1. ElectroStatics Physics NPHS Spring 2016

2. Lesson 1 Essential Question – What is an Electric Charge? Lesson Objectives –To understand the motivation behind electrostatics unit –To design and collect observations about interactions and to make conclusions from data

3. Do Now What do you know about electric charge? What do you want to know about electric charge?

4. Motivation Have you ever been shocked touching a door? Have you done laundry and noticed that your clothes stick together? Have you noticed that your hair gets frizzy when it is a dry day? Have you ever wondered why?

5. Electrostatics Activity 1 Materials –Felt/Fur –Two balloons –Plastic shopping bag Create a data table to show the following interaction –Two balloons –Two ballons rubbed with felt –1 balloons rubbed with felt and felt –Two ballons rubbed with plastic shopping bag –One ballons rubbed with plastic shopping bag, one with felt Identify patterns in your observations. Describe them carefully!

6. Building a Data Table Decide what you need to record Decide how you want to collect your data (in what order) Decide how to organize your materials so that you can find patterns in your data How will we organize our data?

7. InteractionMaterial 1Material 2Observation 1 2 3 4 5 Data Table

8. InteractionMaterial 1Material 2Observation 1Unrubbed Foam No interactions 2Foam Rubbed with felt They repel each other 3Foam Rubbed with felt Feltattract 4Foam Rubbed with plastic bag repelled 5Foam Rubbed with felt Foam Rubbed with Plastic wrap attracted Data Table

9. Conclusions What are your observations? What are your conclusions

10. System A system is a collection of two or more objects What is the system in the experiment that you just completed?

11. Statics Lesson 2 Something must have happened when the objects were rubbed together because they did not interact that way before We know that objects either are attracted to each other, repelled by each other or have not effect on each other Some objects are able to exert a force on other objects to pull or push them

12. Do Now Clothing clings together in a dryer. Why does this happen? If you have two socks and a shirt, which two would you predict will be stuck together? Is this consistent with your observations yesterday?

13. ElectroStatics Static electricity is the cause of all these occurrences The study of static electricity is called Electrostatics This is the first step in studying areas such as electric current, power and electricity. Static electricity

14. Static Charge Objects we observed that are able to apply a force to other objects are called charged objects. This was first noticed by ancient Greeks. Pieces of amber attracted or repelled one another, similar to your plastic sticks. The Greek word for amber is “electron”.

15. Movie Size of an Atom Drghonorsphysics.wikispaces.com

16. Atoms – Building Blocks of Matter Figure 1. The Bohr Model: A basic (not to scale) model of an atom displaying the nucleus, electrons and orbiting paths of electrons. copyright Atoms are composed of Protons (positively charged particles), Neutrons (neutral particles) and Electrons (negatively charged particles) The Nucleus is a dense core composed of protons and neutrons and is surrounded by “cloud” of much smaller particles – electrons. Electrons orbit the nucleus in a specific configuration

17. Key to the Periodic Table Elements are organized on the table according to their atomic number, usually found near the top of the square. –The atomic number refers to how many protons an atom of that element has. –For instance, hydrogen has 1 proton, so it’s atomic number is 1. –The atomic number is unique to that element. No two elements have the same atomic number. –Rounding the atomic weight and subracting the atomic number gives the number of neutrons –If an atom is neutral #electrons=#protons http://periodic.lanl.gov/index.shtmlhttp://periodic.lanl.gov/index.shtml - for more information about specific atoms Atomic Weight Atomic Number

18. Atoms Atoms may gain or lose electrons. In these cases, the atom as a whole is no longer neutral, and we call it an ion. A Positive Ion has a net positive charge because the atom has lost one or more electrons. A Negative Ion occurs if an atom gains one or more electrons and it has a net negative charge, and is therefore called a negative ion. Like charges repel each other, while opposite charges attract each other. In physics, we represent the charge on an object with the symbol q.

19. Fundamental properties of electric charge

20. Phet Balloon Simulation Lesson 3 Phet_Balloon_Charge.doc

21. Conduction Electrons can flow freely from particle to particle Distribution of charge caused by moving electrons Charge will be re-distributed in an object to until repulsive forces between electrons is minimized

22. Insulators Impede the free flow of electrons

23. Check your understanding One of these isolated charged spheres is copper and the other is rubber. The diagram below depicts the distribution of excess negative charge over the surface of two spheres. Label which is which and support your answer with an explanation.

24. Polarization - Conductor Negatively charged object induces electrons to move away Can becomes polarized (positive on one side, negative on the other)

25. Polarization - Insulator An insulator can become polarized as well but electrons re-distribute around nucleus. The atom is still neutral

26. Polarization of an atom

29. Check your understanding Which of the diagrams below best represents the charge distribution on a metal sphere when a positively charged plastic tube is placed nearby?

