Lecture 1.1

1. Lecture 1.1

2. PRS rf PRS RF Student Clicker/Remote Two line display for indicating response and status of receipt Scroll Keys Send/Enter Backspace Alpha, Numeric and T/F Keys AAA batteries used to keep future costs down. Setup Key Diagnostics include Battery level %

3. PRS rf Turn on Clicker - Battery symbol displayed Stop scan by hitting “ * ” on the keypad Hit “ * ” again which takes you to the Setup Menu Scroll Up to ID: Hit “Send/Enter” key (green) Type ID number Hit “Send/Enter” Hit “ * ” to exit Setup Menu ID now stored in the unit (for Non Loaner units) Can now rescan by selecting New Class Scan, or by turning unit off and on. Sign on Process (First Time)

4. Sample question • I am a: • Freshman • Sophomore • Junior • Senior • None of above

5. Chapter 26. Electric Charges and Forces

6. Electric Charges and Forces The electric force is one of the fundamental forces of nature. Controlled electricity is the cornerstone of our modern, technological society. Chapter Goal: To develop a basic understanding of electric phenomena in terms of charges, forces, and fields.

7. Topics: Developing a Charge Model Charge Insulators and Conductors Coulomb’s Law The Field Model Chapter 26. Electric Charges and Forces

8. Chapter 26. Reading Quizzes

9. Question: What is the SI unit of charge? • Coulomb • Faraday • Ampere • Ohm • Volt

10. What is the SI unit of charge? • Coulomb • Faraday • Ampere • Ohm • Volt

11. A charge alters the space around it. What is this alteration of space called? • Charged plasma • Charge sphere • Electric ether • Electric field • Electrophoresys

12. A charge alters the space around it. What is this alteration of space called? • Charged plasma • Charge sphere • Electric ether • Electric field • Electrophoresys

13. If a negative charged rod is held near a neutral metal ball, the ball is attracted to the rod. This happens • because of magnetic effects. • because the ball tries to pull the rod’s  electrons over to it. • because the rod polarizes the metal. • because the rod and the ball have  opposite charges.

14. If a negative charged rod is held near a neutral metal ball, the ball is attracted to the rod. This happens • because of magnetic effects. • because the ball tries to pull the rod’s  electrons over to it. • because the rod polarizes the metal. • because the rod and the ball have  opposite charges.

15. The electric field of a charge is defined by the force on • an electron. • a proton. • a source charge. • a test charge.

16. The electric field of a charge is defined by the force on • an electron. • a proton. • a source charge. • a test charge.

17. Chapter 26. Basic Content and Examples

18. Charge Model Objects can be charged by rubbing; charged objects attract small objects, such as foams, or paper shreds. Charge can be transferred from on object to another. Two kinds of charges: positive and negative Likely charged objects repel each others, oppositely charged objects attract each other. (Note: Both positive and negative charged objects attract neutral charge. ) How do we know that an object is charged: electroscope. Opposite charges cancel each other. (that is why we call then + and - charges)

19. End of lecture

20. Lecture 1.2

21. Announcement A new lab session for phy222 is open now M011   Wednesday 6:00-8:00 PM  Class # 34159

22. Review of Last Lecture: Charge Model 1. Objects can be charged by rubbing; charged objects attract small objects, such as foams, or paper shreds. 2. Charge can be transferred from on object to another. 3. Two kinds of charges. We define: black plastic (PVC) to be positively charged, and clear plastic (acrylic) to be negatively charged 4. Likely charged objects repel each others, oppositely charged objects attract each other. Both positive and negative charged objects attract neutral charge. 5. How do we know that an object is charged: electroscope. 6. Opposite charges cancel each other. (that is why we call then + and - charges)

23. Remember that a rubbed clear plastic rod is negatively charged. To determine if an object has negative charge, you need to • see if the object attracts a charged black plastic rod. • see if the object repels a charged clear plastic rod. • Both A and B. • Either A or B.

24. Remember that a rubbed clear plastic rod is negatively charged. To determine if an object has negative charge, you need to • see if the object attracts a charged black plastic rod. • see if the object repels a charged clear plastic rod. • Both A and B. • Either A or B.

