1. Unit 10 Chapter 13

2. You will have carpal tunnel syndrome by the end of this unit if you don’t learn how to summarize the information contained in this powerpoint.

3. Think of all the ways electricity can be found in your daily life. Could you survive without electricity?

5. Electric charge is an electrical property of matter that creates a force between objects. All matter is made of atoms Atoms are composed from 3 essential particles Neutrons – in the nucleus with a neutral charge Proton – in the nucleus with a (+) charge Electron – outside the nucleus with a (-) charge

6. SI unit of electric charge is the coulomb, C Electrons and protons have exactly the same amount of charge… 1.6 x 10 -19 C Because they are oppositely charged. Protons is a +1.6 x 10 -19 C Electrons is a -1.6 x 10 -19 C If an object has excess electrons then it has an electric charge. The net electric charge is always a multiple of 1.6 x 10 -19 C.

7. Atoms become charged by gaining or losing electrons Static electricity is the accumulation of excess electric charges on an object

8. Law of Conservation of Charge Charge may be transferred from object to object but it cannot be created or destroyed

9. Opposites attract and like charges repel Charges can act at great distances Any charge placed in an electric field will be pushed or pulled by the field

11. Electrons move more easily through conductors like metals Electrons do no move easily through insulators such as plastic, wood, rubber, and glass

14. Really dry air

15. With a big enough build up of charge, electricity WILL flow

18. Like say half a megavolt trying to pass through a wire

20. A conductor is a material that transfers charge easily It allows the charges to flow Example: metal An insulator is a material that does not transfer charge easily It will not allow the charges to flow Examples: cardboard, glass, silk, and plastic

21. Three main methods Charging by contact Charging by Induction Static Discharge

22. Done by touching or rubbing Example: feet rubbing the carpet then touching a metal door knob

23. Electrons move because of a nearby charged object Example: negatively charged balloon near your sleeve causes your sleeve to be positively charged

24. A transfer of charge through the air between two objects because of the buildup of a static electricity – a spark! Example: lightning

25. Grounding – using a conductor to direct the charge into the ground It an important part of electrical safety! The presence of a charge can be determined by an electroscope

27. Electric force is the force of attraction or repulsion between objects due to charge It is the reason why some clothes cling together when you take them out of the dryer It is part of what holds an atom together It also plays a part in chemical bonding Without electric force, life itself would be impossible

28. The electric force between 2 charged objects varies depending on the amount of charge on each object and the distance between them Acts through a field Electric field is the region around a charged object in which other charged objects experience an electric force

29. Regardless of the charge, electric field lines never cross one another

31. Electrical potential energy is the potential energy of a charged object due to its position in an electric field Potential difference is the change in the electrical potential energy per unit charge SI unit for potential difference is the volt (V) which is equivalent to 1 joule per coulomb Often called voltage

32. The flow of charges through a wire or conductor is called electric current Current is the rate that electric charges move through a conductor SI unit of current is Amperes (A or amp)

33. Charges flow from high voltage to low voltage A voltage difference is the push that causes charges to move Voltage difference is measured in volts (V) For charges to flow, the wire must always be connected in a closed path or circuit

34. Cell is a device that is a source of electric current because of a potential difference, or voltage between the terminals Dry cell – standard battery – produces a voltage difference by a chemical reaction Wet cell – car battery – produces a voltage difference by chemical reaction Wall sockets – AC – produced at a generator

35. Electrochemical – Electrons transferred between different metals immersed in an electrolyte Uses – common batteries and automobile batteries Photoelectric and photovoltaic – Electrons are released from a metal when struck by light of sufficient energy Uses –satellites, calculators, and streetlights

36. Thermoelectric – Two different metals are joined together, and the junctions are held at different temperatures, causing electrons to flow. Uses – Thermostats for furnaces and ovens Piezoelectric – Opposite surfaces of certain crystals become electrically charged when under pressure. Uses – crystal microphones and headsets, computer keypads

