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A 1. conducting bar moves to the left at a constant speed v on two conducting rails joined at the left in a constant magnetic field B=0.5 T as shown. A current I is induced in the indicated direction. Which one of the following directions is that of the magnetic field? A) B) C) D) E) toward the right toward the left parallel to the long axis of the bar into the page out of the page 2. A conducting bar moves to the left at a constant speed v= 1 m/s on two conducting rails in a constant magnetic field B=0.5 T. The rails are joined at the left as shown. Originally the loop is h= 0.5 m high and l=1 m long. The current in the loop is I = 0.25 A. What is the loop's resistance? A) B) C) D) E) 0.25 Ohm 0.5 Ohm 1 Ohm 2 Ohm 5 Ohm Page 1 3. A metal ring is dropped from rest below a bar magnet that is fixed in position as suggested in the figure. An observer views the ring from below. Which one of the following statements concerning this situation is true? A) As the ring falls, an induced current will flow counterclockwise as viewed by the observer. B) As the ring falls, an induced current will flow clockwise as viewed by the observer. C) As the ring falls, there will be an induced magnetic field around the ring that appears counterclockwise as viewed by the observer. D) As the ring falls, there will be an induced magnetic field around the ring that appears clockwise as viewed by the observer. E) Since the magnet is stationary, there will be no induced current in the ring. 4. A circular coil has 100 turns and a radius of 0.1 m. The coil is used as an ac generator by rotating it in a 0.500 T magnetic field, as shown in the figure. At what angular speed should the coil be rotated so that the maximum emf is 314 V? A) B) C) D) E) 28 rad/s 50 rad/s 130 rad/s 200 rad/s 490 rad/s Page 2 5. Two coils share a common axis as shown in the figure. The mutual inductance of this pair of coils is 6.0 mH. If the current in coil 1 is changing at the rate of 3.5 A/s, what is the magnitude of the emf generated in coil 2? A) 5.8 * 10 4 V B) 1.7 * 10 3 V C) 3.5 * 10 3 V D) 1.5 * 102 V E) 2.1 * 102 V 6. Which one of the following statements concerning transformers is false? A) Their operation makes use of mutual induction. B) They are an application of Faraday's and Lenz's laws. C) A transformer can function with either an ac current or a steady dc current. D) A transformer that steps down the voltage, steps up the current. E) A transformer that steps up the voltage, steps down the current. Use the following to answer question 7. A small power plant produces a voltage of 6.0 kV and 150 A. The voltage is stepped up to 240 kV by a transformer before it is transmitted to a substation. The resistance of the transmission line between the power plant and the substation is 75 . 7. What is the current in the transmission line from the plant to the substation? A) 3.8 A B) 5.2 A C) 6.4 A D) 7.0 A E) 7.5 A Page 3 8. When a radio telescope observes a region of space between two stars, it detects electromagnetic radiation that has a wavelength of 0.21 m. This radiation was emitted by hydrogen atoms in the gas and dust located in that region. What is the frequency of this radiation? A) 7.1 * 101 0 Hz B) 2.1 * 101 4 Hz C) 3.0 * 108 Hz D) 6.9 * 101 1 Hz E) 1.4 * 109 Hz 9. The peak value of the electric field component of an electromagnetic wave is E. At a particular instant, the intensity of the wave is of 0.020 W/m2 . If the electric field increased were to 5E, what would be the intensity of the wave? A) 0.020 W/m2 B) 0.10 W/m2 C) 0.25 W/m2 D) 0.50 W/m2 E) 1.0 W/m2 10. What would the speed of an observer be if a red (4.688 * 101 4 Hz) traffic light appeared green (5.555 * 101 4 Hz) to the observer? A) 4.445 * 108 m/s B) 2.219 * 108 m/s C) 8.438 * 107 m/s D) 5.548 * 107 m/s E) 2.890 * 106 m/s Page 4 11. A linearly polarized beam of light is incident upon a group of three polarizing sheets which are arranged so that the transmission axis of each sheet is rotated by 45 with respect to the preceding sheet as shown. What fraction of the incident intensity is transmitted? A) B) C) D) E) 1/8 1/4 3/8 1/2 3/4 12. The radius of curvature of a spherical convex mirror is 52 cm. What is its focal length? A) +26 cm B) 26 cm C) +52 cm D) 52 cm E) +104 cm Use the following to answer question 13. An object is placed in front of a concave spherical mirror as shown below. The three rays 1, 2, and 3, leave the top of the object and, after reflection, converge at a point on the top of the image. Ray 1 is parallel to the principal axis, ray 2 passes through F, and ray 3 passes through C. Page 5 13. Which ray(s) will reflect back on itself (themselves)? A) 1 only B) 2 only C) 3 only D) both 1 and 2 E) 1, 2, and 3 14. A concave mirror in an amusement park has a radius of curvature of 4.0 m. A child stands in front of the mirror so that she appears 2.5 times taller than her actual height. If the image is upright, how far is she standing from the mirror? A) 1.2 m B) 3.5 m C) 2.8 m D) 4.0 m E) 7.0 m 15. The speed of light in material A is 1.25 times as large as it is in material B. What is the ratio of the refractive indices, nA/nB, of these materials? A) 1.50 B) 1.25 C) 1.00 D) 0.90 E) 0.800 16. A grizzly bear is sitting on a rock in the middle of a calm river when she observes a fish directly below her. If the fish is 30 cm long, what is the apparent length of the fish? The index of refraction of water is 1.33. A) 40 cm B) 71 cm C) 62 cm D) 53 cm E) 45 cm Page 6 17. Complete the following statement: The term dispersion refers to the fact that the index of refraction of certain materials A) depends on the Brewster angle. B) depends on the wavelength of light. C) depends on the angle of incidence. D) depends on the intensity of light. E) depends on the polarization of light. 18. An object is placed at the focal point of a thin diverging lens of focal length - f. What is the image distance? A) f B) 2f C) 1/f D) f/2 E) at an infinite distance 19. When an object is placed 15 cm from a lens, a virtual image is formed. Which one of the following conclusions is incorrect? A) The lens may be a convex or concave. B) If the image is upright the lens must be a diverging lens. C) If the image is reduced, the lens must be a diverging lens. D) If the lens is a diverging lens, the image distance must be less than 15 cm. E) If the lens is a converging lens, the focal length must be greater than 15 cm. 20. Which one of the following statements is true concerning a magnifying glass? A) It produces a virtual image. B) It produces an inverted image. C) It can be made from a diverging lens. D) The image distance will be less than the object distance. E) The object must be placed outside the focal point of the lens. Page 7 Answer Key - PractriceExam2B 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. E C A D E C A E D D B B C A E A B D B A Page 8 ... View Full Document

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