25. Two Kinds of Matters: Conductors & Insulators • Conductors: where charge can freely move, immediately spread over. • Examples: metals (soda can), ionic (salt) solutions, human body, earth,… • Insulators: charge can not move, they are instead localized. • Pastic, pure water, rubber, foams… • Both conductors and insulators can be charged. • The difference is how charges move in these matters.

27. Mechanism of electroscope • how an electroscope works. • First charge spread over conductor • Then like charges repel

28. Lightening: the air becomes an conductor (Dielectric breakdown) Grounding: connecting to earth

29. Matters Consist of Atoms

30. Atoms and Electricity • An atom consists of a very small and dense nucleus    surrounded by much less massive orbiting electrons. • The nucleus is a composite structure consisting of    protons, positively charged particles, and neutral neutrons. • The atom is held together by the attractive electric force    between the positive nucleus and the negative electrons. • Electrons and protons have charges of opposite sign but    exactlyequal magnitude. (miracle?) • This atomic-level unit of charge, called the fundamental    unit of charge, is represented by the symbol e.

31. Charge quantization • A macroscopic object has net charge (e>0 by convention) • (always integer multiple of e) • Where Np and Ne are the number of protons and electrons    contained in the object. • The process of removing or adding an electron from the electron cloud of an atom is called ionization.

33. Rank in order, from most positive to most negative, the charges qa to qe of these five systems. • qa = qb > qe > qc > qd • qa > qe > qd > qc > qb • qe > qa > qd > qb > qc • qd > qc > qe > qa = qb • qd > qc > qe > qa > qb

34. Rank in order, from most positive to most negative, the charges qa to qe of these five systems. • qa = qb > qe > qc > qd • qa > qe > qd > qc > qb • qe > qa > qd > qb > qc • qd > qc > qe > qa = qb • qd > qc > qe > qa > qb

35. Atomic Structure of Insulators • The electrons in the insulator    are all tightly bound to the    positive nuclei and not free to    move around. • Charging an insulator by    friction leaves patches of    molecular ions on the surface,    but these patches are    immobile.

36. Atomic Structure of Conductors • In metals, there is a fraction of electrons that are free to wander about through the entire solid. • These electron bahave as liquid. • The solid as a whole remains    electrically neutral, but the    electrons are now like a    negatively charged liquid    permeating an array of    positively charged ion cores.

37. Charge Polarization

38. Charge Polarization in Conductors

39. Why leaves open up?

40. Polarization in Insulators:The Electric Dipole

41. The Electric Dipole

42. Charging by Induction, Step 1

43. Charging by Induction, Step 2

44. Charging by Induction, Step 3

45. An electroscope is positively charged by touching it with a positive glass rod. The electroscope leaves spread apart and the glass rod is removed. Then a negatively charged plastic rod is brought close to the top of the electroscope, but it doesn’t touch. What happens to the leaves? • The leaves get closer together. • The leaves spread further apart. • The leaves don’t move. • One leaf moves higher, the other lower.

46. An electroscope is positively charged by touching it with a positive glass rod. The electroscope leaves spread apart and the glass rod is removed. Then a negatively charged plastic rod is brought close to the top of the electroscope, but it doesn’t touch. What happens to the leaves? • The leaves get closer together. • The leaves spread further apart. • The leaves don’t move. • One leaf moves higher, the other lower.

47. End of lecture

48. Announcement From the Textbook Publisher The company dealing with your $10 rebate went bankrupt recently, which means that you will not be able to get your rebate. Trying to make it up for you, the publisher offers every student a free copy of “Tutorials in Introductory Physics”. Please come up and get a copy.

49. Lecture 2.1

50. Review of Last Week’s Lectures + and - charges, like charge repel, opposite charge attract Charges can be detected by electroscope Neutral objects contain equal amounts of positive and negative charges. Charge redistribution inside neutral objects: polarization Two kinds of matter: Conductors, where charge can freely move Insulators, where charge is localized At microscopic level, charges are carried by electron and proton. Charge is quantized, and conserved.