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PHYS 1444 – Section 001 Lecture #1

PHYS 1444 – Section 001 Lecture #1. Tuesday June 5, 2012 Dr. Andrew Brandt, with Ian Howley and Ryan Hall. Introduction (longish) and Syllabus Chapter 21 -Static Electricity and Charge Conservation -Charges in Atom, Insulators and Conductors & Induced Charge -Coulomb’s Law.

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PHYS 1444 – Section 001 Lecture #1

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  1. PHYS 1444 – Section 001 Lecture #1 Tuesday June 5, 2012 Dr. Andrew Brandt, with Ian Howley and Ryan Hall • Introduction (longish) and Syllabus • Chapter 21 • -Static Electricity and Charge Conservation • -Charges in Atom, Insulators and Conductors & • Induced Charge • -Coulomb’s Law Please turn off electrical devices in class Thanks to Dr. Yu for bringing this class into 21st Century! PHYS 1444-001, Dr. Andrew Brandt

  2. My Background+Research B.S. Physics and Economics College of William&Mary 1985 PH.D. UCLA/CERN High Energy Physics 1992 (UA8 Experiment-discovered hard diffraction) 1992-1999 Post-doc and Lab Scientist at Fermi National Accelerator Laboratory -1997 Presidential Award for contributions to diffraction -Proposed and built (with collaborators from Brazil) DØ Forward Proton Detector -Physics Convenor -Trigger Meister 1999 Joined UTA as an Assistant Professor 2004 promoted to Associate Professor 2010 promoted to Full Professor - Funding from NSF, DOE, and Texas approaching 10M$ as PI or Co-PI PHYS 1444-001, Dr. Andrew Brandt

  3. My Main Research Interests • High Energy Physics (aka Particle Physics) • Physics with Forward Proton Detectors (detect protons scattered at small angles) • Fast timing detectors (How fast? Really really fast!) http://www.youtube.com/watch?v=By1JQFxfLMM&feature=related • Triggering (selecting the events to write to tape): at ATLAS must choose most interesting 300 out of up to 40,000,000 events/sec • Higgs Discovery • Weapons of Mass Destruction (detection of) PHYS 1444-001, Dr. Andrew Brandt

  4. Primary Web Page http://www-hep.uta.edu/~brandta/teaching/su2012/teaching.html PHYS 1444-001, Dr. Andrew Brandt

  5. Grading • Exams: 3*20% • Two midterms and one final • Comprehensive final (some extra credit for incentive) • Exams will be curved if necessary • No makeup tests • Homework: 20% • Lab score: 20% PHYS 1444-001, Dr. Andrew Brandt

  6. Homework Solving homework problems is the best (only?) way to comprehend class material An electronic homework system has been setup Homework: will be done with Mastering Physics (can buy it with or without text book (costs more but worth it!) http://www.masteringphysics.com/ Course ID: MPBRANDT1444SU12 First “assignment” due Saturday!!! It is meant to teach you how to use mastering physics 2Nd (first real assignment) due next Tuesday—don’t blame me it wasn’t my idea to take a summer class! How many of you are taking this class since it is required? PHYS 1444-001, Dr. Andrew Brandt

  7. Mastering Physics Grades For grading purposes, some numeric answers to questions need to be exact. For example, the answer to the question "How many days are in a week?" must be 7. The typical grading tolerance for most numeric answers in Mastering assignment questions is between 2%-3%. For example, if the grading tolerance is 2% and the correct answer is 1043, both 1042 or 1045 are also graded as correct. When an answer is within tolerance, but doesn't match the correct answer: The officially correct answer displays in a purple box (provided that Show Whether Answer is Correct is set to Always). Students should use this answer if subsequent parts of an assignment item require calculations based on this answer. Students should use at least three digits or significant figures in answers, unless otherwise specified or unless the exact answer can be expressed using fewer than three significant figures. If higher precision is required, or lower precision is allowed, this is specified in the question or its instructions. When students must do multiple calculations to get an answer they should use more significant figures than required during each calculation and round off at the end You are allowed 6 attempts at a non multiple choice question (with each attempt you lose some points). If you get a wrong answer: reread problem, could you have made a sign error or a unit error or a round-off error? PHYS 1444-04 Dr. Andrew Brandt

