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Course: Physics 101, Conceptual Physics Fall 2004
This course attempts to give a broad introduction to the "rules of the game" of the physical universe; that is, to the exciting world of physics. While the course is basically non-mathematical, some knowledge of high-school algebra is pre-requisite, and algebra (such as solving simple equations, or using powers of numbers) will be used regularly. To understand physics, one MUST be able to express central concepts both in words and equations. Little calculational ability is expected, however.
Homework and Webassign: Each daily homework assignment consists of two parts, the set of Practicing Physics pages for the chapter and the chapter assignment from Webassign. The Practicing Physics pages for a given set of chapters will be due at the time of the quiz for those chapters. The schedule of dates for the Webassign assignments will be shown at the Webassign site.
Webassign: Due to budgetary cutbacks we are using a web-based homework system for this course. It is less than ideal, but does provide good coverage of the material. After you obtain your Webaccess student account, you will find that the Webaccess page is that which you will want to log into in order to do your homework assignment. However, I will continue to use the course syllabus at the class course page to indicate the schedule of lecture reading and quizzes. There are two parts to most of the Webassign sets. The questions from Part A receive fractional credit compared to Part B, and are answered generally by a text answer. Part B involve a calculated answer.
Extra credit: I will assign a number of problems on Webassign. Each problem specifies how many points that will be credited. Regular credit for a given assignment will be 20 points, including 5 points for completed Practicing Physics pages. However, there will be more than 15 points worth of problems assigned. Any extra points earned on an assignment will be credited towards your extra credit pool, to be used to bring up assignments to the maximum of 20 points per assignment where you may have received less than full credit. Unlike quiz and final scores, homework grades will NOT be strictly curved, as I expect that the median score on the homework to be considerably higher than if no extra credit were added..
Click on to jump to specific chapter:Ch 1, Ch 2, Ch 3, Ch 4, Ch 5, Ch 6, Ch 7, Ch 8, Ch 9, Ch 10, Ch 11, Ch 12, Ch 13, Ch 14, Ch 15, Ch 16, Ch 17, Ch 18, Ch 19, Ch 20, Ch 21, Ch 22, Ch 23, Ch 24, Ch 25, Ch 26, Ch 27, Ch 28, Ch 29, Ch 30, Ch 31, Ch 32, Ch 33, Ch 34
The syllabus closely follows the table of contents of Hewitt at least as of now - we cover one to two chapters of Hewitt a day. It is expected that most days you will read the chapter, do the Practicing Physics pages and the assignment at Webassign. At the end of each class there will be a brief in-class quiz, usually closely tied closely to what you did for homework. At the mid-point (Ch 1-5) and end of Part 1 (Ch 1-10), Part 3 (Ch 11-18), Part 4 (Ch 19 - 26) and Part 5 (Ch 27 - 34) there will be major multiple choice quizzes.
August 26-31: Introduction (s), About Science
For next time - Read Chapters 1 & 2, do the Practicing Physics pages for the two Chapters and the homework at WebAssign.net.[There are two HW parts to each day, the practicing Physics pages for the chapter and the WebAssign pages]
(The quiz on Tuesday will only cover the Practicing Physics pages - normally it would cover both parts of the HW)
names of neighbors, check with your neighbor
Physics - the basic science
Tries to explain (develop theories ) for physical phenomena of universe in mathematical terms that can then be tested experimentally, expresses results mathematically.
Math - requirement - algebra (equations) so I can write equation, use things like area of circle, circumference of circle, etc., Many physical phenomena most clearly understood by mathematical relationship. Use proportions - example of triangles to illustrate, then extension of triangles to size of earth, discuss Eratosthenes 235 BC 800 km Alexandria to Syene. shadow 1/8, so similar triangles, distance 1/8 radius, 8 X 800 = 6400 km radius.
- an idea to be tested. After a group of related hypotheses have been verified, they can form a theory.
Aug 31- Chapter 2 - Newton's First Law -Inertia
For next time - read Ch 3, do the Practicing Physics pages and the HW assignment at WebAssign.
Aristotelian physics; Copernicus,
Fixed universe, source of motion in object, geocentric vs heliocentric
Gailileo's inclined planes
Objects are lazy "Motion continues"
Newtons First Law: inertia
Net Force à motion
Equilibrium, support force, the moving earth.
