sign in sign up
<<
Home , DC motor

CHAPTER 12 rEVIEW k/u Knowledge/Understanding t/I Thinking/Investigation c Communication A Application

knowledge Match each name on the left with the most appropriate For each question, select the best answer from the four contribution on the right. alternatives. 7. (a) Magnes of (i) showed that a magnetic 1. Which of these best describes the location of Earth’s Magnesia fi eld surrounds a current- magnetic fi eld? (12.1) k/u carrying wire (a) only inside Earth (b) Hans Christian (ii) created the fi rst electric (b) surrounding Earth Oersted motor (c) outside Earth’s atmosphere (c) André-Marie (iii) ancient Greek shepherd (d) both inside and surrounding Earth Ampère who discovered magnetite 2. Th e fi rst compasses were most likely made of which (d) Michael (iv) found that two wires with material? (12.1) k/u Faraday opposite currents created a repulsive force (12.1, (a) soft iron 12.2, 12.4, 12.5) k/u (b) magnesium (c) copper Write a short answer to each question. (d) magnetite 3. Magnetic fi eld lines 8. What fi elds are present around a massive , such as Earth? What technology could be used to (a) sometimes cross each other detect the presence and direction of at least one of the (b) point from south to north outside a magnet fi elds? (12.1) k/u (c) are farther apart where the magnet is stronger 9. A current is directed into a straight conductor (d) point from south to north inside a magnet oriented perpendicular to the page. Th e current goes k/u (12.1) into the page. What shape and in which direction are 4. Which best describes the force created when the the magnetic fi eld lines? (12.2) k/u north poles of two are brought together? 10. Explain how the use of fi elds can be applied to k/u (12.1) transmitting electrical energy without wires. (a) resonant (12.3) k/u (b) negligible 11. Th e attraction of two wires with current going in the (c) repulsive same direction tells us what about their magnetic (d) attractive fi elds? (12.4) k/u 5. When using the electron fl ow model to illustrate 12. Solenoids are oft en used as controllable bar magnets. electrical current in a straight wire, what rule is used Describe how the magnetic fi eld lines of a bar magnet to determine the direction of the resulting magnetic and the magnetic fi eld lines of a solenoid are similar fi eld? (12.2) k/u to each other. (12.4) k/u c (a) right-hand rule for a straight conductor 13. State the right-hand rule for a solenoid. (12.4) k/u (b) left -hand rule for a straight conductor 14. In ’s fi rst , what (c) conventional current method interacted with the magnetic fi eld of the bar magnet (d) right-hand rule for solenoids to cause the motion of the motor? (12.5) k/u 6. A version of the right-hand rule can be used to 15. (a) According to the motor principle, what happens determine which of the following? (12.2, 12.4, to a current-carrying conductor as it cuts across 12.5) k/u external magnetic fi eld lines? (a) direction of the magnetic fi eld created by a (b) What factors determine the magnitude of this eff ect current-carrying straight wire on the current-carrying conductor? (12.5) k/u (b) direction of the magnetic fi eld created by a 16. One of the fi rst practical uses of the motor principle current-carrying solenoid was the development of analog meters. What is the (c) direction of the force on the current-carrying main advantage of an analog meter compared to a conductor of an electric motor modern digital meter? (12.5) k/u (d) all of the above

580 Chapter 12 • NEL

7381a_Phy_Ch12_pp546-585.indd 580 1/6/11 1:40:02 PM 17. (a) What did the invention of the split ring 21. Describe why iron fi lings are useful for understanding allow a DC motor to do? magnetic fi elds. (12.1) k/u c (b) What other developments have improved the 22. Describe how various magnets are used in the Maglev design of DC motors? (12.6) k/u train in Shanghai and in what direction the magnetic forces are acting. (12.1) c A understanding 23. Many physicists had hypothesized that electric 18. Earth has both a magnetic fi eld and a gravitational currents produce magnetic fi elds, but Hans Christian fi eld. (12.1) k/u Oersted was able to confi rm the hypothesis. (12.2) k/u (a) What is the diff erence between these two fi elds with (a) How did Oersted confi rm that electric currents respect to the direction of the forces they cause? produce magnetic fi elds? (b) What is the diff erence between these two fi elds (b) What further details did Oersted’s method of testing with respect to the materials that they act upon? his hypothesis provide about these magnetic fi elds? 19. (a) Draw the magnetic fi eld lines created by two bar 24. What is the main similarity between the behaviour of magnets held close together with one north and charged particles and that of magnetic poles? (12.2) k/u one south pole facing each other. 25. (a) How do the models of conventional current and (b) Draw the magnetic fi eld lines created by two bar electron fl ow diff er from each other? magnets held close together with their north (b) How do conventional current and electron poles facing each other. fl ow aff ect how we determine the direction of a (c) How would your illustration from (b) change magnetic fi eld around a straight wire? (12.2) k/u if the magnets were held with their south poles 26. Using the page as a frame of reference and applying facing each other? (12.1) k/u c the right-hand rule, determine the following: 20. In the images in Figure 1, there is a mistake in the (12.2) t/I fi eld lines. Copy each image and correct the mistake. (a) What is the direction of the current that produces (12.1) t/I a counterclockwise magnetic fi eld on the page? (b) What is the direction of the magnetic fi eld produced by a current fl owing into the page?

