CHAPTE1 Review K/U Knowledge/Understanding T/I Thinking/Investigation C Communication A Application Knowledge For each question, select the best answer from the four alternatives. 1. Which of the following is a unit of electrical power? (11.1) K/U (a) joule (b) watt (c) kilowatt hour (d) coulomb 2. What are you measuring when you measure voltage in a circuit using a voltmeter? (11.3) K/U (a) the amount of energy of individual electrons (b) the difference in the amount of energy associated with a coulomb of electrons between two points in a circuit (c) the difference in the number of electrons between two points in a circuit (d) the difference in the flow of electrons between two points in a circuit 3. A hydroelectric power plant transforms which of the following into electrical energy? (11.1) K/U (a) nuclear energy (b) thermal energy (c) kinetic energy (d) solar energy 4. Which of the following devices uses the most power? (11.1) K/U (a) plasma TV (b) cellphone (c) laptop computer (d) central air conditioner 5. Which type of power plant technology is least efficient? (11.1) K/U (a) fossil fuel (b) solar (c) hydro (d) nuclear 6. Which device is used to measure the electric potential difference in a circuit? (11.3) K/U (a) ammeter (b) ohmmeter (c) voltmeter (d) potential meter 7. When an electric current is present in a circuit, which particles move? (11.5) K/U (a) electrons (b) protons (c) neutrons (d) all of the above 8. What electrical component does the symbol in Figure 1 represent? (11.6, 11.7) K/U (a) connecting wire (b) battery (c) lamp (d) resistor Figure 1 9. Which of the following expressions is equivalent to resistance? (11.7) K/U (a) V 3 I I (b) V (c) V I 1 (d) IV Indicate whether each statement is true or false. If you think the statement is false, rewrite it to make it true. 10. Burning coal can cause global warming and acid rain. (11.2) K/U 11. Coal gasification is a technology that captures carbon dioxide leaving the smokestack, compresses it, and transports it by pipeline to a storage location deep underground. (11.2) K/U 12. Electric potential is a measure of how much electric potential energy is associated with each charge. (11.3) K/U 13. Conventional current is the movement of charge from negative to positive. (11.4) K/U 14. Direct current is the flow of electrons in a back-andforth manner through a circuit. (11.5) K/U 15. The symbol I is used to represent electric current. (11.5) K/U 540 Chapter 11 Electricity and Its Production NEL
16. Kirchhoff s current law (KCL) states that the current entering a junction is equal to the current exiting a junction in a circuit. (11.6) K/U 17. Superconductors are materials with almost infinite electrical resistance. (11.7) K/U 18. For resistors in series, the total resistance is given by 1 R series 5 1 1 1 1 1 1 # # # # (11.8) K/U Write a short answer to each question. 19. A circuit consists of three loads connected in series. Using one of Kirchhoff s laws, express the potential difference across the voltage source in terms of the potential differences across each of the loads. (11.6) K/U 20. Three resistors,,, and, are placed in parallel. Write an expression for the total resistance, R, of the circuit. (11.8) K/U 21. Draw the circuit symbol that represents a battery. (11.6) K/U Understanding 22. A nuclear power plant has an efficiency of 35 %. If the core nuclear reactants can provide 12 000 MW of power, how much electrical power does the power plant produce? (11.1) T/I 23. Calculate the energy, in kilowatt hours, required by a 60.0 W light bulb that operates for 3.0 h. (11.1) T/I 24. Calculate the energy, in kilowatt hours and joules, needed by a 450 W window air conditioner that operates for 48 h. (11.1) T/I 25. Calculate the amount of power required to charge a battery if 1200 J of energy is transferred in 5 min. (11.1) T/I 26. A solar power plant has an efficiency of 16 % and produces 30.0 MW of electrical power. (11.1) T/I (a) How much total power does the power plant require as input in order to produce an output of 30.0 MW? (b) How much energy is lost by being converted to thermal energy each second? 