Sept 2: Chapter 3 - Linear Motion
For next time - read Ch 4, do the Practicing Physics pages and the HW assignment at WebAssign
Motion is relative
Speed = Distance/time (think miles/hour, or miles per hour)
Instantaneous vs. average
Or: speed = (total distance covered)/(time interval)
or v= d/t
speed equals the rate of change of distance
(that is, change in distance, per second)
In physics, velocity is defined precisely as giving the speed and the direction. It what we call a vector. Again, have average and instantaneous. But a velocity may be changing even though the speed is held constant. (How?)
Acceleration: rate of change of speed (speeding up or slowing down, how fast)
E.g., miles per hour per second - how many miles per hour the speed changes per second
Velocity change = acceleration X time
in "algebra-speak", Dv = at
Or: acceleration = (change of velocity)/(time interval) (a = Dv/Dt - we often use the symbol D to stand for "change of", so it reads "acceleraion equals change of velocity divided by the change of time.")
Distance = avg speed X time
= (1/2 X acceleration X time) X time
or d = 1/2 at2 (= 1/2 a x t x t )
Free Fall, Acceleration caused by gravity at sea level: g = 10 m/s2
Discuss question of forces on objects falling at same speed
Sept 7: Chapter 4 - Newton’s Second Law
For next time - read Ch 5, do the Practicing Physics pages and the HW assignment at WebAssign
Second law: force, mass and acceleration (F=ma or a = F/m)
Units: newtons= kgm m/s2
Force: applied force accelerates an object – push or pull.
Acceleration resisted by inertia (mass)
Net force – resultant of all applied forces (add vectors)
Sum of forces = zero: equilibrium (no acceleration, but can be moving –dynamic - or at rest - static)
Force yields acceleration
Free Fall – acceleration = g
g= F/m» 10 m/s2 ; Gravity - g = F/m, force of gravity on mass = weight
Mass and Weight
Kilograms and newtons (weight of 1 kilogram = 2.2 pounds)
W = mg
Proportional to weight, friction coefficient
Static and kinetic
Depends on weight, not area
Static larger than dynamic
(fluids, including air) – air resistance. Terminal speed
Free Fall and non-freefall – air resistance
Mass resists Acceleration
Length and direction
Head to tail, parallelogram methods
Sept 9: Chapter 5 – Newton’s Third Law
For next time - read Ch 6, do the Practicing Physics pages and the HW assignment at WebAssign. Next time there will be multiple choice quiz on Chapters 1-5, Bring a Zeus form!!
Forces and Interactions
Third law: action and reaction (equal and opposite forces)
Defining the system
Support forces (constraint forces, reaction forces, normal force)
Examples: Block on table, donkey and cart, rocket, road, ball and bat, ball and wall, two skaters pushing off, rifle and bullet, earth and moon
head to tail method, parallelogram method of adding two vectors
Using right triangles
***: Last day to add
Sept 14: Chapter 6 - Momentum(Quiz Ch 1-5, bring Zeus form)
For next time - read Ch 7, do the Practicing Physics pages and the HW assignment at WebAssign
Highlights, Ch 6
(= mass times velocity=mv)
= Force times time =change of momentum
=FDt = m (Dv/Dt) Dt= m Dv = D(m v)
Says, apply a force for a time, causes change in momentum)
Increasing momentum: bat, bow and arrow, golf drive, loose coupling of train cars.
Decreasing momentum gradually: catching hardball, diving into water (not concrete), falling on a mat.
Momentum transferred? – ball against wall: more if bounces or sticks?
"Conservation of momentum"
Isolated system (!) then momentum is constant (Smvinitial = Smvfinal)
Eg. Kinetic balls
Sept 16: Chapter 7 - Energy
Read Ch8, paying attention to the review questions (!) , esp 4,9,15,26,35
Do Practicing Physics :31à 36 and the webassign questions on ch 8
Work, power, energy, kinds of energy, conservation of energy
Work = force´ distance (cf. Impulse) = newton meters = joules
Power = work/time; the rate of doing work (cf. velocity) = joules/sec = watts!
So 1 kWh (what you are charged for by PGE) = 3.6 million joules. In terms of work, the joule is small. (if you are a cross-word fan, you’ll also see ergs they are even smaller = 1/10 millionth of a joule. A food calorie is 4.2 kJ (k = 1000 = 103) Also Hewitt notes that gasoline has 40 MJ/liter (M = Mega = 106)
Then: energy = ability to do work
Comes in many forms.
