115Bex2win08verCsol

# 115Bex2win08verCsol - 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 = 3 . 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 × × 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? 3 . 4 N 4 . 1 x 10 -1 N 1 . 2 N 5 . 9 x 10 -1 N 1 . 0 N A B C D E Now a third charge of value +1 . 5Q 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? +0 . 62 J -0 . 62 J -0 . 53 J +0 . 53 J -1 . 01 J A B C D E ERROR: above numbers are fixed to remove error. The old numbers were: +1.0 J -1.0 J -0.85 J +0.85 J -0.43 J O +Q P R -2Q 40 cm 40 cm 40 cm Physics 115B, Winter 2008, Version C Exam 2, page 1

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Name ___________________________________ Student ID Number ____________ last first S +1.5 Q × O +Q P R -2Q 40 cm 40 cm 40 cm I. continued: The figure shows the situation with all three charges fixed in place. Recall that Q = 3 . 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? 4 . 92 x 10 -1 N/C 1 . 78 x 10 5 N/C 1 . 69 x 10 5 N/C 6 . 32 x 10 4 N/C 1 . 64 x 10 5 N/C A B C D E ERROR: above numbers are fixed to remove error. The old numbers were: 4 . 05 x 10 -1 N/C 1 . 78 x 10 5 N/C 4 . 00 x 10 5 N/C 6 . 32 x 10 4 N/C 1 . 35 x 10 5 N/C 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. 2 . 14 × 10 5 V 2 . 26 × 10 4 V 1 . 58 × 10 5 V 1 . 75 × 10 5 V 1 . 82 × 10 5 V A B C D E Potential is not a vector Physics 115B, Winter 2008, Version C Exam 2, page 2
Name ___________________________________ Student ID Number ____________ last first P 10 20 30 40 (cm) (cm) 20 10 R S W II. Uniform Electric Field. A uniform electric field of strength E is shown in the figure to the right. The source charges that create this

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## This test prep 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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115Bex2win08verCsol - Name _ last first Student ID Number _...

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