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Unformatted text preview: PHYSICS 222 - Fall 2010 FINAL EXAM: December 14, 2010 - 7:00pm--9:00pm Name (printed): __________________________________________________________ Recitation Instructor: ________________________________________________ Section #: _______ INSTRUCTIONS: This exam contains 25 multiple-choice questions, plus two extra-credit questions, each worth 4 points. The last four questions are the laboratory final. Choose one answer only for each question. Choose the best answer to each question. Answer all questions. Allowed material: Before turning over this page, put away all materials except for pencils, erasers, rulers and your calculator. There is a formula sheet attached at the end of the exam. Other copies of the formula sheet are not allowed. Calculator: In general, any calculator, including calculators that perform graphing, is permitted. Electronic devices that can store large amounts of text, data or equations (like laptops, palmtops, pocket computers, PDA or e-book readers) are NOT permitted. If you are unsure whether or not your calculator is allowed for the exam, ask your TA. How to fill in the bubble sheet: Use a number 2 pencil. Do NOT use ink. If you did not bring a pencil, ask for one. In case you are using a new bubble sheet: Write and fill in the bubbles corresponding to: - Your last name, middle initial, and first name. - Your ID number (the middle 9 digits on your ISU card) - Special codes K to L are your recitation section. (Honors sections: H1 10 ; H2 23). Always use two digits (e.g. 01, 09, 11, 13) Please turn over your bubble sheet when you are not writing on it. If you need to change any entry, you must completely erase your previous entry. Also, circle your answers on this exam. Before handing in your exam, be sure that your answers on your bubble sheet are what you intend them to be. You may also copy down your answers on a piece of paper to take with you and compare with the posted answers. You may use the table at the end of the exam for this. When you are finished with the exam, place all exam materials, including the bubble sheet, and the exam itself, into your folder and return the folder to your recitation instructor. No cell phone calls allowed. Either turn off your cell phone or leave it at home. Anyone answering (or using) a cell phone must hand in their work immediately; their exam is over. Best of luck, Paul Canfield and Paula Herrera Note that questions are numbered 55 through 81. 55. A series RLC circuit is connected to a 220 V rms, 50 Hz wall socket. The current in the circuit has an rms value of 15 A and leads the voltage by a phase angle of 34. Find |XL-XC|, the total reactance of the circuit, and compare the magnitudes of XL and XC. A. 12 and XL < XC B. 8.2 and XL < XC C. 8.2 and XL > XC D. 12 and XL > XC E. 15 and XL > XC 56. The magnetic field of a plane electromagnetic wave in vacuum has the following form: ! "$ $ ! ! " "# # = $!% &'(# $" + !# + & " )% At y = 0 and t = 0, the electric field of this wave points in the ________ direction. The wave propagates in the ________ direction. A. +x, +y B. +x, -y C. -x, -y D. +x, -z E. +x, +z 57. Two fish, A and B, are swimming in a quiet lake at a depth of 5.00 m, but separated by a distance d. Fish A is however quite surprised when he looks up to the surface and sees a twin of fish B hovering above the surface, somewhere in the air. What is the minimum value of d for this to happen? (nwater = 1.33) 5.00 m ? B A d A. 5.25 m B. 6.61 m C. 8.05 m D. 9.00 m E. 11.4 m 58. A beam of natural light traveling along the x axis shines upon a stack of three polarizing sheets. All the sheets are parallel to the yz plane. The first polarizer's axis is aligned with the y axis. The second polarizer's axis makes an angle of 30 with the y axis. The third polarizer's axis is aligned with the z axis. What is the ratio between the intensity of the beam after the three polarizers and the initial intensity? A. 0 B. 0.042 C. 0.094 D. 0.28 E. 0.50 59. A thin film of oil (n = 1.44) floats on water (n = 1.33). Red light with a wavelength in air of 700 nm is shone vertically