LAW OF CONSERVATION OF ENERGY (a big one!!)
Conservation of Energy in popular sense vs. in physics sense?
At what point in its motion is the KE of a pendulum bob the greatest? The least? Half its maximum? What is the PE at each of these points?
Conservation – Kinetic and Potential –
1. speed at bottom of incline vs. dropped from edge?
2. Efficiency – the most work one can get?
3. Work done lifting vs. holding up – work done by a statue? (difference of biological vs. physical work)
Some class questions
Can something have energy without momentum? How about kinetic energy? How about momentum without energy?
Why is there no work done when the force is perpendicular to the velocity of the object?
If a golf ball and Ping-Pong ball move at the same kinetic energy, which has the greater speed? Similarly, in a gaseous mixture of heavy (say O2) and light (say H2) molecules, which "diffuses" faster?
Does a car use more gas when its lights are turned on? Does the overall consumption of gas depend on whether the engine is turned on when you are using the lights?
A pair of identical lumps of clay collide and come to rest as a result. Is momentum conserved? Is kinetic energy conserved? Is total energy conserved?
Consider the swinging balls demo we saw. Why is that that if we release two balls, two balls pop out, and not one ball at 2X the speed?
Sept 21: Chapter 8 – Rotational Motion
Read Ch 9 (to pg 166) and Ch 10 (to pg 188 only);
Do Practicing Physics pp 37-45 and Chapter 8 HW at Webassign
rotational inertia (~ m r^2),
e.g. balance pole, using arms, etc
(how fast it rotates or goes around) (~v/r )
(=mvr, ~ rotational inertia´ rotational velocity)
torque that which causes rotation acceleration
(=r F, ~ lever arm´ force), (units: foot-lbs or newton-meters)
conservation of angular momentum
(no torques) (mvr)Initial= (mvr)Final, BUT since an isolated body can change its rotational inertia (relative to its center of inertia), it can change its rotational velocity – e.g., cats, divers, skaters, etc. (demo on turntable)
center of mass
(essentially same as center of gravity), about which free body rotates, can think of all mass centered there, extended body acts like point mass.
Example, girl on plank – 40 kg, 100 kg, 10 m
Vertical from center of gravity over base, so no torque tending to rotate-
centripetal (NOT centrifugal) force
result from inertia – bodies want to go in straight line, must be forced to turn – think of string and rock.
Sept 23: Chapter 9 - Gravity AND Chapter 10 Projectile and Satellite Motion;
Review of Mechanics End part 1
Assignment: Read Chapters 11 and 12 and do the practicing physics pages and at least 15 points of problems at WebAssign.
Note: due to the quiz on part 1, there won't be a daily quiz on the reading, BUT questions on them will be incorporated into following quizzes.
Gravitation, Newton’s Law of - Comments on importance - Impact on culture - Fundamental force, shapes universe
F=Gm1m2/r2, ~masses of each, ~ 1/r2
G = 6.7 x 10-11 N m2 /kg
Relationship to weight (F=mg), weightlessness.
Other fundamental forces, electromagnetic, nuclear strong, nuclear weak.
Inverse Square Law:
Discussion of 1/r2 physical quantities: gravitational force, electric force, light intensity, sound intensity, anything propagated from a point source (paint spray spreading).
tides, effect of moon vs. sun, gravitational field.
Full, new ->"spring tides", 90 deg "neap tides"
Gravity inside a planet, or a shell.
Drop of earth ~ 5 m in 8 km
Free fall d = 5 m after 1 sec: if v ~ 8 km/s, orbit! (Newton’s cannon)
If more -> elliptical
Potential and kinetic energy in orbit,
Does rotation of earth affect?
Launch (ve ~0.5 km/s @ equator)
Escape velocity , black holes
ve escape velocity = speed at which object leaves orbit, about 11.2 km/s for earth at surface
ve2 ~M/d (d=distance to center)
For sun (radius ~ re x 100, (re = 6.4 million m or 6 thousand km) ; Ms ~Me x 3 x 106), , ve,S =620 km/s
Speed of light : c= 3 x 108 m/s. Nothing travels faster. IF sun shrank so ve > c, NOTHING escapes, including light! black hole. True if sun shrank to 1/106 (one millionth) or about rS~3 km
earth drops 5 m in 8000 m. (or use 1 m in 1600 m, or about 1 m/mile)
Expansion of universe: a question right now, but regardless, gravity the most important force in nature on the large scale.
