Syllabus Questions about grades grade checks absences etc

Syllabus Questions about grades, grade checks, absences, etc… please see Prof. Pyrak-Nolte

PHYS 241 Electricity & Optics • Physics Department Home page: http: //www. physics. purdue. edu/ • Course Home page: http: //www. physics. purdue. edu/phys 241/ • CHIP Home page: http: //chip. physics. purdue. edu/public/241/spring 2013/ • Piazzaz: https: //piazza. com/purdue/spring 2013/phys 241/home • • • Room 144 - Undergraduate office Room 11 - Help center Room 290 - Physics Library

Syllabus *Register your I-clicker on CHIP. *Always bring your I-clicker to class. *5% of your scores is based on lecture quizzes. CHIP: http: //chip. physics. purdue. edu/public/241/spring 2013/

Calendar *Read the assigned Chapter sections prior to attending class. *Note Exam Dates *Homework is due on Mondays at 11: 59 PM. Home work is done through CHIP Home page: http: //chip. physics. purdue. edu/public/241/spring 2013/

Syllabus

Online Forum We will use Piazza for class discussions to assist you in getting help fast and efficiently from your classmates and the teaching assistants. Rather than emailing questions to the teaching staff, you are encouraged to post your questions on Piazzaz: You can sign up for a Piazza account and enroll in our class page at: https: //piazza. com/purdue/spring 2013/phys 241/home

CLICKER LOG IN (1 point)

An Old (and Fundamental!) Question: What is the Structure of Matter in the Universe?

Size Scales in the Universe Ancient Man ~1 m Scale ~ 1026 m Wood Gravitation Iron Universe Basics Constituents Leptons Quarks Scale ~ 10 -10 m Electromagnetism Nuclei ~ 10 -15 m Strong Nuclear Force Atoms Gluons

Concept of Charge -- Charging by rubbing

friction cause electrons to move from one object to another.

DEMO #5 A 01 STATIC ELECTRICITY

CHARGING BY INDUCTION polarization by induction grounding

DEMO # 5 A-06 BRAUN, GOLD LEAF, 2 x 4 ELECTROSCOPES

QUANTIZATION OF CHARGE • Fundamental unit: elementary charge e • An electron carries a charge of –e ; a proton carries a charge of +e It is typically the electrons that move between objects. • Coulomb (C): one coulomb is the amount of charge that is transferred through the cross section of a wire in 1 second when there is a current of 1 ampere in the wire.

CONDUCTORS AND INSULATORS • Conductors: material in which electric charges can move around “freely” Cu 1029 / m 3 – Metals, tap water, human body, … • Insulators: material in which electric charges are “frozen” in place – Air, glass, plastic, … • Semi-conductor: material in which electric charges can move around but not as freely as in conductors – Silicon, germanium, … Ge 1019 / m 3

CONSERVATION OF CHARGE The net electric charge is conserved in any physical process. But … • Charge can be transferred from one object to another. • Individual charges can also, in fact, be “destroyed” or “created”, but not net charges ( annihilation) ( pair production)

COULOMB’S LAW • Charges with the same sign repel each other, and charges with opposite signs attract each other. • The electrostatic force between two particles is proportional to the amount of electric charge that each possesses and is inversely proportional to the distance between the two squared. 1, 2 by 1 on 2 q 1 q 2 r • Coulomb constant: where e 0 is called the permittivity constant.

How strong are Coulomb forces? • Electron and proton in a hydrogen atom • Compare electric and gravitational forces electron and proton me = 9. 11 x 10 -31 kg, mp =1. 67 x 10 -27 kg

Principle of Superposition q 1 F 13 • Add by components or F 12 q 3 F 1 • Magnitude and direction separately by using trigonometry

Physics 241 – 10: 30 Quiz (1 point) – January 7, 2013 Two point charges are separated by distance d as shown. Where can you put a third charge of 1 C so that there is no net electric force acting on it? (Take Q > 0. ) a) to the right of charge Q to the left of charge 2 Q b) c) between the two charges d) some other place e) nowhere e = 1. 6 x 10 -19 C k = 8. 99 x 109 Nm 2/C 2 2 Q d Q

Physics 241 – 11: 30 Quiz (1 point) – January 7, 2013 Two point charges are separated by distance d as shown. Where can you put a third charge of +1 C so that there is no net electric force acting on it? (Take Q > 0. ) A) to the right of charge –Q to the left of charge 2 Q B) C) between the two charges D) some other place E) nowhere e = 1. 6 x 10 -19 C k = 8. 99 x 109 Nm 2/C 2 2 Q d -Q