2007B_phys208_Exam4A_solutions
6 Pages

2007B_phys208_Exam4A_solutions

Course Number: PHYS 208, Fall 2008

College/University: Texas A&M

Word Count: 615

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Version A - Page 9 Problem 1 (20 points): A small plastic ball (mass m = 1.5 g) is tied to a very light 2.00 cm string that is attached to the ceiling. See the figure. A uniform horizontal electric field exists between two plates. When the ball has been given an excess charge of q = 147 C, you observe that it remains suspended, with the string making an angle of = 30.0o with the vertical. Find the magnitude and...

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A Version - Page 9 Problem 1 (20 points): A small plastic ball (mass m = 1.5 g) is tied to a very light 2.00 cm string that is attached to the ceiling. See the figure. A uniform horizontal electric field exists between two plates. When the ball has been given an excess charge of q = 147 C, you observe that it remains suspended, with the string making an angle of = 30.0o with the vertical. Find the magnitude and direction of electric field. Version A - Page 10 Problem 2 (20 points): Your assignment in a PHYS 208 lab is to characterize the motion of a rectangular circuit shown in the figure. The rectangular loop is hinged along the y axis. It carries a 15.0 A current and is located in a uniform 1.20 T magnetic field oriented in the +x direction. (a) (10 pts) Make a clear sketch showing the direction of the force that the magnetic field exerts on each segment of the circuit. (b) (10 pts) Of four forces you drew in part (a), decide which one(s) exerts a torque about the hinge. Then calculate the magnitude of only the force(s) that exerts this torque. (1) (2) (3) (4) 2 pts 2 pts 4 pts 2 pts Version A - Page 11 Problem 3 (20 points): In a PHYS 202 lab, you are assigned to calculate the time response of the circuit ( = 100 V, R1 = 10 , R2 = 30 , and L = 2.0 H) before its measurements. See the figure. Find (a) (10 pts) the current through each of the resistor just after the switch (S) is closed; (b) (5 pts) the current through each resistor after S has been closed a long time; (c) (5 ps) the current through R1 right after S is re-opened in part (b). Version A - Page 12 Problem 4 (20 points): You are a chief engineer. General Electric at Texas Corp (GET Corp.) just hires Dr. Kamon as a chief His engineer. first task is to evaluate your design of metal detector. You explain using the figure: In its simplest form, a metal detector consists of an oscillator producing a varying current I0(t) that passes through a coil r (transmitting coil) producing a varying magnetic field B0 to the right. If an electrically-conductive metal plate is close to the coil, eddy currents will be r induced in the metal, and this produces an varying magnetic field B of its r own to the right. If another coil (receiver coil) is used to measure B , the r change in B will be detected as a varying current I in the receiver coil. He asks: (a) (5 pts) What is the principal physics behind this technology? (b) (5 pts) Sketch the direction of the eddy current on the metal plate, r assuming the direction of B in the figure is correct. (c) (10 pts) Is I0(t) increasing or decreasing to observe I as in the figure? Or both? Why? Version A - Page 13 Problem 5 (10 points): EM Wave A small helium-neon laser emits red visible light with a power of P = 3.20 mW in a beam that has a diameter of D = 2.50 mm. Take the speed of light in air to be c = 3.00 108 m/s . What is the total energy contained in a 1.00-m length of the beam? Version A - Page 14 Problem 6 (10 points): Lost and Found You are shining the light into a pool (depth d) and see a key, which is lying on the bottom of the pool. The index of refraction for water is n. (a) (6 pts) Express X in terms of h, d, L and n. (Hint: X = 4.4 m for h = 1.2 m, d = 4.0 m, L = 1.5 m, n = 1.33) (b) (2 pts) Find X for n 1 . Sketch the path of the light. (c) (2 pts) Find X for n . Sketch the path of the light. ALSO: okay with 1 L sin tan h X = L + d tan n