The essence: horizontal motion is constant, vertical motion changes as a freely falling body. Dhorizontal = vhorizontal t; Dvertical = vvertical t - 1/2 g t2
Review, Part 1:
Inertia, force, speed, velocity, acceleration, mass vs weight, friction, vectors vs scalars, energy, potential and kinetic, power . . .
inertia - mass; "lazy", accelerating, going around a corner,
force - and reaction; force due to body = weight =mg
speed - mph, dist/time velocity: net distance
acceleration - rate of change of velocity,
force - always mass times acceleration: newtons; friction force, always opposes motion, ~ mg
vectors - direction and magnitude,
energy: mechanical kinetic and potential: many other forms. joules, calories (vsvs. kilocalories), kWh.
Power: rate of using or changing energy: watts
Tides - non-uniform pull of moon (sun's pull much stronger)
momentum, angular momentum, the conservation laws (3),
units: kg, m, s, N, joules, watts,
weight mg, momentum mv, kinetic energy 1/2 mv2, gravitational potential energy mgh rotational inertia ~mr2
angular moment ~ rotational inertia X angular rate of rotation ~ mvr
centripetal acceleration: mass on string -> tension (rock seems to pull "outward" but goes in straight line when released - inertia!)
Conservation of momentum - no outside forces in direction of motion
Conservation of angular momentum - no outside twists - earth absorbs, etc. (bicycle,
Conservation of Energy (but must define the system carefully - e.g., refrigerator)
Sept 28: Chapter 11 - The Atomic Nature of Matter; AND Chapter 12 Solids(part 1 quiz at end)
Read chapters 13 AND 14 for next time, do the Practicing physics pages for both, as always.
The Atomic Nature of Matter
Greeks – speculation of a smallest (Democratis)
18th –19th century chemistry – combination of elements ->individual atoms, weights (Avogadro, Loschmidt)
Modern understanding – atom – 10^-10 m, joined together, makeup molecules. Molecules vary from 2 atoms to millions of atoms (e.g. protein molecules)
Atoms made of nucleus, electrons, all mass in nucleus.
nucleus – 10^-15m, protons and neutrons
surrounded by thin cloud of electrons (size depends on wave properties)
electrons in shells, electrons neg., protons positive, neutron (like protons) neutral.
Atomic number, atomic mass, Avogadro’s number. Shells, charges outside closed shells determine chemical properties.
Nucleus – protons and neutrons, now know p and n made up of smaller particles "quarks" -
Mass of atom ~ 1/6 x 10^-23 grams (H)
Periodic Table – shows shells – similar elements having similar outer shell.
Phases – solid liquid gas plasma
– molecule in regular, fixed arrays, bound together. Binding may be "ionic, covalent, metallic, "van der Walls"; size varies from 2 atoms to millions.
Properties of solids: molecules connected by springs, vibrate as heat up, expand.
Tension, compression, strength of arches
Strength ~area - r^2
Weight ~ volume - r^3
Wind resistance ~ area
Sept 30: Chapter 13 - Liquids; Chapter 14 - Liquids; Gases and Plasmas: End part 2
Chapter 15 for next time and start of Chapter 16 (about to page 313)
Pressure in a liquid (liquid pressure = weight density X depth)
Bouyancy (weight of displaced liquid): Archimedes' Principle
Pascal's Principle: (pressure transmitted throughout)
Surface tension, capillarity
Atmosphere, atmospheric pressure, mass of air (1 m^3 ~ 1 1/4 kilograms at sea level)
Air Pressure ~1/2 @ 5.6 km,
Weight of air ~ 10 N/cm^2 or 10^5 N/m^2 ~ 100kPa , ~ 10.3 m of water
Gas Law: pressure-volume (Boyle's law - const T)
PV = nRT which says PV= cons't for fixed temp, V~T for fixed P (eg., atmospheric)
Gases cool on expansion -
Air Speed increases, pressure decreases.
