physics final 2 - ‘ S‘semgitcié’ FINAL EXAM PHYSICS...

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Unformatted text preview: ‘ S‘semgitcié’ FINAL EXAM PHYSICS 171.102 This exam is closed book and closed notes (but see the attached “formula sheet”). The maximum number of points for each problem is shown in parentheses. SHOW ALL WORK. Where part of a problem uses the result of an earlier part which you did not answer, the appropriate symbol may be substituted for that result. No partial credit will be given for an answer without supporting work being shown. No credit will be given when multiple answers are given to the same problem (even if one is correct). Answers should be written in pen (not pencil). Cross out mistakes (do not erase). The exam is from 2:00 to 5:00PM. Good luck! 1. (10) Two initially uncharged metal spheres A and B are in contact with one-another. A negatively charged insulator in the shape of a wand is brought close to sphere A without touching it (as shown below). Sphere B is then moved slightly to the right so that it is no. longer in contact with sphere A. Finally, the charged'Wand is removed. What is the resulting net charge on sphere A (+, —, or 0)? What about sphere B? Explain your reasoning. ":03; ..$ A B , . k v E :l .J or) m A B WNW.” 4.3% 2. (15) A positive charge Q is located a distance L/ 2 directly above the center of a flat square surface with dimensions L by L (see below). Calculate the flux of the Electric field due to this charge through the square surface. This can be done very easily using Gauss‘s Law! Explain your reasoning. ; l 5. (15) A conducting ring is placed partially inside a region in which the magnetic field points directly into the page (as shown below). In which direction(s) should you move the conducting ring to genérate a c0unter-cldckwis'e current in it (right, left, up, down, into the page, or out of the page)? Emglaz'n your realigning. . 1“"."5 1‘, 6. (10) The diagram below shows an inductor that is part of a circuit. The current flowing through the inductor is increasing with time, inducitig an EMF in the inductor in the direction indicated. In what direction is the current flowing (to the left or right)? Explain your reasoning. t . Jilin duel-or vamp . --——--—=> ' Ds'rech'on 6F induced EMF 7. (20) A 150 Q resistor is in series with a 0.250 H inductor and a capacitor, with the collection connected to an ac voltage source at 60.0 Hz. What value for the capacitance results in a total impedance of 150 Q?Show your work! UofiH 11. (20) Two radio transmitters broadcast exactly in—phase with one—another at a frequency of 150 MHz (1/ 2: 1.5x 108 3‘1). They are separated from one—another by exactly 17 meters in the East-West direction (see below). The resulting interference pattern is measured at three locations shown below. Location A is exactly halfway between the two transmitters. Location B is exactly 17 meters directly North of location A. Location 0 is exactly 10 meters directly East of transmitter #2. B N firm «4 $1 3 E MA A c S lE ' Hm ——————*—-—-——.‘DM__A a. (5) What is the wavelength (A) of the electromagnetic waves? b. (15) At which location(s) will there be constructive interference between the two transmitters? At which location(s) will there be destructive interference? Explain your reasoning. 12. (20) Many optical instruments like camera lenses use an “anti—reflection coating” on their surfaces. A typical material used for such coating is M gF, which has an index of refraction of 1.38 at a wavelength of 500 nm. If the glass in the lens has a corresponding index of refraction of 1.7 , what is the minimum thickness for the MgF layer that will eliminate reflections in the middle of the visible spectrum (at A = 500 run)? You may assume that the light enters perpendicular to the surface. Show you work! ...
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physics final 2 - ‘ S‘semgitcié’ FINAL EXAM PHYSICS...

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