Chapter 19: Electricity

1. Chapter 19: Electricity Material on Final Exam

2. Essential Questions How do electrically charged objects interact? How can objects become electrically charged? What is an electric discharge? What is the relationship between electric charge and electric current? How do voltage, current, and resistance affect each other? What are the basic parts of an electric circuit? How do the two types of electric circuits differ?

3. What do you think? 👍👎 Protons and electrons have opposite electric charges Objects must be touching to exert a force on each other When electric current flows in a wire, the number of electrons in the wire increases Electrons flow more easily in metals than other materials In any electric circuit, current stops flowing in all parts of the circuit if a connecting wire is removed or cut The light given off by a flashlight comes from the flashlight’s batteries

4. Section 1: Electric Charge and Electric Forces Protons Neutrons Electrons • Electrical Charge • Atoms are made of three parts • _____________ • _____________ • _____________ • Focus on electrons

5. Section 1: Electric Charge and Electric Forces unbalanced space • Objects can be neutral or have a static charge, which is an ______________ - or + electric charge on an object • An electrical field is the __________ around a charged object in which another charged object experiences an electrical force

6. Section 1: Electric Charge and Electric Forces +, -, 0 opposite charges attract like charges repel • Charges Exert Forces • Three charge options • ______________________ • Charges exert forces • Law of Electrical charges states that ______________________ and _________________ _______________

8. Section 1: Electric Charge and Electric Forces • What is happening in • A? • B? • C?

9. Section 1: Electric Charge and Electric Forces Stamp Spot! Writing Prompt #1 On the left, explain the law of electrical charges in your own words. You need at least 2 lines.

10. Section 1: Electric Charge and Electric Forces attraction repulsion size distance • Electrical Force and Electrical Fields • Electrical forces are forces of ______________ or _______________ on a charged particle that is due to an electric field • How strong is the force? • Charge ________ : • Charge ____________:

11. Section 1: Electric Charge and Electric Forces

12. Section 1: Electric Charge and Electric Forces easily Copper • Conductors • An electrical conductor is a material in which charges can move ____________ • Electrons are free-moving • ____________, Aluminum, Magnesium

13. Section 1: Electric Charge and Electric Forces cannot easily move Plastic • Insulator • An electrical insulator is a material in which charges _______________________ • Electrons are “locked in” and cannot move • __________, rubber, glass, wood, air

14. Section 1: Electric Charge and Electric Forces Stamp Spot! Writing Prompt #2 On the left, Explain why it is important to have both conductors and insulators in everyday life. You need at least 2 lines.

15. Section 1: Electric Charge and Electric Forces freely Contact Induction Conduction • Transferring charge! • How to get a charge? • Change # or position of ___________! • 3 ways

16. Section 1: Electric Charge and Electric Forces wool balloon • Contact (friction) • When objects made of different materials touch, electrons tend to collect on the object that holds electrons more tightly • Ex _______ and ____________

17. Section 1: Electric Charge and Electric Forces without touching polarized • Induction • Process by which one object causes two other objects that are conductors to become charged ___________________ them • Creates charge • When electrons concentrate at one end of an object, it becomes ______________

18. Section 1: Electric Charge and Electric Forces unequal greater lower • Conduction • When conducting objects with __________ charges touch, electrons flow from the object with the ________ concentration of negative charge to the object with the ______ concentration of negative charge

20. How is charge transferred? Induction Contact Conduction ______________ ______________ _______________

21. Section 1: Electric Charge and Electric Forces created destroyed • Conservation of charge • No charges are __________ or _____________through these processes

22. Section 1: Electric Charge and Electric Forces Stamp Spot! Writing Prompt #3 In the space below, explain how we can charge an item if we cannot create or destroy charge. You need at least 2 lines.

23. Section 1: Electric Charge and Electric Forces detects charge separates • Detecting Charge • An electroscope is a device that ____________________ • As charge is applied, moves charge to metal pieces and ____________ them

24. Section 1: Electric Charge and Electric Forces contact • Electric discharge • Static electricity isan electric charged produced by ________ (friction) or induction • Called static no change • Item builds up charge and keeps it

25. Section 1: Electric Charge and Electric Forces becomes balanced lightning • Electric Discharge • Charges eventually leave • Electric Discharge the process of an unbalanced electric charge ____________ ______________ • Can be slowly • Laundry • Can be quick • Door knob, car door • ______________

26. Grounding __________ is providing a path for electric charges to flow safely into the ground Lightning

27. Section 2: Electric current and Simple Circuits movement Amps are the rateof coulombs (6x1018 e-) moving per second Amps A I electric circuit • Electric Current • Electric current is the ______________ of electrically charged particles • If we INCREASE current, we INCREASE the number of charges per second • Units: Amperes  __________ (___) • Calculations:___ • A closed, or complete, path in which an electriccurrent travels is an_____________________

28. Section 2: Electric current and Simple Circuits • Alternating Current • AC • Charges move _________________ • Ex: __________ • Direct Current • DC • All charges flow in _________________ • Ex: ____________ back and forth Outlets same direction Batteries

29. Section 2: Electric current and Simple Circuits difficult friction greater lower Ohms Ω R • Resistance • Electric Resistance is a measure of how ____________ it is for an electric current to flow in a material • “Electrical ____________” • The ___________the resistance, the ________ the current • Units: _________(__) • Calculations: ___

30. Section 2: Electric current and Simple Circuits Material Thickness Length • Resistance Factors • There are 3 items that can affect the resistance of the wire • _______________ • Insulator v. Conductor • ______________ • Thin v. Thick • ______________ • Long v. short

31. Section 2: Electric current and Simple Circuits Writing Prompt #4 • In the space below, describe the combination of the three factors that would produce a wire with the best current (means the worst resistance). You need at least 2 lines. Stamp Spot!