N 27. Determine the direction (clockwise or counterclockwise) of the magnetic fi elds produced by the currents in Figure 2. (12.2) t/I S N N S S

(a) (b) (a) (c) Figure 2

28. Which direction on the compass will the needle point for each scenario in Figure 3? (12.2) t/I

N

conventional N conventional N current current W E W E S S S

(b) (a) (b) Figure 1 Figure 3

Ontario Physics 11 U Ontario Physics 11 U 0176504338 0176504338 Ontario Physics 11 U Ontario Physics 11 U FN C12Q-F004a-OP11USBFN C12Q-F004c-OP11USB0176504338 0176504338 CO Crowle Art COGroup Crowle Art GroupFN C12Q-F001a-OP11USBFN C12Q-F001b-OP11USB NEL Chapter 12 review 581 Deborah Crowle Deborah CrowleCO Crowle ArtCO Group Crowle Art Group Pass 1st pass Pass 1st pass Deborah Crowle Deborah Crowle Approved Approved Pass 2nd pass Pass 2nd pass 7381a_Phy_Ch12_pp546-585.indd 581 1/6/11 1:40:03 PM Not Approved Not Approved Approved Approved Not Approved Not Approved

Ontario Physics 11 U Ontario Physics 11 U Ontario Physics 11 U 0176504338 0176504338 0176504338 FN C12Q-F004b-OP11USB FN C12Q-F002a-OP11USBFN C12Q-F002b-OP11USB CO Crowle Art Group CO Crowle ArtCO Group Crowle Art Group Deborah Crowle Deborah Crowle Deborah Crowle Pass 1st pass Pass 1st pass Pass 1st pass Approved Approved Approved Not Approved Not Approved Not Approved 29. Determine the direction of the current for the 34. Explain how the right-hand rule for a solenoid magnetic fi eld shown in Figure 4. (12.2) t/I helps us to understand the operation of a solenoid. (12.4) k/u 35. (a) Describe the eff ect of running a current through a wire suspended between the north pole of one magnet and the south pole of another magnet. (b) What is the eff ect of reversing this current? (c) Draw a diagram of the magnetic fi eld lines of both of these cases and the direction of the resultant eff ects. (12.5) t/I c Figure 4 36. Describe what is shown in Figure 6 and explain how this simple diagram defi nes the fundamentals of the 30. What conclusion did Ampère draw from his experiments motor principle. Be sure to discuss the interaction with two current-carrying wires? (12.4) k/u between the magnetic fi eld lines shown. (12.5) c A 31. Two parallel wires are each carrying a current. Th ere is a magnetic force of attraction between the two S N S N wires. (12.4) t/I c (a) What do we know about the directions of the currents, based on the magnetic force? (b) What kind of magnetic force would be produced if both of the currents in the wires were reversed? (b) (c) What kind of magnetic force would be produced if only one current was changed? Figure 6 (d) What would the eff ect on the magnetic force be if the currents were increased? 37. (a) Explain the right-hand rule for the motor Ontario Physics 11 U (e) What would the eff ect on the magnetic force be if principle. (b) Explain how you would orient your right hand 0176504338 one current was increased and the other current was switched off ? to determine the direction of the force produced FN C12Q-F003-OP11USB 32. (a) Use your own words to describe a solenoid. if the current moves toward the right and the CO Crowle Art Group external magnetic fi eld is pointing upward. (b) Draw a current-carrying solenoid. Label the Deborah Crowle direction of the current, the magnetic fi eld lines, (c) Does the description in (b) result in a force into t/I A Pass 1st pass and the north and south poles of the solenoid. the page or out of the page? (12.5) Approved (12.4) k/u c 38. Galvanometers are used in circuits to measure k/u c A Not Approved 33. Th ere is a mistake in Figure 5. Copy the image and electrical signals. (12.5) correct the mistake. (12.4) t/I A (a) What two specifi c measurement devices contain a galvanometer? What electrical property does each Ontario Physics 11 U measure? (b) Explain for each measurement device how the 0176504338 direction of galvanometer is included in the circuit. FN conventionalC12Q-F006-OP11USB current 39. (a) Using your own words, explain the diff erence CO NGI between a galvanometer and a DC motor. (b) What technology was used to make the transition Pass 5th pass between a galvanometer and a DC motor, and Approved how does it work? Not Approved (c) Draw and label a diagram of a simple DC motor. Be sure to include both moving and stationary components. (12.5, 12.6) c A