Plasma - think neon display
Review Chapters 12-14
In essence, these chapters teach us that all matter is composed of atoms held together by electrical forces. All materials exist as solids, liquids or gases given the right conditions. Solids are held most tightly; as heat is applied, the solid melts and becomes liquid, and as heat is applied further, it becomes gas. All materials can be characterized by their density (greatest for solids, least for gases) Solids can be in compression or tension. Liquids and gases can only undergo compression, and do not support tension. A important concept for both liquids and gases is pressure (force/area) and buoyancy (uplifting force equal to weight of displaced fluid.) Pressure is the same at the same height in either a liquid or a gas. Additional pressure applied is transmitted uniformly through the fluid. In Ch 15 we find both solids and liquids expand some with increase in temperature, but resist compression. However, gases change their volume greatly with changes in temperature or pressure (V ~ T/P, where T measured in kelvins). Bernoulli's principle says that a gas has reduced pressure where it moves faster.
October 5: Chapter 15 Temperature, Heat, and Expansion; Start Chapter 16 - Heat Transfer
scales: relative measure of internal kinetic energy, direction of heat flow, measure - degrees. Temperature Calibration - "fixed points", absolute zero.
Heat - another form of energy!
quantity - usually calories, Btu's, Calories. Internal amount - heat capacity - touching a hot iron, hot wood, hot Al foil, etc. Water - high heat capacity (water: 1 cal/gm-BIG) e.g. Pie Vs filling
of solids (demo), ocean levels (more on thermal expansion than change in amount of mass)
Water expands when freezes
3 primary means: Conduction, Convection, Radiation
Conduction: direct contact exchange of heat, usual method between solids
Convection: motion of molecules carrying kinetic energy, exchanging energy
Radiation: heating by photons, that is, by electromagneitc radiation; e.g., the sun.
? Why do you feel cooler when you move away from a fire, but always the same with the sun?
Example of thermos bottle - controls all three.
October 7: Finish Chapter 16- Heat Transfer; Chapter 17 - Change of Phase:
Ch 18 is for next time and that finishes part 3. There will be a Multiple Choice quiz on parts 2 & 3 in a week from today.
Change of phase:
Evaporation (condensation); melting (freezing); absorb heat (lose heat)
Associated with change in connection of molecules to neighbors; more kinetic energy makes it more difficult for molecules to "stick".
Evaporation - those molecules leaving take energy, work of "leaving", leaving less - cooling
Occurs all the time. Higher temp - air holds more water vapor, less likely to condense.
Boiling - change of phase interior of liquid. Occurs at a definite temp for given conditions (temperature, atmospheric pressure) = BP
Vapor bubbles ~ 1 atm internal, increase or decrease by pressure change. Covering a pan reduces heat needed - mostly due to reduction in loss of heat.
Cooling, refrigeration uses, air conditioning, "heat pump"
Kinetic energy added enough to disrupt rigid bonds.
Evaporation, Condensation, melting, freezing, latent heat
Evaporation (i.e., boiling) is a cooling process!! (takes away heat)
Latent heat - amount of energy to change phase, temperature remains fixed while at phase change. Water- 80 cal/gm melting; 540 cal/gm boiling
October 12: Chapter 18- Thermodynamics; End part 3
(Multiple Choice Quiz on parts 2 and 3 next time)
Sum of all energy changes = 0
Change of energy = heat in – work out
No heat gained or lost - important for engines, atmosphere - work done = loss of internal energy, cooling; work on = increase of internal energy (bicycle pump)
E.g. Cooling at higher elevations, (~ 10 C per km), Chinook winds,
Temp inversion, convection of ocean, mantle
e.g., electric power plant (steam), run at superheated steam, 700 K = Thot; 300 K == Tcold; e=400/700 ~60% (actually, most are less, have e~35-45%)
e.g. automobile e (using gasoline) ~ 26% to mechanical (electric cars, ~90%(?), but then times the 40% at the power plant - still, far less pollution))
Heat engine (heat to work: cyclic) - Heat flow always hot to cold, for engine, always have heat rejected, ideal efficiency e=(Thot-Tcold)/Thot (T in kelvins)- the best one can do.
a measure of "disorder" - 2nd law says universe tending towards greater entropy.
Review Chapters 12-14
In essence, these chapters teach us that all matter is composed of atoms held together by electrical forces. All materials exist as solids, liquids or gases given the right conditions. Solids are held most tightly; as heat is applied, the solid melts and becomes liquid, and as heat is applied further, it becomes gas. All materials can be characterized by their density (greatest for solids, least for gases) Solids can be in compression or tension. Liquids and gases can only undergo compression, and do not support tension. A important concept for both liquids and gases is pressure (force/area) and buoyancy (uplifting force equal to weight of displaced fluid.) Pressure is the same at the same height in either a liquid or a gas. Additional pressure applied is transmitted uniformly through the fluid. In Ch 15 we find both solids and liquids expand some with increase in temperature, but resist compression. However, gases change their volume greatly with changes in temperature or pressure (V ~ T/P, where T measured in kelvins). Bernoulli's principle says that a gas has reduced pressure perpendicular to the direction of increased velocity of flow.
