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 magnet, 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 magnets 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 Michael Faraday’s fi rst electric motor, 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 • Electromagnetism 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 commutator 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.