Figure 5

582 Chapter 12 • Electromagnetism NEL

7381a_Phy_Ch12_pp546-585.indd 582 1/6/11 1:40:05 PM

Ontario Physics 11 U 0176504338 FN C12Q-F005-OP11USB CO NGI

Pass 5th pass Approved Not Approved 40. (a) List the major components of a DC motor. State 49. (a) A subwoofer uses a solenoid (voice coil) and a whether each component is a stationary or a permanent magnet to create vibrations of the rotating part. speaker cone. Describe the interaction between (b) What is the name for the stationary parts of a DC the solenoid (voice coil) and the permanent motor? What is the name for the rotating parts of magnet. a DC motor? (12.6) t/I (b) If the quality of the speaker is in part defi ned 41. (a) List three ways that the design of a DC motor can by the strength of the solenoid, what properties be improved. should the solenoid of a high-quality speaker k/u t/I c A (b) If one of these three improvements is taken to an have? (12.4) extreme, it becomes undesirable. Which is it and 50. Study Figure 7 carefully. Determine the magnetic what is the risk that makes it less desirable than poles on each of the coils at the bottom of the cores. the other two? (12.6) k/u What is the shape of the magnetic fi eld similar to? t/I A 42. Using your own words, describe the problem of a split (12.4) ring commutator with a single split and describe the solution that DC motor designers came up with to overcome it. (12.6) k/u c 43. Explain the development of DC motors, beginning with Oersted’s experiment and concluding with modern DC motors. (12.2, 12.5, 12.6) k/u c A 44. Discuss the strengths and weaknesses of each of the following medical imaging technologies: X-rays, ultrasound, and magnetic resonance imaging. (12.7) k/u A

Analysis and Application Figure 7 45. Using your own words, describe how the aurora 51. An MRI can use a magnetic fi eld that is produced by borealis is an eff ect of Earth’s magnetic fi eld that is one of three types of technology: an , observed as a display of light. (12.1) k/u c A a permanent magnet or a superconducting magnet. 46. If a compass is moved away from a current-carrying An electromagnet would need many windings and conductor, eventually the needle of the compass will a large to produce a strong enough return to pointing toward Earth’s magnetic north magnetic fi eld for an MRI machine. Why would the t/I A pole. (12.2) k/u c electromagnet not be a desirable choice? (12.4) (a) What property of magnetic fi eld lines does this 52. Michael Faraday’s experiment that resulted in the fi rst illustrate? electric motor was based on the idea of movement (b) How does the needle’s return to Earth’s magnetic between a magnetic object and an external magnetic north pole illustrate this property of fi eld lines? fi eld. What is the fundamental diff erence between his motor and a compass, which is also a magnetic object 47. Describe three ways an electromagnet can be more moving due to an external magnetic fi eld? (12.5) c A advantageous than a permanentScience magnet,Physics 11and provide a useful example for each.ISBN: (12.4) ISBN c #A 0176504338 53. In which direction will the galvanometer needle move in Figure 8? (12.5) t/I A 48. (a) Name a household objectFN that uses a magnet.C12Q-F12-OP11USB (b) Does this object useCO its magnet to interactDave with McKay Illustration another magnet or does it use its magneticdhm fi eld to produce a force onPass a metallic object?First Pass 10/09/23 (c) Is the magnet used inApproved this object a permanent magnet or an electromagnet?Not Approved (d) Draw a diagram of how this object’s magnet N S is used. Be sure to include fi eld lines. (12.4) k/u t/I c

Figure 8

NEL Chapter 12 review 583

7381a_Phy_Ch12_pp546-585.indd 583 1/6/11 1:40:05 PM

Science Physics 11 ISBN: ISBN # 0176504338 FN C12Q-F15-OP11USB CO Dave McKay Illustration dhm Pass First Pass 10/09/23 Approved Not Approved 54. Figure 9 shows a single-loop DC motor. Determine 58. Suppose that instead of using permanent magnets the direction of rotation of the loop. (12.6) T/I A for the external magnets in a DC motor you used . Further suppose that the electromagnets are connected to the same external circuit as the brushes of the motor. Would it be possible to reverse the direction of rotation of this motor design? Explain. (12.4, 12.6) T/I A 59. (a) Describe how a gasoline-electric hybrid car uses an electric motor. (b) Describe the primary bene t of using electric motors in automobiles. (c) What factors prevent a hybrid car from being completely pollution free? (12.6) K/U A