Review Ch 16-18
The subject of heat and thermodynamics studies another from of energy. Central to these studies are the First Law, the Second Law, the concept of entropy, and the relationship of heat and work (and efficiency).
October 14: Chapter 19 - Vibrations and Waves
Quiz, parts 2 &3 today
For next time, read Chapter 20.Sound and Chapter 21, Musical Sounds. (There are no Practicing Physics pages for Chapter 21
Simple harmonic motion (SHM)
"sine wavelike motion" wavelength, frequency, period
frequency (cycles/sec)= number of cycles (or "shakes" or vibrations) per second
unit: call cycles per second = hertz; e.g., ac current = 60 cycles per second = 60 hertz. KQED at 88.5 MHz (megahertz) = 88.5 million cycles per second)
period = T = time for one shake or cycle = inverse of frequency (= 1/f : seconds per cycle)
amplitude – size of vibration
restoring force, causes "oscillations" e.g., pendulum, spring and weight.
Waves - Like SHM in motion
speed (or velocity) of wave = distance / time; wavelength - distance wave goes in one period; if wave travels one wavelength, v =l /T = l f, the basic equation for waves v = l f, use l (greek "lambda")
Vibrations of waves: Transverse, Longitudinal
Change of speed as cross boundary, e.g. from air into glass
Waves recombine with self - e.g. max and minima from two speakers, or combining with reflection
Constructive or destructive
Standing waves - interference - nodes (where cancel) and antinodes
Waves "bend" some around corners.
Bow wave, shock waves
Speed of waves:
Sound, v ~ 340 m/s ~
Light (more later) v = 3.00 X 108 m/s
Allwaves (sound, light, water, etc.) refract, diffract, interfere
October 19: Chapter 20 - Sound & Chapter 21 - Musical Sounds: end part 4
Read Chapter 22 and the review questions. As always, do the Chapter- associated Practicing Physics pp75-76, (don't forget to go to Webassign for the HW exercises and problems.)
Compression waves, 330 m/s
Sympathetic vibrations, beats
Frequency, "quality", harmonics
energy per unit area, bels, decibels, logarithmic scale (powers of 10) Painful - 1 W/m2 = 120 dB; just audible 10-12 W/m2 = 0 dB, conversation ~ 60 dB, loud traffic ~70-80dB.
Loudness subjective, not the same as intensity
October 21: Finish Sound, if needed; Chapter 22 - Electrostatics
Assignment Read Chapter 23, Electric Current. Do Practicing Physics pp77-79 (don't forget to go to WebAssign for the HW exercises and problems.) (this is a complicated and important chapter and set of exercises in the practicing physics pages: we'll finish these next time)
Electrical Forces, Electrical Charge
Atoms, electrons, coulombs, conservation of charge
Coulomb's Law - ~q1q2/r2
Cf. Newtons Law of Gravitation
Cf. Heat transfer
Charging, transfer of charge
Charging by induction
Differences between conductors, insulators
The Electric Field (and differences with gravitational field)
"alteration of space"
From (+) to (–)
Conductors shield, insulators change
The Electric Potential
Potential energy per unit charge - "voltage
joule/coulomb = volts
field - measured by volts/meter
Capacitor - stores (+), (-) charge at potential difference
volts X coulombs = joules
battery - converts chemical energy into separated charge at potential difference; again, coulombs X volts = joules
October 26: Chapter 23 - Electric Current
Do Practicing Physics pp80-84 (Chapter 23); Read Chap 24(don't forget to go to WebAssign for the HW exercises and problems.)
Charge flow: Coulombs/sec = amperes "conventional"à + to –
Electrical pressureà electric potential: volts
Voltage sources: batteries, generators, power supplies,
Closed circuit, Speed of electron flow, of electrons
Ohm’s Law: Current ~ Voltage/Resistance: I = V/R (amps = volts/ ohms)
Comments on electric shock – heart electrical pattern, destruction of nervous system Body resistance ~ 102 – 106W
Potential difference: biological, shock, language
Dirct vs. alternating current (DC, AC),
Alternating voltage : Household 120 V avg.