39. Conventional current is the movement of positive charge It is current made of positive charge that would have the same effect as the actual motion of charge in the material

40. Resistance is the ratio of the voltage across a conductor to the current it carries The tendency for a material to oppose the flow of electrons, changing electrical energy into thermal energy and light All materials have some resistance

41. SI unit of resistance is ohms (Ω) It is equal to volts per ampere Resistor is a special type of conductor used to control current Making wires thinner, longer, or hotter increases resistance

42. light bulbs make use of resistance

45. I = V R I – current (A) V – voltage (V) R – resistance (Ω)

46. What is the resistance of a wire that has a current of 1.4 A in it when it is connected to a 6.0 V battery? R = V I

47. What is the resistance of a wire that has a current of 1.4 A in it when it is connected to a 6.0 V battery? R = V I = 6.0 V = 4.3 Ω 1.4 A

48. An electric space heater is plugged into a 120 V outlet. A current of 12.0 A is in the coils in the space heater. What is the resistance of the coils?

49. R = V I = 120 V = 10 Ω 12.0 A

50. A steam ion has a current of 9.17 A when plugged into a 120 V outlet. What is the resistance of the steam iron?

51. R = V I = 120 V = 13 Ω 9.17 A

52. Practice problems……………………..

53. 120.12V

54. 4.8V

55. 116.5V

56. 119.56V

57. 4.55V 1.5V per battery

58. 2.9A

59. 15A

60. 4.79A

61. 5.2A

62. 230.77Ω

63. 179.2 Ω

64. 5.74A

65. Conductors have low resistances They allow the electrons to flow easily and therefore have a low resistance

66. Some materials become superconductors below a certain temperature Certain metals and compounds have zero resistance when their temperature falls below the critical temperature The critical temperature varies between - 272 o C and -123 o C Examples – tin, mercury, and some metallic compounds containing barium, copper, and oxygen

67. Insulators have high resistance to charge movement They are used to prevent electric current from leaking Examples - plastic coating around copper wire of an electric cord keeps the current from escaping into the floor or your body

69. Electric circuit is an electrical device connected so that it provides one or more complete paths for the movement of charges Closed circuit is one in which there is a closed-loop path for electrons to follow Open circuit is one without a complete path, there is no charge flow and therefore no current

70. Schematic diagram is a graphic representation of an electric circuit or apparatus, with standard symbols for the electrical devices

71. Circuits rely on generators at power plants to produce a voltage difference across the outlet, causing the charge to move when the circuit is complete

72. Series describes a circuit or portion of a circuit that provides a single conducting path Parallel describes components in a circuit that are connected across common points, providing two or more separate conducting paths

73. The current has only one loop to flow through The parts of the series circuit are wired one after another so the amount of current is the same through every part

77. Open circuit – If any part of a series circuit is disconnected, no current flows through the circuit Example – Christmas lights

78. Contain two or more branches for current to move through Individual parts can be turned off without affecting the entire circuit Example – circuits in a house

81. Electrical energy is the energy associated with electrical charges, whether moving or at rest The energy may come from a battery or a power plant Electric Power Power = current x voltage P = IV SI unit for power is the watt (W)

82. A flashlight has a potential difference of 3.0 V. The bulb has a current of 0.50 A. What is the electric power used by the flashlight? P = IV = 3.0 V x 0.50 A = 1.5 W

83. What is the current in a 60 W light bulb when it plugged into a 120 V outlet?

84. I = P V = 60 W = 0.5 A 120 V

85. Use parallel circuits Each branch receives the standard voltage difference Electricity enters your home at the circuit breaker or fuse box and branches out to the rest of your house

86. Electric fuse – contains a small piece of metal that melts if current becomes too high and breaks the circuit Circuit breaker – uses a magnet or bimetallic strip (a strip with two different metals welded together) that responds to current overload by opening the circuit. It protects a circuit from current overloads Used in many homes and businesses