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Unit 3 review Modified True/False Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true. ____ 1. The easiest way to neutralize a conductive material is to use a process called grounding. _________________________ ____ 2. The quantity of an electric charge is measured in coulombs. _________________________ ____ 3. Static electricity describes an electric charge that is stationary on the surface of a material. _________________________ ____ 4. An object becomes charged if it contains unequal numbers of electrons and protons. _________________________ ____ 5. It is possible to charge an electroscope without touching it. _________________________ ____ 6. The unit of measurement that refers to the quantity of charge passing through a point in a conducting wire per unit of time is the coulomb. _________________________ The following diagram illustrates an electrochemical cell with an ammeter and a voltmeter connected in the circuit. ____ 7. In the diagram above, C represents the source for the electrical circuit. _________________________ ____ 8. In the circuit illustrated above, the conductor is labelled A. _________________________ ____ 9. In a circuit with three identical resistors in parallel, the sum of the currents through the three resistors is equal to the total current through the circuit. _________________________ ____ 10. The total resistance of a series circuit consisting of three resistors, each of which has a resistance of 3 . _________________________ Multiple Choice Identify the choice that best completes the statement or answers the question. , is 1 ____ 11. When you rub different materials with wool or cotton and then hold the materials together, you can determine a. the properties of electric charges. b. the speed of movement of electrons. c. the sizes of electromagnetic fields. d. which materials have a magnetic field. The following diagram illustrates the charge on three different objects, A, B, and C. ____ 12. In the illustration above, object A is a. positively charged. b. negatively charged. c. neutral. d. a semiconductor. The following diagram illustrates a simple circuit. ____ 13. In the circuit illustrated above, the current flows a. from the positive terminal of the battery through the circuit to the negative terminal. b. from the negative terminal of the battery through the circuit to the positive terminal. c. only when the switch is open. d. Both B and C. ____ 14. The symbol I is used to represent a. load. b. current. c. volts. d. power. ____ 15. The following diagram illustrates a circuit that consists of a battery, a switch, and a lamp. The battery has a voltage of 9 V and the lamp has a resistance of 6 . What is the current through the circuit? a. 0.67 A c. 1.5 A b. 3 A d. 72 A ____ 16. Which of the following graphs shows the relationship between potential difference (V) and current (I) through a simple electrical circuit in which the resistance remains constant? a. c. b. d. The following diagram illustrates an electrochemical cell circuit. ____ 17. Which of the following statements are true of the circuit shown above? I. Electrons flow from the positive terminal to the negative terminal through the electrolyte. II. Electrons flow from the negative terminal to the positive terminal through the conducting wire. III. Bubbles of aluminum gas will form on one electrode. IV. Positive ions escape from the negative electrode. V. Positive ions escape from the positive electrode. VI. Positive ions escape from the electrolyte. a. I and III b. II, III, and V c. II and IV d. II and VI ____ 18. A change is made to the resistance of an element in an electrical circuit. As a result of the change, the current through a load doubles, and the potential difference across the load is cut in half. What change was made to the resistance? a. The resistance was reduced by three quarters to one quarter of its original value. b. The resistance reduced by one half. c. The resistance was unchanged. d. The resistance doubled. ____ 19. Three identical resistors are connected in series to a 6 V power supply. An ammeter is used to determine the total current (I) through the 6 V power supply