  8. Attendance and Class Style • Attendance: • is STRONGLY encouraged, but I will not take attendence • Class style: • Lectures will be primarily on electronic media • The lecture notes will be posted AFTER each class • Will be mixed with traditional methods • Active participation through questions and discussion are encouraged (chances are someone else has the same question) PHYS 1444-001, Dr. Andrew Brandt

  9. Matter Molecule Atom Nucleus Baryon Quark (Hadron) u 10-14m cm 10-9m 10-10m 10-15m <10-19m top, bottom, charm, strange, up, down protons, neutrons, mesons, etc. p,W,L... Atomic Physics Nuclear Physics Electron (Lepton) <10-18m High Energy Physics Structure of Matter Nano-Science/Chemistry High energy means small distances PHYS 1444-001, Dr. Andrew Brandt

  10. Periodic Table Helium Neon u d u u d d All atoms are made of protons, neutrons and electrons Electron Neutron Proton Gluons hold quarks together Photons hold atoms together PHYS 1444-001, Dr. Andrew Brandt

  11. What is High Energy Physics? • Study of Matter/Forces at the most fundamental level. • Great progress! The “STANDARD MODEL” • BUT… many mysteries • => Why so many quarks/leptons?? • => Why four forces?? Unification? • => Where does mass come from?? • => Are there higher symmetries?? • What is the “dark matter”?? • Will the LHC create a black hole that destroys the Earth? • But if it did, it might look like: • http://www.youtube.com/watch?v=BXzugu39pKM NO! See: http://public.web.cern.ch/Public/en/LHC/Safety-en.html

  12. Role of Particle Accelerators • Smash particles together • Act as microscopes and time machines • The higher the energy, the smaller object to be seen • Particles that only existed at a time just after the Big Bang can be made • Two method of accelerator based experiments: • Collider Experiments: protons, anti-protons, electrons, muons? • Fixed Target Experiments: Particles on a target • Type of accelerator depends on research goals PHYS 1444-001, Dr. Andrew Brandt

  13. Chicago  CDF p DØ Tevatron p Fermilab Tevatron and CERN LHC • Highest Energy (proton-proton) collider since fall 2009 • Ecm=14 TeV (=44x10-7J/p 1000M Joules on 10-4m2) • Equivalent to the K.E. of a 20 ton truck at a speed 711 mi/hr • Currently 8TeV collisions • \ Highest Energy proton-anti-proton collider • Ecm=1.96 TeV (=6.3x10-7J/p 13M Joules on 10-4m2) • Equivalent to the K.E. of a 20 ton truck at a speed 81 mi/hr 1500 physicists 130 institutions 30 countries 5000 physicists 250 institutions 60 countries CERN: http://www.cern.ch/ ; ATLAS: http://atlas.web.cern.ch/ Fermilab: http://www.fnal.gov/ ; DØ: http://www-d0.fnal.gov/

  14. DØ Detector 30’ 30’ 50’ ATLAS Detector • Weighs 10,000 tons • As tall as a 10 story building • Can inspect 1,000,000,000 collisions/second • Recors 200 -300 collisions/second • Records 300 Mega-bytes/second • Will record 2.0x1015 (2,000,000,000,000,000) bytes each year (2 PetaByte). • Weighs 5000 tons • As tall as a 5 story building • Can inspect 3,000,000 collisions/second • Record 100 collisions/second • Records 10 Mega-bytes/second • Recording 0.5x1015 (500,000,000,000,000) bytes per year (0.5 PetaBytes).

  15. Tevatron: World’s 2ndHighest Energy Collider Fermilab DØ High-tech fan One of the DØ Forward Proton Detectors built at UTA and installed in the Tevatron tunnel PHYS 1444-001, Dr. Andrew Brandt

  16. Elastic Scattering Cross Section (FPD) PHYS 1444-001, Dr. Andrew Brandt

  17. ATLAS Forward Protons: A (10) Picosecond Window on the Higgs Boson A picosecond is a trillionth of a second. This door opens ~once a second, if it opened every 10 picoseconds it would open a hundred billion times in one second (100,000,000) Light can travel 7 times around the earth in one second but can only travel 3 mm in 10 psec Yes, I know it’s a door, not a window! PHYS 1444-001, Dr. Andrew Brandt

