practice_mt2(1)

practice_mt2(1) - PHYSICS 112 FIRST LIIDTE'RM EXAM 9 AM...

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Unformatted text preview: PHYSICS 112 FIRST LIIDTE'RM EXAM - April 22, 1992 9 AM Scfion me. Pelz . I 6 _ .Make sure to put your name and your recitation instructor's name on each page of the exam. This is a closed book exam: calculators are allowed, but no formula sheet. The exam has three parts: . (A) Questions based on the tabs. (3) 10 multiple choice qtiestions. (C) Two “show work” problems. For these, you must show all work and intermediate steps in order to receive full credit. It is suggested that you include simple diagrams to clarify to the grader what you are trying to do. Usefill Constants: K = 8.99 x 10’ Nt'n’fc2 as, = 8.85 x 10‘” C’I'N'tn1 c = 1.61:10'” C 3 = 9.8 m/s’. Nun: ' Rec. Instructor 9 1m. Suction - me. Pclz ‘PAIEI‘A: LAB QUESTIONS (6 points). Write the 1am for the has: answcr in the space The 5311:: show: the scrum of an oscilloscope when it is correctly oonncctcd 1.9 a signal gmcrator. l. 31:: physical quantity mcasurcd on the Mal axis is (3) mt (b) electric field (6) potential energy (d) voltage diffmcc '(c) film: 2. The physical quantity mcasurcd on the hpfimml axis is (a) currcm (b) dccuic ficld (c) potcnfial mm (d) voltage difi'cxmcc (c) 15111: Nine 3 Rec. Instructor .9131. Section -Prof. Pei: same: 1. ___._( mm CHOICE. Write the letter for the best answer in the space provided. Questions are worth 5 points «ch. An electric hater is plugged into a 120 V outlet and produces 1000 W_cf heat. How much current does the heater draw? answer) (a) 8.3 A (b) 0.12 A . (c) 14.4 A (d) 4.2 A (e) 10 A A charge q = ~3gC is placed at a certain point in an electric field and experiences an electric fore: F = 0.04 N pointing to the left. The electric field E at this point is. (answer) . (107.5 x 10"5 NIC, pointing up. —— (b) 7.5 x 10" MC, pointing to the right. (c) 7.5 x 10" NIC, pointing to the left. (d) 1.3 x 10‘ N/C, pointing to the left. (e) 1.3 x 10‘ we, pointing to the right. A solid metal sphere is placed into a strong electric field. In the static situation, which of the following is Em (answer) (a) The electric field is zero inside the Sphere. (b) The electric potential is constant throughout the sphere. (c) positive and negative charge exactly balance at m point on the sphere. (d) The electric field is perpendicular to the surface just outside the sphere. (c) There is no moving charge inside the sphere. A parallel—plate capacitor with an air-gap is connected to a battery and has a certain charge Q as shown in the figure. How would the charge change if the air-gap is filled with quartz? (Assume that the dielectric constant for quartz is K = 4.0) (answer) (a) Q would become 16 times as large. (b) Q would become 4 times as large. (c) Q would not change. (d) Q would become U4 as large. (el 0 would become. 1’16 aslartgt, Name Ree. Instructor .9 am. Section - Prof. Pelz (a) 0.75 N/C. pointing towards the charge. (b) 3 WC, pointing away from the charge. (c) 6 NIC, pointing away from the charge. (:1) 6 NC, pointing towards the charge. (e) 9 MC, pointing towards the charge. ' 3. TWO conducting parallel plates are connected to a 60 V battery as shown in the figure. The area of each plate is 0.2 m’ and they are separated by an air-gap d = 3 cm. The electric field E between the plates is: ' ' A B __ (answcr) ' (a) 2000 ‘Wrn, pointing from plate A to B. (b) 2000 Wm, pointing from plate B to A. (c) 500 Wm, pointing from A to B. (d) 500 Wm, pointing from B to A. (1:) none of the above. S Rec. Instructor Name _ 9 3.11:. Section - Prof. Pelt The next two questions refer to the diagram shown below. Fons light bulbs, each with the same resistance are oonnectod together as shown. Initially. all four bulbs are glowing and the switch S is m 9. Ifbulb B is removed from the circuit, then what happens to the current through bulb A and through bulb D? ' (answer) (a) A increases, D decreases. (b) A increases, D stays the same. (e) A de‘ereasos, D increases 0:!) A decreases, D stays the same. (e) A decreases, D decreases. 10. Ifnow the switch S is 9192919 what happens to the current through bulbs A and D? _.__-. (answer) . (a) A increases, D decreases. (b) A increases, D stays the someo- (c) A 6m, D increases. (d) A decreases, D stays the same. (e) A decreases, D decreases 6 Name Ree. Instmeto: P 3.111. Section - Prof. Pei: - 2m C: Pmblems. You must show all work and an intennediate steps to receive full cram ' Sketches or diagrams an: often useful. - ProblemI. PointehargesQ, é-SflcmdQ= +53szphced0Amapartasshowninthefigure. (a) A certain point P is located 0.3 m above charge Q as shown.' Draw a diagram indicating the directions of the eiectfic field vector: due to each of the two charges. (5 pts.) Q.i9‘_°‘“""—"@ 0:. (b) Calculate both the x- and 3- components of the total electric field vector at point P. (10 - ~ pts.) (c) Calculate the electric potential V, at point P. (Assume that the potential at infinite distance is equal to zero) (5 pts.) (:51) Calculate the change in potential m APE of the system if a third charge q; = -2 ,u-C is brought from an infinite distance and placed at point P. 7 Name Rec. Instsuctor 9 an. Section - Prof. Pelz _1’mblem11. mmmnare,eonnectedtoabatteryasshown,whetem=100,11; =50, ’=1onandv=4ov. L. R: a a b a. _ (It) Find the equivalent resistance of this network. (10 pts.) (b) How much current passes through the battery? (5 pts.) (c) Find the voltage difference V“ between the points 13 and e shown in the figure. (5 pts.) (d) Evaluate the current 32 which passes through resistor R2. (5 pts.) ANSWERS TO SOME OF THE SAMPLE PHYSICS 112 MIDTERMS (Note: * means that the material is not included on midterm this quarter) I. PELZ: April 22, 1992 Part A. *1. D *2. E Part B 1. A 2. E 3. C 4. B (if battery remains connected) 5. 12 N/C and points towards the point charge 6. D 7. A 8° B 9. D 10. B PartC a) E 5' I a) i b) Ex = — 1.4 x 10 N/C " ““fix Ey=~3.9x105’N/C C) —6.0 X 10 V _ d} 0.12 J II a) 13.33.. b) 3.0A c} 10 V d) 2.0 A ...
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practice_mt2(1) - PHYSICS 112 FIRST LIIDTE'RM EXAM 9 AM...

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