on the film. When reflected light is observed from above, what is the smallest thickness of the film that will result in total constructive interference? A. 122 nm B. 175 nm C. 243 nm D. 350 nm E. 486 nm 60. An optical system consists of a diverging lens and a convex mirror. They both have the same focal distance f < 0. The lens and the mirror are coaxial and spaced a distance d = 2|f|. An object is located at a distance d to the left of the lens. The final image produced by this optical system is: A. Real, upright and larger than the object. B. Real, inverted and smaller than the object. C. Virtual, upright and smaller than the object. D. Virtual, inverted and smaller than the object. E. Virtual, inverted and larger than the object. 61. A charged balloon is placed close to an isolated, neutral metal bar as shown to the right. Which of the following is true? A. The bar acquires a net charge by induction, and exerts an attractive force on the balloon. B. The bar acquires a net charge by induction, and exerts a repulsive force on the balloon. C. The bar is polarized and exerts an attractive force on the balloon. D. The bar is polarized and exerts a repulsive force on the balloon. E. Nothing happens because the metal bar is neutral to begin with. + + + 62. Three identical charges Q = 1.0 nC are kept on the corners of an equilateral triangle of side a = 3.0 cm. All charges have a mass of 1.0 g. One of the charges is released while the other two are still kept fixed in the their positions. What is the speed of the released charge when it is very far from the other two? A. 2.0 cm/s B. 3.5 cm/s C. 8.5 cm/s D. 10 cm/s E. 12 cm/s 63. A hose (diameter 2.0 cm) is used to empty a container of water as shown in the figure. The container is a cylinder of radius 3.0 m. What is the speed of the water flow at the end of the hose (point A) when the height of water in the container is 3.0 m? A. 4.4 m/s B. 6.3 m/s A C. 7.7 m/s D. 8.9 m/s 3.0 m 1.0 m E. 9.8 m/s 1.0 m 64. An insulating sphere with a uniformly distributed charge Q > 0 has a radius a. A concentric metallic shell has a charge 2Q and radii b and c. Let V(r) be the electric potential at distance r from the center. Which of the following is true? A. B. C. D. E. V(a) = V(b) = V(c) V(a) > V(b) = V(c) V(a) > V(b) > V(c) V(a) < V(b) = V(c) V(a) < V(b) < V(c) 2Q a Q c b 65. Two spherical capacitors are connected as shown below. Both capacitors have the same geometry, but the capacitor on the right has a dielectric with = 2 between the spherical shells. The capacitor on the left has a charge QL = 2.0 C. What is the charge on the capacitor of the right? Battery A. 1.0 C + B. 2.0 C C. 3.0 C D. 4.0 C E. 8.0 C 66. A non-standard sized microwave oven is 20.0 cm wide. When in use, it supports a standing wave with five anti-nodal planes of the electric field along its width. What is the frequency of the microwaves? A. 1.50 109 Hz B. 2.30 109 Hz C. 3.75 109 Hz D. 7.50 109 Hz E. 9.15 109 Hz 67. A converging lens is shown in the sketch below. The two radii of curvature have absolute values of 0.25 m and 0.45 m. What index of refraction should the glass have if the lens has to have a focal length of 2.00 m? A. 0.72 B. 1.28 0.45 m C. 1.66 D. 2.12 E. 2.50 0.25 m 68. An object is 15.0 cm from the center of a silvered (mirror-like), spherical glass holiday ornament that is 4.00 cm in diameter. What are the position (s') and magnification (m) of its image? A. s' = -1.4 cm and m = 0.066 B. s' = -1.4 cm and m = -0.066 C. s' = -0.93 cm and m = 0.071 D. s' = -0.93 cm and m = -0.071 E. s' = -0.56 cm and m = 0.043 69. The first two diagrams below involve lenses and the second two involve mirrors. The dashed, horizontal line in each figure is the optical axis of the system and horizontal rays are parallel to this axis. Which of the following ray diagrams (if any) is NOT correct? A. B. C. D. E. All four diagrams are correct 70. An infinite array of wires parallel to the z axis is used to a make an