  18. Forward Proton Fast Timing WHY? Pileup Background Rejection Ex: Two protons from one interaction and two b-jets from another How? Use time difference between protons to measure z-vertex and compare with tracking z-vertex measured with silicon detector How Fast? 10 picoseconds is design goal (light travels 3mm in 10 psec!) gives large factor of background rejection PHYS 1444-001, Dr. Andrew Brandt

  19. beam splitter Picosecond Test Facility featuring initial Undergraduate Laser Gang (UGLG) Undergraduate Laser Youths? (UGLY) You too can be UGLY (but only if you are a physics major) [Don’t quote me on that!] LeCroy Wavemaster 6 GHz Oscilloscope mirror filter MCP-PMT lenses laser Hamamatsu PLP-10 Laser Power Supply Laser Box PHYS 1444-001, Dr. Andrew Brandt

  20. Why Do Physics? Exp.{ Theory { • To understand nature through experimental observations and measurements (Research) • Establish limited number of fundamental laws, usually with mathematical expressions • Explain and predict nature • Theory and Experiment work hand-in-hand • Theory generally works under restricted conditions • Discrepancies between experimental measurements and theory are good for improvement of theory • Modern society is based on technology derived from detailed understanding of physics PHYS 1444-001, Dr. Andrew Brandt

  21. Why Do Physics Part Deux http://www.aps.org/publications/apsnews/200911/physicsmajors.cfm 2008/2009 Graduates 1.7% unemployment While engineering starting salaries are typically higher than physicists, mid-career salaries are virtually identical 101k$ for engineering 99k$ for physics PHYS 1444-001, Dr. Andrew Brandt

  22. What Do Physicists Do? PHYS 1444-001, Dr. Andrew Brandt

  23. Brief History of Physics • AD 18th century: • Newton’s Classical Mechanics: A theory of mechanics based on observations and measurements • AD 19th Century: • Electricity, Magnetism, and Thermodynamics • Late AD 19th and early 20th century (Modern Physics Era) • Discovery of electron • Einstein’s theory of relativity: Generalized theory of space, time, and energy (mechanics) • Quantum Mechanics: Theory of atomic phenomena (small distance scales) • Physics has come very far, very fast, and is still progressing, yet we’ve got a long way to go • Particle physics and astrophysics final frontier? PHYS 1444-001, Dr. Andrew Brandt

  24. Need for Standards and Units • Three basic quantities for physical measurements • Length, Mass, and Time • Need a language so that people can understand each other (How far is it to Chicago? 1000) • Consistency is crucial for physical measurements • The same quantity measured by one person must be comprehensible and reproducible by others • A system of unit called SI (SystemInternational) established in 1960 • Length in meters (m) • Mass in kilo-grams (kg) • Time in seconds (s) PHYS 1444-001, Dr. Andrew Brandt

  25. SI Base Quantities and Units

  26. deci (d): 10-1 centi (c): 10-2 milli (m): 10-3 micro (m): 10-6 nano (n): 10-9 pico (p): 10-12 femto (f): 10-15 atto (a): 10-18 Prefixes and their meanings • deca (da): 101 • hecto (h): 102 • kilo (k): 103 • mega (M): 106 • giga (G): 109 • tera (T): 1012 • peta (P): 1015 • exa (E): 1018 Impress your friends!

  27. Examples 1.3 and 1.4 for Unit Conversions • Ex 1.3: A silicon chip has an area of 1.25in2. Express this in cm2. • Ex 1.4: Where the posted speed limit is 65 miles per hour (mi/h or mph), what is this speed (a) in meters per second (m/s) and (b) kilometers per hour (km/h)? (a) Oops, what about sig. figs.? (b) About how fast did Usain run in MPH?