30. Grounding a Negatively Charged Object Grounding removes charge by transferring to a large electron sink (earth, human body)

31. Charge Diagrams Conduction

32. Charge Diagrams Induction

33. Charge Diagrams Polarization

34. Conduction/Induction/Polarization Name that charge (Physics Classroom Interactive) Show me your result

35. Lesson 4 Essential Question – What is an Electric Charge?

36. Lesson Objectives To understand how electric charge is transferred between objects To understand the difference between positively charged and negatively charged particles

37. Charged particle activity Take from PUM 4.7 Reason

38. Do Now Write a math statement to describe how the net charge of the material changes. –A neutral object gains 6 electrons. –A neutral object loses 9 electrons. –An object that has an excess charge of + 8 gains electrons and becomes neutral. –An object that has an excess charge of +6 gains 7 electrons. –An object that has an excess charge of -10 is neutralized. –An object that has an excess charge of -7 loses 4 electrons.

39. Lesson objective Investigate Coulomb’s law – continue with (or start) worksheets Understand that charge is quantized Example problems using Coulomb’s law

40. Electric Charge Electric charge is a physical quantity The unit for electric charge is Coulomb 1 Coulomb=amount of charge is 2 point charges placed 1 meter part to produce a force of 8.988x10 9 N

41. Electrostatic Facts Electric charge comes in two types – positive and negative; like charged objects repel and unlike charged objects attract. Historically, charge accumulated on a glass rod rubbed with silk was called positive, electric charge accumulated on a resin rod rubbed with fur – negative. Electrons and protons have basic electric charge of magnitude q = 1.6 x 10 -19 C the electron being negatively charged and the proton positively charged.

42. Electric charge is quantized Since an object cannot gain or loose a fraction of an electron, the net charge on any electron must be a multiple of the charge of an electron. Quantized means that charge can only change in discreet amounts (ie a multiple of the charge of an electron 1.6x10 -19 C)

43. How many electrons make up a charge of -20  C?

44. Do Now What is the total charge of 2200 electrons? –Hint: for each electron q=1.6x10 -19 Coulombs

45. Principle of Conservation of Charge Electrons are neither created nor destroyed but are simply transferred from one material to another. This principle is known as conservation of charge. In every event, whether large-scale or at the atomic and nuclear level, the principle of conservation of charge applies. 32.2 Conservation of Charge

46. In class activity HONORS Print pages 17-20 PUM Phyz worksheet CP

47. Coulomb’s Law

48. Example Problem 16-1 Determine the magnitude and direction of electric force on the electron of a hydrogen atom exerted by the single proton that is the atoms nucleus. Assume the average distance between the revolving electron and the proton is r=0.53x10 -10 m

49. What is the force due to gravity between the proton and electron in a hydrogen atom? Assume the average distance between the revolving electron and the proton is r=0.53x10 -10 m Mass Proton =1.6726 x10 -27 kg Mass Electron (at rest) =1.6749x10 -27 kg

50. Similarities?

51. A comparison between Electric and Gravitational forces Electric ForceGravitational Force Equation Force Characteristics Attract and Repel Only Attract Non-contact ConstantK=9x10 9 Nm 2 /C 2 G=6.67x10 -11 Nm 2 /kg 2 MagnitudeMuch Stronger Force

52. Example problems using charge What is the force on a +2.3  C charge that lies 3.7 m to the left of a -5.1  C charge?.

53. How far is a +4.5 x10 -3 C charge from a -8.2x10 -3 C charge if there is a force of 13N between them?

54. Thought Question You are given 2 balloons. One has twice as much charge on it than the other. –When brought together, which experience the larger force and why? –If the amount of charge on one is doubled, what do you think happens to the forces between them?

55. Another thought question Which graph best represents the electrostatic force between an alpha particle (net charge of +2) and a positively charged nucleus as a function of their distance of separation?

56. Conductors and Dielectrics Conductors: These are materials in which charged particles can move freely from one place to another. In metals these particles are electrons. Dielectrics: These are materials in which electrically charged particles cannot move freely. However, the electric charge in the particles (atoms and molecules) of which the material is made can shift slightly within the particles. This small redistribution can cause an excess of one type of charge on one side of the object and an excess of the other type of charge on the opposite side of the object.

57. A substance is classified as a conductor or an insulator based on how tightly the atoms of the substance hold their electrons. The conductivity of a metal can be more than a million trillion times greater than the conductivity of an insulator such as glass. In power lines, charge flows much more easily through hundreds of kilometers of metal wire than through the few centimeters of insulating material that separates the wire from the supporting tower. 32.4 Conductors and Insulators

58. Semiconductors are materials that can be made to behave sometimes as insulators and sometimes as conductors. Atoms in a semiconductor hold their electrons until given small energy boosts. This occurs in photovoltaic cells that convert solar energy into electrical energy. Thin layers of semiconducting materials sandwiched together make up transistors. 32.4 Conductors and Insulators

59. Do Now Two conducting spheres have an excess of negatively charged particles and are placed very far apart from one another. –Draw a picture of the spheres when they are far apart –Draw a picture of the spheres when they are close together but not touching –Draw a picture of the spheres when they are moved far apart again.

60. Principal of Superposition What if several charges exist? –The net force on any one of the charges is a vector sum of the forces on that charge due to each other –Determined experimentally

61. Review of Vector Addition 1. Pythagorean theorem

62. Trigonometry Review SohCahToa

63. Example Three charged particles are arranged in a line. Calculate the net electrostatic force on particle 3 due to the other two charges. --+ D=0.3m D=0.2 m Q1=-8.0  C Q1=3.0  C Q1=-4.0  C

64. Example 2