a magnet since picture formed by an electron beam.

Warning: Strong magnets can permanently damage a television or a computer.

Demo: Magnet Induces CurrentVoltage and current are induced when a magnet

moves towards or away from a coil of wire.Faster the magnet’s motion, the greater the

induced current.

Demo: Electric Generator

Turn the shaft by hand and as the coils pass the magnets a voltage is induced.

DC current is generated.

Magnet

Magnet

Coils

DC Output

SHAFT

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

EMP (ElectroMagnetic Pulse)A strong, rapidly fluctuating magnetic pulse can

induce high voltage, causing strong currents.

In 1962, a nuclear test in the Pacific produced an EMP that knocked out 300 streetlights and telephone service in the Hawaiian islands, 900 miles from the explosion. Starfish Prime, as seen from Honolulu

Call of Duty: Modern Warfare 2 (2009)

In the “Second Sun” campaign mission a nuclear missile creates a high-altitude EMP.

Streetlights explode, helicopters fall out of the sky, and electronic equipment on weapons is “fried.”

Next LectureLighting & Optics

Part I

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