Voltage times current; watts = amps X volts
Series, parallel circuits
House circuits often 15 amps (1500 watts/110 volts = 14 amps)
October 28: Chapter 24 -- Electric Current(concldd) Magnetism
Assignment Read Chap 25 Do Practicing Physics pp 85-88(don't forget to go to WebAssign for the HW exercises and problems.)
N, S poles
All magnets have both
N = "north-seeking" points to North, etc.
Opposites attract, like repel
Source – electrons in "orbits", electric currents
Forces on moving charges
Probably due to currents in core.
Shields us from high energy particles emitted by sun
(picture of recent solar flare see sohowww.nascom.nasa.gov/hotshots/X17)
Selection of great (!) aurora pictures as a result of above, see
November 2: Chapter 25 - Electromagnetic Induction,
Assignment Read Chap 26 Do Practicing Physics pp 89-90, (don't forget to go to WebAssign for the HW exercises and problems.)MC Quiz next Tuesday, parts 4-5, Ch 26
Field lines (or flux) cutting wire - induces current
Demo: "induction coil"
Rotate coil in field = generator (produces voltage)
Max voltage - right angles between field lines and movement of wire.
Transformers (coupled flux)
Couple changes of flux (recall flux = field through an area)
if ac in one, changing flux in other, produces voltage.
Voltage/# of turns)A = Voltage/# of turns)B
NA / NB = VA / VB
But power (VI) remains constant.(energy conservation)
Power transmission - Hi V , Lo I
VI - constant, so use high V, low I, so have less heating loss in wires (I2R). Usually 10.4 kV to transformer by house, hundreds of thousands of V for cross country transmission, 220 V into house
November 4: Chapter 26 - Properties of Light
MC Quiz next Tuesday, Parts 4 & 5 and Chap 26
Assignment: Read Chapter 27, do Practicing Physics pp. 91-92 (don't forget to go to WebAssign for the HW exercises and problems.)
A great (and fun) web site for this chapter (see extra credit below, also)
Do the Tutorial on Color at Physicsplace, turn in a description of what you did and how it worked out.(this is a very good one)
Or go to
Changing magnetic field produces changing electric, vice versa -
Velocity = c = 3 X 108 m/s = velocity of light
In 1 cycle at 1 GHz (1x 109 ); period = 10-9 s, d = 3 x 108 m/s x 10-9 s = 0.3 m, size of a computer; or, distance light travels in a nanosecond = 30 cm.; in a microsecond = 300 m, etc.
EM spectrum -
radio (meter to 100's of meters), microwaves (fractions of m down to millimeters), infrared (millimeters to microns (10-6 m)), visible light (10-6 to 10-7 m), ultraviolet (10-7 to 10-9 m), x-rays (10-9 m to 10-11 m ), "gamma rays" (10-11 m to ??)
Transparent vs. opaque materials:
ties to vibrations of electrons in atoms.
Shadows, sharp and diffuse,
Shadow from sun: Umbra, penumbra
Metallic reflection - vibrations of electrons.
Optical illusions: go to (!!!)http://www.eyetricks.com or
November 9: Chapter 27 - Color
(MC Quiz today) Assignment:Read Ch 28, Reflection and Refraction. Do Practicing Physics pp. 93 --104 (this is a long but very informative set), (don't forget to go to WebAssign for the HW exercises and problems.)
Selective reflection and transmission
Mixing colored light and colored pigments
Additive and Subtractive, Complementary colors
Some color phenomena
November 11: Chapter 28 - Reflection and Refraction
Assignment: (for do for next time, but turn in at next quiz date
Read Chapter 29, Light Waves. Do Practicing Physics pp 105-108, (don't forget to go to WebAssign for the HW exercises and problems.)
Highlights (the link to the simulations relevant to today is
equal angles, virtual image, plane, concave and convex mirrors, reflection from diffuse and polished surfaces.
Light bending as moves obliquely from different speed media.
Different speeds for different wavelengths in some media. Cause of separation of colors by a prism and by rainbows
Total internal reflection
Since light from lower speed media bends away from perpendicular, at some angle there's no room (fig 27.36).
Prisms in binoculars
Optical fiber "light pipes."