32. Section 2: Electric current and Simple Circuits greater greater Volts V V • Voltage • Voltage is the amount of energy the source uses to move one unit of electrons through the circuit • The ____________the voltage, the ____________ the current • Units: _______ (___) • Calculations: ___

33. Electric Circuit Calculations voltage equals resistance current • Ohm’s Law • Georg Ohm (1789-1854) first determined the relationship between current, voltage and resistance. According to Ohm’s Law, the __________ in a circuit ___________ the product of the ____________ and the _____________

34. Electric Circuit Calculations V = IR Voltage Volts Current Amps Resistance Ohms V I R Formula _________– SI unit _______ _________ – SI unit _______ _____________ – SI unit _____

35. Electric Circuit Calculations • Math Practice • What is the voltage if the current is 4 amps and the resistance is 10 ohms? • You try! • Find the current if the voltage is 0.4 V and the resistance is 2 ohms. V I R R V = IR 0.4 V = I x 2Ω I = 0.4V / 2Ω I = 0.2A V = IR V = 4A x 10Ω V = 40 Volts

36. Electric Circuit Calculations • Math Practice • The voltage of an object is 36 volts. If the current in the object is 9 A, what resistance must be used? • You try! • An object has the resistance of 20 ohms. Calculate the voltage needed to produce a current of 0.5 A. R R I I V = IR V = 0.5A x 20Ω V = 10 Volts V = IR 36V = R x 9A R = 36V / 9A R = 4 Ω

37. Electric Circuit Calculations rate converted • Formula • ________ – SI unit ________ • __________– SI unit ________ • ___________ – SI unit _______ P P = VI Power Watts Voltage Volts Current Amps V I • Electric Power • Electric Power is the _______at which electrical energy is _____________ into other forms of energy • Where the “wattage” of our lights come from!

38. Electric Circuit Calculations • Math Practice • A computer monitor draws 1.2A at a voltage of 120V. What is the power rating of the monitor? • You try! • What voltage would a light bulb have if the current is 0.5A and the power is 60W? I V I P P = VI 60W = V x 0.5 A V = 60W / 0.5A V = 120W P = VI P = 120 V x 1.2 A P = 144 Watts

39. Electric Circuit Calculations electrical energy power time • Formula • ________ – SI unit _________ • ________-SI unit ________ • ________ – SI unit ___________ E = P x t E Energy Joules Power Watts Time seconds P t • Electric Energy • The amount of _____________________ depends on the ________ of the electrical devices and the length of _______ that those devices are on

40. Electric Circuit Calculations • Math Practice • How much energy is used if a 50W appliance is run for 5 seconds? • You try! • How much energy will be needed for a 200W appliance to run for10 seconds? P P t t E = Pt E = 200W x 10s E = 2000 J E = Pt E = 50W x 5s E = 250 J

41. Electric Circuit Calculations E • Math Practice • What is the power of an appliance that uses 200,000 J of energy to run for 1000 seconds? • You try! • A 5000J appliance uses 250 W. How long will it run for? E t t E = Pt 5000J = 250W x t t = 5000J / 250W t = 20s E = Pt 200,000J = P x 1000s P = 200,000J / 1000s P = 200W

42. Electric Circuit Calculations • Electrical cost • Power companies usually charge by the kilowatt hour • Steps to find cost • Find energy: multiply appliance wattage by time (in hours) • Convert to kilowatt hours (either ÷ by 1000 or move decimal 3 times to the left) • Multiply by the cost from the electrical company • Round to two decimal places

43. Electric Circuit Calculations

44. Electric Circuit Calculations

45. Electric Circuit Calculations

46. Section 3: Describing Circuits • Generating Electrical Energy • A cell is a device that produces an electric current by converting chemical or radiant energy into electrical energy • Parts of a cell • Electrolytes—chemical that allows charges to flow • Electrode—part of the cell where charges enter and exit

47. Cell Setup

48. Section 3: Describing Circuits source Wires Device/load • Electric Circuits • An Electric circuit is a complete path around which charges can flow • There are 3 basic parts • Energy _________ • _________(where charge flows) • _______________ (change electrical energy into other forms)

49. Section 3: Describing Circuits Series Circuit only one 1 Pathway one stops none • Series Circuit • A series circuit is an electric circuit with ______________ path for an electric current to follow • If ______element ________ functioning in series circuit, _______ of the elements can operate. • Example – the wiring in a burglar alarm, holiday lights

50. Section 3: Describing Circuits Parallel Circuit more than one More than 1 path stops others operate • Parallel Circuit • A parallel circuit is an electric circuit with __________________ path, or branch, for an electric current to follow • If one element _______functioning, the ________ can still __________ • Found in most homes and businesses