PHYSICS 202 FINAL EXAM Wednesday, May 12, 2004, 8-10 am SECTION:

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1 PHYSICS 202 FINAL EXAM Wednesday, May 12, 2004, 8-10 am NAME: SECTION: Note: 517 Recitation Mon 4: Recitation Wed 10: Recitation Wed 8: Recitation Mon 1:50 There are a total of 18 problems on this test. For each problem, write your answer in the space provided. You may use the backs of the pages for scratch calculations if you wish, but only the work in the spaces provided on the front of the pages will be graded. Problems A1-A8 are worth 3 points each. Problem A9 is worth 4 points. For these nine problems, you do not need to show calculations or explain your reasoning. Also, no partial credit will be awarded for incorrect answers. Problems B1-B9 are worth 8 points each. For these nine problems, you must show your work and/or explain your reasoning to receive any credit for a problem merely stating the answer is NOT sufficient. Partial credit will be awarded where appropriate. REMINDER: An answer CAN NOT be completely correct if it has the wrong units! G O O D L U C K!!!!

2 A1: Two heaters are connected to a battery in parallel. One uses 275 W, while the other uses 190 W. If the heaters are rearranged so they are in series, the power provided by the battery: becomes smaller stays the same becomes larger A2: Drawings I and II show two examples of electric field lines. Encircle the letter for each of the following statements that is true: (c) (d) In both I and II the electric field is the same everywhere. As you move from left to right in each case, the electric field becomes stronger. The electric field in I is the same everywhere but becomes stronger in II as you move from left to right. The electric fields in both I and II could be created by positive charges located somewhere to the left and negative charges located somewhere to the right. A3: The figure shows a square, with different positive charges fixed at two of the corners. A third charge that is negative is brought to one of the empty corners. The electric potential energy of the third charge is: positive negative The magnitude of the electric potential energy of the third charge is greater when it is located at corner: A B A4: Suppose you stand in front of a concave spherical mirror. It is possible for your image to be (circle all that are possible): Real and upright Virtual and upright Real and inverted Virtual and inverted A5: In the figure, the magnitude of the magnetic field is decreasing in time. The electric field between the plates of the parallel plate capacitor points: up there is no field down A6: The figure shows two double slits, A and B, and two wavelengths of light, 1 and 2. For which combination will the pattern of bright and dark fringes on an observation screen be least spread out? A-1 A-2 B-1 B-2

3 A7: An electric charge moves vertically downward through a laser beam that is passing from left to right. The electric field in the laser beam is oriented in the horizontal direction. The charge experiences (circle all that are correct): An electric force A magnetic force No force A8: A hydrogen atom is in an excited state. How does its ionization energy compare to the ionization energy when the atom is in its ground state? It s larger It s the same It s smaller A9: (4 points) Two radioactive nuclei A and B have half-lives T 1/2,A and T 1/2,B, where T 1/2,A is greater than T 1/2,B. During the same time period, the fraction of nuclei A that decay is: greater than the same as smaller than the fraction of nuclei B that decay. Section B: Must show your work. Partial credit will be awarded where appropriate. B1: In the figure below, a uniform electric field of 950 N/C passes from left to right. A cube, with sides of length 0.17 m, is oriented so that all the edges are either parallel or perpendicular to the electric field, as shown. Side A of the cube is the left side, side B is the top, and side C is the right side. Find the total electric flux: (c) (d) Passing through the entire cube Passing through side A Passing through side B Passing through side C

4 B2: The drawing shows four point charges. The value of q is 1.7 :C, and the distance d is 0.45 m. Find the total potential at the location P. Potential B3: A series RCL circuit contains a 4.90-:F capacitor and a generator whose voltage is 13.0 V. At a resonant frequency of 1.40 khz, the power dissipated in the circuit is 22.0 W. Find the values of: The inductance The resistance

5 B4: A diffraction grating produces a first-order bright fringe that is m away from the central bright fringe on a flat screen. The separation between the slits of the grating is 4.19 x 10-6 m, and the distance between the grating and the screen is m. What is the wavelength of the light shining on the grating? Wavelength B5: An object is 16 cm in front of a diverging lens that has a focal length of -11 cm. How far in front of the lens should the object be placed so that the size of the image is reduced by a factor of 1.8? Distance

6 B6: Bones of the woolly mammoth have been found in North America. Bones of one animal have a 14 6C activity per gram of carbon that is 18% of what was present in the live animal. How long ago (in years) did this particular animal die? Years B7: A laser emits 1.25 x photons per second in a beam of light that has a diameter of 1.80 mm and a wavelength of nm. Determine the average electric and magnetic field strengths for the electromagnetic wave that constitutes the beam. Electric field strength Magnetic field strength

7 B8: In the figure below, the two wires are parallel and separated by a distance of m. The current in each wire is I = 27 A. By applying an external magnetic field (created by a source other than the wires), it is possible to arrange things so that each wire feels no net force. Determine the direction and magnitude of this external field. Direction (circle your answer): right left into page out of page Magnitude B9: The figure below shows a copper wire bent into a circular shape with a radius of 0.55 m. The radial section BC is fixed in place, while the copper bar AC sweeps around at an angular speed of 0.18 rad/s. The bar makes electrical contact with the wire at all times. The copper wire and bar have negligible resistance. A uniform magnetic field exists everywhere, is perpendicular to the plane of the circle, and has a magnitude of 4.1 x 10-3 T. Find the magnitude of the current induced in the loop ABC. Current