115Aex2win08verAsol

115Aex2win08verAsol - Name _ last first Student ID Number _...

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Name ___________________________________ Student ID Number ____________ last first I. Point Charges. Two point charges are fixed in place at points O and R as shown. The magnitude of Q = 4 . 00 μ C. The points labeled P and S are just locations (no charge). There are no other electrically charged objects nearby, and the dotted lines indicate horizontal and vertical directions. S × O -Q P R +2Q 50 . 0 cm 25 . 0 cm 25 . 0 cm Ignore gravity in this problem. 1. (3 pts) Which choice best represents the direction of the electric force exerted on the charge at O by the charge at R? A B C D E 2. (5 pts) Which choice best represents the magnitude of this force? 4 . 6 N 2 . 2 x 10 -1 N 1 . 2 N 5 . 9 x 10 -1 N 2 . 9 x 10 5 N A B C D E Now a third charge of value +Q/2 is brought in from a long distance and fixed in place at point S . 3. (5 pts) Which choice best represents the total electric potential energy of these three charges? -9 . 7 x 10 4 J +9 . 7 x 10 -2 J -0 . 65 J +0 . 65 J -0 . 39 J A B C D E Physics 115A, Winter 2008, Version A Exam 2, page 1

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Name ___________________________________ Student ID Number ____________ last first S +Q/2 × O -Q P R +2Q 50 . 0 cm 25 . 0 cm 25 . 0 cm I. continued: The figure shows the situation with all three charges fixed in place. Recall that Q = 4 . 00 μ C. 4. (5 pts) Which choice best represents the magnitude of total electric field strength E at point P due to the three charges? 1 . 72 x 10 6 N/C 1 . 78 x 10 6 N/C 1 . 75 x 10 6 N/C 3 . 07 x 10 12 N/C 1 . 32 x 10 3 N/C A B C D E Use vector components 5. (5 pts) Which choice best represents the electric potential at point P due to the three charges? Assume that the electric potential is zero at an infinite distance from point O. 1 . 12 × 10 5 V 1 . 44 × 10 5 V 1 . 69 × 10 5 V 1 . 76 × 10 5 V 1 . 80 × 10 5 V A B C D E Potential is not a vector. Physics 115A, Winter 2008, Version A Exam 2, page 2
Name ___________________________________ Student ID Number ____________ last first P 10 20 30 40 (cm) (cm) 20 10 R S W II. B. Uniform Electric Field. A uniform electric field of strength E is shown in the figure

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This note was uploaded on 04/07/2008 for the course PHYS 115 taught by Professor Pedigo during the Winter '08 term at University of Washington.

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115Aex2win08verAsol - Name _ last first Student ID Number _...

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