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Texas A&M - PHYS - 208
dTOTAL Letter Method 1 Method 2 as in using syllabus Best2 (750) (750) Grade A 95.7 96.7 A 90.3 91.9 A 90.1 91.1 A 86.0 88.1 B 76.3 81.8 B 78.4 80.9 B 77.8 80.2 B 76.2 79.2 B 77.3 79.1 B 75.4 79.0 B 75.5 78.4 B 75.1 78.4 B 74.0 78.0 B 74.8 77.8 B 7
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
ID1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57Midtem (MT) Grade Summary Old Lab Exam 1(%) Exam 2(%) Exam 3(%) MT Total(%) (195) (
Texas A&M - PHYS - 208
Version A - Page 1 of 8Version A - Page 2 of 8Problem 1 Problem 2 Problem 3 Problem 4 Problem 5 Problem 6 TOTAL(20) (20) (20) (20) (10) (10) (100)Version A - Page 3 of 8 Problem 1 (20 points): Mickey Mouse? No. It is a water molecule which ha
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
11-Jul19-Jul22-Jul24-Jul Exam 2 (max = 185) 161 169 159 170 139 166 145 128 124 152 151 118 156 146 143 138 147 139 109 134 115 114 121 136 109 149 104 132 118 143 140 97 121 120 124 134 81 105 99 105 133 164Temp. ID 1 2 3 4 5 6 7 8 9 10 11 1
Texas A&M - PHYS - 208
Version A - Page 1 of 8Version A - Page 2 of 8Problem 1 Problem 2 Problem 3 Problem 4 Problem 5 TOTAL(25) (25) (15) (25) (10) (100)Version A - Page 3 of 8 Problem 1 (25 points): Invention! You are inspired by a PHYS 208 lecture to design an e
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
Problem 1 (25 points) - SolutionsProblem 2 (25 points) - SolutionsThe long, straight wire AB shown in the figure carries a current of I1 = 14.0 A. The rectangular loop whose long edges are parallel to the wire carries a current of I2 = 5.00 A. (a)
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
Physics 208 Electricity, Magnetism, and Light Sects.301-305 Summer 2007 Prerequisites: 1 semester of Calculus (MATH 151) and 1 semester of Mechanics (PHYS 218). Concurrent registration in 2nd semester of Calculus (MATH 152) is formally permitted. H
Texas A&M - PHYS - 208
Exam 1 raw score X (max = 195)HW's for Exam 1No pick-up (6/18)HW7 (23-?)HW4 (21-94)HW3 (21-75)HW5 (22-36)HW6 (23-63)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 4
Texas A&M - PHYS - 208
14 12Number of StudentsPHYS-208 Exam 3 (Summer 2007) N=72 (7/25/2007)F D C B A10 8 6 4 2 072.980900 1001020[Raw Score + Bonus] (%)3040506070
Texas A&M - PHYS - 208
14 12Number of StudentsPHYS-208 Final Exam (Summer 2006) N=73 (8/08/2006)F D C B A50.210 8 6 4 2 080 90 0 10 0 10 20 30Raw Score (%)40506070
Texas A&M - PHYS - 208
16 14Number of StudentsPHYS-208 Exam 1 (Summer 2006) N=81 (6/16/2006)F D C 65.5 B A12 10 8 6 4 2 080 90 0 10 0 10 20 30 40 50 60 70Raw Score (%)
Texas A&M - PHYS - 208
16 14Number of StudentsPHYS-208 Exam 2 (Summer 2006) N=84 (6/30/2006)F D C B A12 10 8 6 4 2 059.680900 100102030Raw Score (%)40506070
Texas A&M - PHYS - 208
Texas A&M - PHYS - 208
16 14Number of StudentsPHYS-208 Overall (Summer 2007) N=72 (8/09/2007)F D C B A12 10 8 6 4 2 080 90 0 10 0 10 20 30 40 50 60 7067.2[Raw Score + Bonus] (%)
Texas A&M - PHYS - 208
16 14Number of StudentsPHYS-208 Final Grade (Summer 2006) N=76 (8/08/2006)F D C B A12 10 8 6 4 2 080 90 0 10 0 10 20 30 40 50 60 7070.4Raw Score (%)
Texas A&M - PHYS - 208
Texas A&M - PHYS - 218
Texas A&M - PHYS - 218
Texas A&M - PHYS - 218
Texas A&M - PHYS - 218
Texas A&M - PHYS - 218
Texas A&M - PHYS - 218
Texas A&M - PHYS - 218
Texas A&M - PHYS - 218