infinite sheet parallel to the yz plane. There are 800 wires per meter. A current of 7.0 A flows through each wire in the positive z direction. Find the magnitude of the magnetic field at a point on the x axis with x = 2.0 m. y A. 1.0 mT B. 2.0 mT C. 3.5 mT D. 4.5 mT E. 7.0 mT 71. A thick copper cable with a 5.00 cm radius carries a 2000 A current uniformly distributed throughout its cross section. What is the magnitude of the magnetic field inside of the wire a distance of 2.00 cm from the center? A. 3.2 mT B. 4.0 mT C. 6.4 mT D. 8.0 mT E. 9.6 mT x 72. A square planar coil of wire has a cross sectional area of 10 cm 10 cm and consists of 100 loops of wire. It is rotated about an axis that is perpendicular to a uniform magnetic field of 1.0 T. At what frequency does it need to spin so as to generate an emf with an amplitude of 100 V? A. 100 Hz B B. 50 Hz C. 33 Hz D. 16 Hz E. 8.0 Hz 73. Take a single loop circuit that consists of a real battery with emf = 20.0 V and an internal resistance of 5.00 , and two resistors, R1 = 3.00 and R2. For what value of R2 will the most power be dissipated in R2? A. 7.00 B. 8.00 C. 10.0 D. 17.0 E. 20.0 74. Which of the following circuits can be used as a low-pass filter, i.e. used to filter out high frequency components of the input signal, Vin: A B C D E. They all are good low pass filters. 75. The whole circuit below is in a region of uniform magnetic field pointing across the page toward the right. The switch is initially open and is suddenly closed. Consider the length of wire that connects the resistor and the capacitor. In which direction does the force on this wire point? A. To the left. B. To the right. C. Out of the page. D. Into the page. E. There will be no force on the wire due to the magnetic field. 76. A diffraction grating has slits that are separated by 0.007 mm. There are 1200 such slits in the grating. If the grating is fully illuminated by a laser beam ( = 600 nm), what is the approximate width of the central spot on a screen located 2.00 m from the grating? A. 1.2 10-6 m B. 2.8 10-6 m C. 1.2 10-5 m D. 2.8 10-4 m E. 1.2 10-3 m 77. An object is placed 20.0 cm from a screen. A converging lens with a 4.00 cm focal length is placed between object and screen. How far from the screen should the lens be placed so as to (i) obtain an image on the screen with (ii) the largest magnitude of magnification? A. 5.53 cm from screen B. 8.71 cm from screen C. 11.3 cm from screen D. 14.5 cm from screen E. 17.2 cm from screen The next four questions are the laboratory final exam. 78. A DC voltage source, three bulbs and a digital voltmeter are
connected as shown below. DC source Bulb 1 Bulb 2 Bulb 3 With these connections, the voltmeter measures the voltage across: A. Bulb 1 B. Bulb 2 C. Bulb 3 D. The combination of bulbs 1 and 2 E. The combination of all three bulbs. 79. In the Electron Beam In A Magnetic Field experiment, electrons are ejected from a hot filament and accelerated through a voltage V. The electrons then enter the region between a pair of Helmholtz coils, which produce a uniform magnetic field when a current I runs through the coils. In the presence of this magnetic field, the electrons follow a circular trajectory. If we double the accelerating voltage, the radius of the electron path is expected to change by a factor of: A. 0.50 B. 0.71 C. 1 D. 1.4 E. 2.0 Insulating handle 80. Which of the following is true about the proper way to charge the disk of an electrophorus? Metal disk Insulating plate A. All the charge is transferred from the insulating plate to the disk. B. The insulating plate always carries negative charge. C. Touching the metal disk to the insulating plate is called grounding. D. The metal disk becomes charged when it is grounded. E. The insulating plate must be recharged by rubbing it every time the disk is charged. 81. A certain potential difference V measured by an oscilloscope is expected to show an exponential decay " "% ! !" " =! !#"$%& $ ! ' # !& where is the time constant of the decay. Shown below is the printout of the oscilloscope and the scales used. Vertical scale : 3 V/major division Horizontal scale : 20 ms/major division Vertical position: V = 0 at bottom of screen. What is the value of the time constant? A. B. C. D. E. 20 ms 48 ms 92 ms 115 ms 160 ms ...
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