November 16: Chapter 29 - Light Waves
Read Chapter 30 and start 31. Do Practicing Physics pg109 (Due with pg. 110 for Ch 33)(don't forget to go to WebAssign for the HW exercises and problems.)
and go tohttp://www.colorado.edu/physics/2000/quantumzone/, navigate around the site, and for extra credit, write a page on the interactive demos you looked at (including the spectral signatures interactive demo).
Huygen's principle -
that any element of a wave front can be viewed as generating new spherical waves that add to give new wave fronts. Allows explanation of diffraction, interference.
Waves bend around a barrier (Fig 28.7), spread when going through a slit. The longer the wavelength the greater angle of bending (explains why one hears sound waves behind a wall between you and speaker, e.g.)
Constructive and destructive addition of waves, produces "interference fringes."
When white light passes through a thin film (such as reflecting from water with an oil film on top - the thin film, see colors as a result of some waves adding, others canceling.
Direction of light vibrations, absorption of one, polarization of skylight, light by strained materials.
November 18: Chapter 30 - Light Emission, (bring a trash CD to use as a diffraction grating) Chapter 31 - Light Quanta (start)
Finish Ch 31, Read Ch32. Do Practicing Physics pg110
Atoms: excitation, emission of radiation.
Emission spectra, absorption spectra, Fluorescence, incandescence, phosphorescence, lasers
Chapter 31 - Light Quanta
Finish Ch 32. Practicing Physics pg 111-112; First Reading Ch 33, do Practicing Physics p 111-112, (don't forget to go to WebAssign for the HW exercises and problems.)
Highlights, Ch 31
Birth of the Quantum theory
Quantization and Planck's Constant
Photoelectric Effect, the photon
Wave Particle duality
Double Slit Experiment
Waves as Particles Wave-
The double slit experiment
November 23: Chapter 32, The Atom and the Quantum
Ch 32 Atomic Spectra, Bohr model, relative sizes, Explanation of quantized levels, Quantum mechanics, particles as waves, Complementarity
Electron Waves and Quantum Mechanics
Explanation of quantized levels, particles as waves standing waves in atom.
Probability description of electron, etc.
November 25-28: Thanksgiving Holiday
November 30: Finish Chapter 32, : Chap 33 - The atomic nucleus, radioactivity
Read Ch 34, do Practicing Physics pg 113(don't forget to go to WebAssign for the HW exercises and problems.)
x-rays, alpha, beta, gamma rays
Effects of Radioactivity
Dosage and exposure
Discovery of the Atomic Nucleus
The Nucleus (Isotopes, nuclear stability, half-lifes, natural transmutation, artificial transmutation, carbon dating)
Atomic number, atomic mass number
Half-lifes, carbon dating
p's and n's, short range force and coulomb repulsion
combinations, stability and decay Transmutation
natural transmutation, artificial transmutation,.
Leptons (e,v) quarks (u,d): lowest energy combination of quarks (p,n)
kinds of changes of nucleus, driving force and mass-energy equivalence E=mc2
Basics of a fission reactor
December 2: Chapter 34, Nuclear Fusion and Fission
Assignment:Review your work and quizzes for questions for next time class review
There will be a Quiz next time covering Ch's 27-34
Copy, fill in, and turn in copies (keep a copy for study) the sample quizzes for parts 1-7
These will not be graded, but doing them will give extra credit pints towards your quiz grade - to get credit,you need to have done all the quizzes for parts 1-7.
We will go over the questions briefly in response to your questions.
p's and n's, short range force and coulomb repulsion
combinations, stability and decay
driving force and mass-energy equivalence E=mc2
The basic curve of nuclear stability
Nature ALWAYS seeks lowest energy state!
Nuclear Reactions, cont.' - Fission and Fusion
Nuclear forces - contact attraction, charge repulsion
92235U and 94239Pu; U(238)
Basics of a fission reactor
Nucleons, quarks (u,dà p,n); Leptons fa(electrons, neutrinos)
December 7: Modern Physics wrap-up, Quiz Ch 27-34: Bring Zeus form!
Review, final preparation
Review your work and quizzes for questions for class review
DON'T FORGET TO BRING A ZEUS FORM TO THE FINAL!
:wrap-up review(bring ZEUS form)
Go over last quiz, answer questions, anything left over to do
December 9: course wrap-up (Dec 10: Last day of instruction for semester)
Dec 14: Final Exam: 1045 – 1315, Room Sci 201:
Don't forget to bring a full page Zeus form and a pencil.