27. Calculate the electric potential difference between the negative and positive terminals of a battery if 1080 J of electric potential energy is transformed to move 120 C of charge between the terminals. (11.3) T/I 28. The potential difference across the terminals of a light bulb is 120 V. If the bulb transforms 480 J of energy, how much total charge is moved across the terminals? (11.3) T/I 29. A 35 W light bulb is on for 2.5 h. If the potential difference across the bulb s terminals is 120 V, how much total charge moves through the bulb while it is on? (11.1, 11.3) T/I 30. Redraw the circuit in Figure 2 to include the placement of an ammeter to measure, a voltmeter to measure, and an ohmmeter to measure. (11.3, 11.5, 11.7) T/I C Figure 2 31. A washing machine is plugged into a 240 V source and uses 2.0 kwh of energy each load. (11.1, 11.3, 11.5) T/I (a) How much total charge is moved through the machine for each load? (b) If each load takes 35 min, how much power does the machine use? Answer in watts. (c) If each load takes 35 min, how much current does the machine draw? Answer in amperes. 32. A student has connected an ammeter into a circuit as shown in Figure 3. Redraw the figure to show a proper connection for an ammeter. (11.5) T/I C V source Figure 3 A 33. Calculate the amount of current in a wire if 0.75 C of electrons pass through a point in 1.7 min. (11.5) T/I 34. How many coulombs pass through a wire that carries a current of 3.2 A for 5.0 h? (11.5) T/I NEL Chapter 11 Review 541
35. Calculate the time required for 3 C of charge to pass through a resistor if the current is 750 ma. (11.5) T/I 36. Draw a circuit with a battery and two lamps in parallel. (11.6) K/U C 37. Draw a circuit with a battery and a lamp that is in series with two resistors that are in parallel. (11.6) K/U C 38. In the circuit in Figure 4, if the potential difference across the battery is 9.0 V, calculate if (a) V 1 5 3.0 V (b) V 1 5 (11.6) T/I 43. Four resistors are placed in series in a circuit. If the resistances are 5 2.3 Ω, 5 4.3 Ω, 5 0.85 Ω, and R 4 5 1.2 Ω, what is the total resistance of the circuit? (11.8) T/I 44. Three resistors are connected in parallel in a circuit. If the resistances are 5 2.1 Ω, 5 7.2 Ω, and 5 4.5 Ω, calculate the equivalent resistance of the circuit. (11.8) T/I 45. Calculate the total resistance in the circuit in Figure 7 if the resistor values are as follows: 5 6.1 Ω, 5 13 Ω, and 5 27.2 Ω. (11.8) T/I V 1 Figure 4 39. In the circuit in Figure 5, 5 7.5 ma. Calculate if (a) 5 4.3 ma (b) 5 (11.6) T/I Figure 7 46. In the circuit in Figure 8, the potential difference across the battery is 18 V. V 1 is 7.0 V and 5 30.0 Ω. Calculate the values of,, and the current through the circuit. (11.9) T/I V 1 Figure 5 40. Calculate the resistance of a load with a voltage of 60 V and a current of 750 ma. (11.7) T/I 41. An 80.0 Ω resistor carries 0.85 ma of current. What is the potential difference across the resistor? (11.7) T/I 42. The circuit in Figure 6 has a current of 0.50 ma. If V 1 is 4.55 V and the potential difference across the battery is 12 V, what are the two resistances, and? (11.7) T/I Figure 8 47. For the circuit in Figure 9, 5 3.0 Ω and 5 60.0 Ω. The potential difference across the battery is 22 V, and V 1 is 12 V. Calculate,,, and. (11.9) T/I V 1 V 1 Figure 9 Figure 6 542 Chapter 11 Electricity and Its Production NEL