  28. { Systematic Uncertainties • Physical measurements have limited precision, no matter how good they are, due to: Number of measurements Quality of instruments (meter stick vs micrometer) Experience of the person doing measurements Etc. In many cases, uncertainties are more important and difficult to estimate than the central (or mean) values Statistical { PHYS 1444-001, Dr. Andrew Brandt

  29. Significant Figures • Significant figures denote the precision of the measured values • Significant figures: non-zero numbers or zeros that are not place-holders • 34 has two significant digits; 34.2 has 3; 0.001 has one because the 0’s before 1 are place holders, 34.100 has 5, because the 0’s after 1 indicates that the numbers in these digits are indeed 0’s. • When there are many 0’s, use scientific notation: • 31400000=3.14x107 • 0.00012=1.2x10-4 PHYS 1444-001, Dr. Andrew Brandt

  30. Significant Figures • Operational rules: • Addition or subtraction: Keep the smallest number ofdecimal places in the result, independent of the number of significant digits: 34.001+120.1=154.1 • Multiplication or Division: Keep the number of significant figures of the operand with the least S.F. in the result: 34.001x120.1 = 4083, because the smallest number of significant figures is 4. • For homework may need to get this right! PHYS 1444-001, Dr. Andrew Brandt

  31. Static Electricity; Electric Charge and Its Conservation • Electricity is from Greek word elecktron=amber, a petrified tree resin that attracts matter if rubbed • Static Electricity: an amber effect • An object becomes charged or “posses a net electric charge” due to rubbing • Example: Rub feet on carpet and zap your little sister • Two types of electric charge • Like charges repel while unlike charges attract • Benjamin Franklin referred to the charge on a glass rod as the positive, arbitrarily. Thus the charge that attracts a glass rod is negative.  This convention is still used. PHYS 1444-001, Dr. Andrew Brandt

  32. Static Electricity; Electric Charge and Its Conservation • Franklin argued that when a certain amount of charge is produced on one body in a process, an equal amount of opposite type of charge is produced on another body. • The positive and negative are treated algebraically so that during any process the net change in the amount of produced charge is 0. • When you comb your hair with a plastic comb, the comb acquires a negative charge and the hair an equal amount of positive charge. • This is the law of conservation of electric charge. • The net amount of electric charge produced in any process is ZERO!! • If one object or one region of space acquires a positive charge, then an equal amount of negative charge will be found in neighboring areas or objects. • No violations have ever been observed. • This conservation law is as firmly established as that of energy or momentum. PHYS 1444-001, Dr. Andrew Brandt

  33. Electric Charge in the Atom • It has been understood through the past century that an atom consists of • A positively charged heavy core  What is the name? • This core is the nucleus and consists of neutrons and protons. • Many negatively charged light particles surround the core  What is the name of these light particles? • These are called electrons • How many of these? • So what is the net electrical charge of an atom? • Zero!!! Electrically neutral!!! • Can you explain what happens when a comb is rubbed on a towel? • Electrons from towel get transferred to the comb, making the comb negatively charged while leaving positive ions on the towel. • These charges eventually get neutralized primarily by water molecules in the air. As many as the number of protons!! PHYS 1444-001, Dr. Andrew Brandt

  34. Insulators and Conductors • Picturetwo metal balls, one of which is charged • What will happen if they are connected by • A metallic object? • Charge is transferred, until the charge is evenly distributed • These objects are called conductors of electricity. • A wooden object? • No charge is transferred • These objects are called insulators. • Metals are generally good conductors whereas most other materials are insulators. • A third kind of materials called semi-conductors, like silicon or germanium  conduct only in certain conditions • Atomically, conductors have loosely bound electrons while insulators have tightly bound electrons! PHYS 1444-001, Dr. Andrew Brandt

  35. Induced Charge • When a positively charged metal object is brought close to an uncharged metal object • If the objects touch each other, the free electrons in the neutral ones are attracted to the positively charged object and some will pass over to it, leaving the neutral object positively charged. • If the objects get close, the free electrons in the neutral object still move within the metal toward the charged object leaving the opposite end of the object positively charged. • The charges have been “induced” in the opposite ends of the object. PHYS 1444-001, Dr. Andrew Brandt

  36. ground Induced Charge • We can induce a net charge on a metal object by connecting a wire to ground. • The object is “grounded” or “earthed”. • Since it is so large and conducts, the Earth can give or accept charge. • The Earth acts as a reservoir for charge. • If the negative charge is brought close to a neutral metal rod • Positive charges in the neutral rod will be attracted by the negatively charged metal. • The negative charges in the neutral metal will gather on the opposite side, transferring through the wire to the Earth. • If the wire is cut, the metal bar has net positive charge. • An electroscope is a device that can be used for measuring charge – How? PHYS 1444-04 Dr. Andrew Brandt