circuit. Which equation will give the resistance of the second resistor? a. Resistance = 6 V I b. Resistance = 6 V I c. Resistance = 6 V 3 I d. Resistance = 6 V 3 I ____ 20. On a home’s electricity meter, what is measured in kilowatt-hours? a. current c. resistance b. energy d. cost Matching Match each term to one of the following definitions. a. electrostatic spray painter d. ionizer b. lightning rod e. electroscope c. photocopier ____ 21. a machine that uses a metal that is a conductor in visible light and an insulator in the dark ____ 22. a conductor that protects buildings during storms ____ 23. a device that uses electric charge to remove pollutants from smokestacks ____ 24. a device that gives cars and trucks a smooth paint finish ____ 25. a device that is used to observe the presence of electric charge Match the total resistance to one of the following arrangements of resistors. a. one 30 resistor b. one 50 resistor in series c. two 10 resistors in parallel d. three 5 resistors in series e. three 3 resistors in parallel f. two 30 resistors in series ____ 26. 1 ____ 27. 5 ____ 28. 15 ____ 29. 30 ____ 30. 60 Short Answer 31. List four conductors and four insulators. 32. The illustration above shows a lemon being used in an electrochemical cell. a) What does this tell you about the properties of lemon juice? b) How would you investigate what other fruits or vegetables share this property? 33. What is the relationship between the resistance and the power rating of an electrical device connected to a constant potential difference? (Hint: Use the equations P=IV and V=IR to answer the question. You may need to rearrange the equations.) Problem 34. The following diagram shows the charges that accumulate in two different balloons when they are rubbed. What does this diagram tell you about the properties of the material from which each balloon is made? Explain. 35. a) Explain what happens to a neutral electroscope when a positively charged rod is brought close to, but not touching the electroscipe and then is pulled away. b) Would your observations of the leaves of the electroscope change if a negatively charged rod were used instead? Explain. 36. You are packing for a camping trip. Your younger brother helps put the batteries into your flashlight. All the batteries are new and fully charged. When you reach your destination, however, you find that the flashlight does not work. What might have gone wrong? Unit 3 review Answer Section MODIFIED TRUE/FALSE 1. ANS: OBJ: KEY: 2. ANS: OBJ: KEY: 3. ANS: OBJ: KEY: 4. ANS: OBJ: KEY: 5. ANS: OBJ: KEY: 6. ANS: T Section 7.1 LOC: C5 grounding T Section 7.1 LOC: C5 coulomb T Section 7.1 LOC: C5 static charge T Section 7.1 LOC: C5 static charge T Section 7.2 LOC: C5 electroscope | induction F, ampere PTS: 1 DIF: TOP: Static Charge Easy PTS: 1 DIF: TOP: Static Charge Easy PTS: 1 DIF: TOP: Static Charge Average PTS: 1 DIF: TOP: Static Charge Easy PTS: 1 DIF: TOP: Electric Force Average PTS: TOP: 7. ANS: OBJ: KEY: 8. ANS: 1 DIF: Easy Electric Current T Section 8.2 LOC: C6 source | circuit components F, B OBJ: KEY: PTS: TOP: Section 8.2 LOC: C6 ampere 1 DIF: Average Electric Current PTS: TOP: 9. ANS: OBJ: KEY: 10. ANS: 1 DIF: Easy Electric Current T Section 9.1 LOC: C7 parallel circuit F, 9 OBJ: KEY: PTS: TOP: Section 8.2 LOC: C6 circuit components | conductor 1 DIF: Average Series and Parallel Circuits PTS: 1 DIF: Average TOP: Series and Parallel Circuits OBJ: Section 9.1 LOC: C7 KEY: series circuit | resistance MULTIPLE CHOICE 11. ANS: LOC: 12. ANS: LOC: 13. ANS: LOC: A C5 C C5 B C6 PTS: TOP: PTS: TOP: PTS: TOP: 1 DIF: Difficult Static Charge 1 DIF: Easy Static Charge 1 DIF: Average Electric Current OBJ: KEY: OBJ: KEY: OBJ: KEY: Section 7.1 properties of electric charges Section 7.1 electron transfer Section 8.2 current 14. ANS: LOC: 15. ANS: LOC: 16. ANS: LOC: 17. ANS: LOC: KEY: 18. ANS: LOC: 19. ANS: LOC: 20. ANS: LOC: B PTS: C6 TOP: C PTS: C6 TOP: D PTS: C6 TOP: C PTS: C6 TOP: electrochemical cell A PTS: C6 TOP: C PTS: C7 TOP: B PTS: C8 TOP: 1 DIF: Average OBJ: Resistance and Ohm's Law KEY: 1 DIF: Average OBJ: Resistance and Ohm's Law KEY: 1 DIF: Difficult OBJ: Resistance and Ohm's Law KEY: 1 DIF: Difficult