Analysis and Application 48. (a) A hydroelectric power plant produces 1200 MW of power at 85 % efficiency. A nuclear power plant produces 1200 MW of power at 40 % efficiency. How much more power is wasted in the nuclear power plant than in the hydroelectric power plant? (b) It is difficult to compare the efficiencies of different power plants because some plants transform energy twice: the first time from the source energy to thermal energy and the second time from thermal energy to electrical energy. Name two power plant technologies that can be compared more directly. (11.1) T/I A 49. A coal-fired power plant produces 2500 MW of power with 46 % efficiency. When carbon capture technology is installed, the efficiency decreases to 42 %. Calculate the amount of extra power lost to the carbon capture technology. (11.1, 11.2) T/I A 50. A battery takes 2.0 MJ of energy to charge. If the charger operates using 40.0 W of power but only transfers 90 % of the energy to the battery, how long does it take to charge the battery? (11.1) T/I 51. A 60.0 W incandescent light bulb is only 11 % efficient at producing light (the rest is converted into thermal energy). The light bulb is operating for 2.0 h. Calculate how much energy is input to the bulb and how much energy is output as light energy. (11.1) T/I 52. A 14 W CFL bulb uses 5.1 kwh of electrical energy at an efficiency of 75 %. Calculate the time that the CFL bulb is operational and the electrical energy output. Answer in hours and kilowatt hours respectively. (11.1) T/I 53. In the circuit in Figure 10, V source 5 20.0 V, 5 30.0 Ω, and 5 12.0 Ω. In 10.0 s, how many coulombs of charge pass through the circuit? (11.5, 11.9) T/I 54. In the circuit in Figure 11, V source 5 5.0 V, 5 7.0 Ω, and 5 3.55 V. (11.5, 11.9) T/I (a) What is the value of? (b) How long will it take for 12 C of charge to pass through the circuit? V source Figure 11 55. In the circuit in Figure 12, V source 5 12 V, 5 5.0 Ω, 5 16 Ω, and 5 30.0 Ω. (11.5, 11.9) T/I (a) After 7.0 s, how many coulombs of charge pass through the circuit? (b) After 12 s, how many coulombs of charge pass through? V source Figure 12 56. In the circuit in Figure 13, V source 5 15 V, V 1 5 9.0 V, 5 500.0 ma, and 5 30.0 Ω. (11.5, 11.9) T/I (a) What are and? (b) How long does it take for 20.0 C of charge to pass through the circuit? V 1 V source V source Figure 10 Figure 13 NEL Chapter 11 Review 543
57. A repair technician is using an ohmmeter to check for open circuits in a computer system. The computer system is connected to a power supply that is turned on. The technician records resistance values and then turns the power supply off. He then repeats his measurements of resistance values. Would the resistance values be the same in both measurements? Which scenario is correct for measuring resistance values? (11.7) T/I 58. A student has three resistors, with resistances of 75 Ω, 50 Ω, and 30 Ω. Draw a diagram to show how the student can build a circuit with a total resistance of 60 Ω. (11.8) T/I C 59. A student has four resistors, with resistances of 7.00 Ω, 12.0 Ω, 24.0 Ω, and 28.0 Ω. Draw a diagram to show how the student can build a circuit with a total resistance of 13.6 Ω. (11.8) T/I C 60. Derive an expression for power (P) in terms of current (I ) and potential (V ). (11.1, 11.3, 11.5, 11.7) T/I C 63. In the circuit in Figure 15, 5, 5 150 Ω, and R 4 5 200.0 Ω. If V source 5 15 V and 5 4.0 A, find (a) and (b) (11.9) T/I V source Figure 15 64. In the circuit in Figure 16, V 1 5 V 4, V source 5 50.0 V, 5 100.0 Ω, 5 2, I source 5 0.250 A, and 2 5 3I 4. (11.9) T/I (a) What are the values of R 4,,, and I 4? (b) What are the values of and V 3? R 4 61. A student measures the following values for voltage across and current through a circuit: V 1 V 3 Current (I ) Potential (V ) 0.080 ma 10 V 0.097 ma 12 V 0.111 ma 14 V V source Figure 16 I 4 R 4 V 4 0.129 ma 16 V 0.144 ma 18 V (a) Plot the points on a graph of voltage versus current. Draw the line of best fit. (b) What is the slope of the line of best fit and what does it mean? (11.8) K/U T/I C 62. In the circuit in Figure 14, 5 30.0 Ω, 5 50.0 Ω, 5 R 4 5 60.0 Ω, and V 1 5 12 V. (11.9) T/I (a) What is the total current through the circuit? (b) What is V source? 65. In the circuit in Figure 17, 5 2, 5 R 4, 2 5 5, V source 5 34 V, and 5 110 ma. (11.9) T/I (a) Find the values of,,, and R 4. (b) Find I. V source R 4 V 1 I Figure 17 V source R 4 Figure 14 544 Chapter 11 Electricity and Its Production NEL