  37. Coulomb’s Law • Charges exert force on each other. What factors affect the magnitude of this force? • Charles Coulomb figured this out in 1780’s. • Coulomb found that the electrical force is • Proportional to the product of the two charges • If one of the charges is doubled, the force doubles. • If both of the charges are doubled, the force quadruples. • Inversely proportional to the square of the distances between them. • Electric charge is a fundamental property of matter, just like mass. • How would you put this into a formula? PHYS 1444-04 Dr. Andrew Brandt

  38. Coulomb’s Law – The Formula Formula • Is Coulomb force a scalar quantity or a vector quantity? Unit? • A vector quantity. Newtons • Direction of electric (Coulomb) force is always along the line joining the two objects. • If two charges have the same sign: forces are directed away from each other. • If two charges are of opposite sign: forces are directed toward each other. • Coulomb’s Law is accurate to 1 part in 1016. • Unit of charge is called Coulomb, C, in SI. • The value of the proportionality constant, k, in SI units is • Thus, if two 1C charges were placed 1m apart the force would be 9x109N. PHYS 1444-04 Dr. Andrew Brandt

  39. and Gravitational Force Electric Force Extremely Similar • Does the electric force look similar to another force? What is it? • Gravitational Force • What are the sources of the forces? • Electric Force: Charge, fundamental property of matter • Gravitational Force: Mass, fundamental property of matter • What else is similar? • Inversely proportional to the square of the distance between the sources of the force  What is this kind law called? • Inverse Square Law • What is different? • Gravitational force is always attractive. • Electric force depends on the sign of the two charges. • Magnitude PHYS 1444-04 Dr. Andrew Brandt

  40. The Elementary Charge and Permittivity • Elementary charge, the smallest charge, is that of an electron: • Since electron is a negatively charged particle, its charge is –e. • Object cannot gain or lose fraction of an electron. • Electric charge is quantized. • It always occurs in integer multiples of e. • The proportionality constant k is often written in terms of another constant, e0, the permittivity of free space. They are related and . • Thus the electric force can be written: • Note that this force is for “point” charges at rest. PHYS 1444-04 Dr. Andrew Brandt

  41. Example 21 – 1 • Electric force on electron due to proton. Determine the magnitude of the electric force on the electron in a hydrogen atom exerted by the single proton (Q2=+e) that is its nucleus. Assume the electron “orbits” the proton at its average distance of r = 0.53 x10-10 m. (0.5 Angstrom) Using Coulomb’s law Each charge is and So the magnitude of the force is Which direction? Towards each other… PHYS 1444-04 Dr. Andrew Brandt

  42. Example 21 – 2 • Which charge exerts greater force? Two positive point charges, Q1=50mC and Q2=1mC, are separated by a distance L. Which is larger in magnitude, the force that Q1 exerts on Q2 or the force that Q2 exerts on Q1? What is the force that Q1 exerts on Q2? What is the force that Q2 exerts on Q1? Therefore the magnitudes of the two forces are identical! Is there any difference? The direction. What is the direction? Opposite to each other! What is this law? Newton’s third law, the law of action and reaction PHYS 1444-04 Dr. Andrew Brandt

  43. Solving Problems • Read and re-read problems carefully • Draw a diagram using arrows to represent vectors • Choose a convenient coordinate system • Note the known and unknown quantities • Write down the relevant relationships • Do an approximate calculation • Solve, substituting numbers only at the end • Keep track of units • Consider if answer is reasonable PHYS 1444-04 Dr. Andrew Brandt

  44. Vector Problems • Calculate magnitude of vectors • Split vectors into x and y components and add these separately, using diagram to help determine sign • Calculate magnitude of resultant |F|=(Fx2+Fy2) • Use = tan-1(Fy/Fx) to get angle Example on board PHYS 1444-04 Dr. Andrew Brandt

  45. Announcements • Read Ch. 21 before next class • Enroll in Mastering Physics and do first “welcome” assignment • Read Book, Do HW, Go to Lab, Learn Physics • Good grade will follow PHYS 1444-04 Dr. Andrew Brandt

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