OBJ: Electric Potential Energy and Voltage Section 8.3 current Section 8.3 Ohm's law Section 8.3 Ohm's law Section 8.1 1 DIF: Difficult Resistance and Ohm's Law 1 DIF: Difficult Series and Parallel Circuits 1 DIF: Average The Power of Electricity OBJ: KEY: OBJ: KEY: OBJ: KEY: Section 8.3 Ohm's law Section 9.1 series circuit Section 9.2 household energy use 21. ANS: LOC: 22. ANS: LOC: 23. ANS: LOC: 24. ANS: LOC: 25. ANS: LOC: C C5 B C5 D C5 A C5 E C5 PTS: TOP: PTS: TOP: PTS: TOP: PTS: TOP: PTS: TOP: 1 Electric Force 1 Static Charge 1 Static Charge 1 Static Charge 1 Electric Force OBJ: KEY: OBJ: KEY: OBJ: KEY: OBJ: KEY: OBJ: KEY: Section 7.2 photocopier Section 7.1 grounding Section 7.1 applications of static charge Section 7.1 applications of static charge Section 7.2 electroscope 26. ANS: LOC: 27. ANS: LOC: 28. ANS: LOC: 29. ANS: LOC: 30. ANS: LOC: E C7 C C7 D C7 A C7 F C7 PTS: TOP: PTS: TOP: PTS: TOP: PTS: TOP: PTS: TOP: 1 DIF: Difficult Series and Parallel Circuits 1 DIF: Difficult Series and Parallel Circuits 1 DIF: Difficult Series and Parallel Circuits 1 DIF: Difficult Series and Parallel Circuits 1 DIF: Difficult Series and Parallel Circuits OBJ: KEY: OBJ: KEY: OBJ: KEY: OBJ: KEY: OBJ: KEY: Section 9.1 parallel circuit Section 9.1 parallel circuit Section 9.1 series circuit Section 9.1 series circuit Section 9.1 series circuit MATCHING DIF: Average DIF: Average DIF: Average DIF: Average DIF: Average SHORT ANSWER 31. ANS: Any four of the following: Conductors: Copper, aluminum, salt water, gold, iron, nickel, magnesium, mercury, platinum, silver, tungsten, silicon, carbon, Earth, the human body, humid air, nichrome Insulators: Amber, plastic, rubber, pure water, silk, glass, ebonite, cotton, fur, paper, porcelain, sulfur, wood, wool PTS: 4 DIF: Easy OBJ: Section 7.1 LOC: C5 TOP: Static Charge KEY: conductors | insulator 32. ANS: a) This tells you that lemon juice is an electrolyte (it can conduct electricity). b) Replace the lemon in the circuit with other fruits or vegetables and observe the ammeter. Any current indicates that the fruit or vegetable can conduct electricity. PTS: 1 DIF: Easy OBJ: Section 8.1 LOC: C6 TOP: Electric Potential Energy and Voltage KEY: electrochemical cell 33. ANS: Power is the product of current and voltage. Given a constant voltage, power increases only with an increase in the current. Current is voltage divided by resistance. Given a constant voltage, current increases only with a reduction in resistance. Therefore, the power of a device increases with a decrease in its resistance. That is, a high-power device is one with a low resistance. PTS: 3 DIF: Difficult TOP: The Power of Electricity OBJ: Section 9.2 LOC: C8 KEY: resistance | power PROBLEM 34. ANS: 1) In balloon A the charge remains in one place. This indicates that balloon A is made of an insulating material such as rubber. 2) In balloon B the charges move freely over the surface of the balloon. This indicates that balloon B is made of a conducting material such as a metallic substance. PTS: 1 DIF: Average OBJ: Section 7.2 LOC: C5 TOP: Electric Force KEY: laws of static charge | properties of electric charges 35. ANS: a) Electrons will move up from the leaves to the bulb of the electroscope since they are attracted to the positively charged rod. The leaves will move apart from each other because they both carry a positive charge, so they repel each other. When the rod is pulled away, the leaves will move back to their original position as the electrons move back to an even distribution within the electroscope. b) No. Electrons would move from the bulb to the leaves since they would be repelled by the negative charge of the rod, but the leaves would still move apart because they would both carry negative charges, which would repel each other. PTS: 2 DIF: Difficult OBJ: Section 7.2 LOC: C5 TOP: Electric Force KEY: electroscope | induction 36. ANS: One or more of the batteries may have been inserted so that the positive and negative terminals were reversed. This breaks the circuit and prevents current from flowing through the flashlight bulb. PTS: 1 DIF: Average OBJ: Section 8.1 TOP: Electric Potential Energy and Voltage LOC: C6 KEY: electrochemical cell