Evaluation 66. Make a list of five common household items that use electricity, and determine the average voltage, current, and resistance for each by looking at the label. Rank these items in order of the energy they consume in one day of average use in your household. (11.3, 11.5, 11.6) T/I C A 67. A common household outlet has a small night light plugged into the top part of the receptacle. A power bar is plugged into the bottom part of the receptacle, and plugged into the power bar are a lamp, a computer, and a cellphone charger. Draw a circuit diagram for this outlet. Use resistor symbols for the computer and cellphone charger and be sure to label all parts. Why might it be a poor idea to include the lamp and cell phone charger on the same power bar as the computer? (11.7, 11.8) T/I C A Reflect on Your Learning 68. More than half of Ontario s electrical energy is generated through nuclear power. Do you approve or disapprove of using this technology to produce your electricity? Would you rather use an alternative source of energy? Write several paragraphs supporting your view on how electrical energy should be produced in Ontario. K/U C A 69. Making power plants more efficient is an ongoing and expensive process. Suggest things that you could do at home to reduce your dependence on electricity. K/U C A 70. Electric potential difference is a challenging concept for students to grasp. What aspects did you find challenging and what helped you gain a deeper understanding? K/U C 71. What aspect of Kirchhoff s voltage law did you find particularly challenging? Explain what helped you get past your difficulties. K/U C 72. Connecting resistors in parallel lowers the total or equivalent resistance. Many students find it challenging to understand how the addition of resistors in parallel can lower the equivalent resistance. How have you come to understand this concept? K/U C Research go to nelson science 73. You can purchase several different types of light bulbs to use at home. Research and compare the environmental impacts of compact fluorescent, incandescent, and LED technologies. T/I C A (a) What materials are used to make each light bulb? Are there environmental concerns about these materials? (b) Compare the amount of energy used in a 10-year period for each light bulb. Which bulb has more of an environmental impact over the 10-year period? (c) What are the environmental impacts of disposing of the light bulbs? Do they require special treatment? Which type of bulb produces the most waste? 74. Resistors are used in virtually every electronic device. Research the different types of resistors. Find out what they look like, what they are made of, what their resistance is, how they are labelled, and what they are used for. Summarize your research in a report or poster. T/I C A 75. One of the most overlooked pollutants from power plants is waste heat that is generally given off into bodies of water. If the average temperature of that body of water increases by even a few degrees, it can have major effects on the ecosystem. Research the average amount of waste heat that different power plants may produce and the environmental impacts that are being dealt with today. T/I C A 76. Determine the average potential difference in a bolt of lightning. What causes this potential difference, and how much current can a bolt of lightning carry? Find an estimate for the average duration of each type of bolt and determine the total charge carried. Include theories for the causes of each type of lightning. T/I C A 77. The oceans are often overlooked as energy sources, but with development of new technologies, clean energy can be generated using both the tides and ocean currents. Research these new technologies. Discuss any effects these technologies may have on the environment, and decide whether they are feasible methods of energy production. T/I C A NEL Chapter 11 Review 545