Evaluation 60. Maglev trains use magnets to reduce friction and to produce forward motion.  is is a replacement for wheels and steam engines. (12.1) K/U A Figure 9 (a) Describe a possible use of magnets to replace 55. What should the external magnet poles be in order a component of the automobile. For example, for the motor in Figure 10 to spin counterclockwise? describe how traditional brakes might be replaced (12.6) T/I A by magnetic brakes. (b) Describe one bene t and one drawback of this use of magnets over conventional parts. (c) Describe how some other familiar technology could bene t from the use of magnets. 61.  is chapter discusses both natural magnetic phenomena and technologies where can be manipulated by humans. Compare natural Science Physics 11 magnetic occurrences with any of the human-made ISBN: ISBN # 0176504338 technologies discussed. List the di erences and the FN C12Q-F13-OP11USB Figure 10 similarities. (12.1, 12.4, 12.6, 12.7) K/U C A CO Dave McKay Illustration 56. A DC motor can be made to spin faster or slower by 62. Compare two innovations that use electromagnetism. dhm altering the current. A variable resistor is a device that Describe the ways electromagnetism is used to Pass Second Pass 10/10/08 can vary its electrical resistance by typically rotating produce the desired e ect and the impact of the Approved a dial. How could a motor and a variable resistor be technologies on daily life and society at large. Not Approved used in a variable speed electric drill? Explain your (12.4, 12.6, 12.7) K/U A answer. (12.6) T/I A Refl ect on Your Learning 57. Copy and complete Table 1 by lling in what change to the variable will cause either an increase or decrease 63. Describe several ways in which Oersted’s experiments in the strength/speed of the motor. (12.6) K/U T/I with electric current have shaped technology today. Table 1 C A Increase the Decrease the 64. To understand the impact of electromagnetism motor strength/ motor strength/ on our everyday lives, keep a journal of all your Variable speed speed interactions with DC motors for an entire day. Science Physics 11 current Remember that computer fans and hard drives, DVD ISBN: ISBN # 0176504338 players, windows, and vacuum cleaners, number of loops FN C12Q-F14-OP11USB among many other objects, all use DC motors to CO Dave McKay Illustrationtype of make objects rotate. Make your list as complete as possible. K/U C A dhm strength of Pass First Pass 10/09/23 external magnets Approved Not Approved 584 Chapter 12 • Electromagnetism NEL

7381a_Phy_Ch12_pp546-585.indd 584 1/19/11 1:53:17 PM 65. Pick an everyday item that uses electromagnetism. 70. Solenoids are used in subwoofers, electric bells, and Describe how your daily life would change without cars, among other applications. Research other uses that item. For example, without speakers, we would for solenoids. Write a short report that includes a have no cellphones. C A discussion of the application and a diagram of how the solenoid is employed. T/I C A go to nelson science Research 71. A mass spectrometer (Figure 11) measures the mass 66. The Large Hadron Collider (LHC) is one of the and relative concentrations of atoms and molecules largest scientific undertakings in human history. It using magnetic fields. For example, a scientist can relies heavily on electromagnets to control the path take a sample of pure carbon and, by using a mass and the speed of particles within the accelerator. spectrometer, find that it contains two different forms Choose one of the following topics and write a short of carbon (isotopes): carbon-12 and carbon-13. report about your findings: The mass spectrometer can also be used to identify • the use of electromagnets within the LHC the quantity of compounds in a mixture. Research • the research goals of the particle accelerator how a mass spectrometer uses magnetic fields to • the recent results of testing at the LHC T/I C A separate compounds or elements in a mixture. Also include in your research some of the incredible 67. The aurora borealis and aurora australis (the northern detection capabilities of a mass spectrometer when and southern lights) have been topics of discussion attached to a gas chromatograph. Write a short report in both mythology and science. Research an ancient of your findings. T/I C A mythological explanation for the northern lights. Write a paragraph comparing the mythological explanation with the current scientific understanding of the aurora. T/I C A 68. dreamed of transmitting electrical energy without using grids. Research some of the potential applications of wireless electricity today and the consequences that these applications could have on everyday life. Create a slide presentation that summarizes your findings. T/I C A 69. Many companies are developing and producing electric vehicles. Research one company. T/I C A (a) Write a brief history of the company. (b) Does the company boast any specific technological advances over its competitors? If yes, what is it? If no, how does the company plan to gain a competitive edge? Figure 11 (c) Write a paragraph or two describing any of the company’s major successes or failures. (d) What is your impression of the vehicles produced by this company? Be sure to back up your arguments with reasoning.

NEL Chapter 12 Review 585

7381a_Phy_Ch12_pp546-585.indd 585 1/6/11 1:40:09 PM