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# Midterm1Answers - PHYSICS 9C MIDTERM 1 April 23, 2007 I...

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PHYSICS 9C MIDTERM 1 April 23, 2007 I certify by my signature below that I will abide by the UC Davis Code of Academic Conduct. This includes not copying from anyone else’s exam not letting any other student copy from my exam not discussing this exam with any student who has not yet taken it, nor providing any information, written or oral, that might get to a student who has not yet taken it. Anyone suspected of cheating will be automatically reported to Student Judicial Affairs. LAST NAME: FIRST NAME: STUDENT ID: (P R I N T) (P R I N T) (LAST 4 DIGITS) Signature: Problem 1 (two points) Two particles A and B have identical charge Q. For a net force of zero to be exerted on a third charge it must be placed: A. on the line joining A and B, not between the particles B. midway between A and B C. at none of these places (there is no place) D. on the line joining A and B, closer to one of them than the other E. on the perpendicular bisector of the line joining A and B but away from the line Solution: B Problem 2 (two points) A dipole consists of two equal and opposite charges located on the vertical axis, as shown in the figure. The direction of the electric field at point P is A) B) C) D) E) The electric field is zero at point P. a a -Q +Q - + P

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Solution: In those problems where the negative charge is on the top and the positive is on the bottom, the answer is B, while if the positive charge is on the top and negative on the bottom, the answer is D. Problem 3 (two points). An electric dipole is positioned perpendicular to a constant electric field which is directed from the left to the right. The initial dipole orientation is with the negative charge on the top and with positive charge on the bottom. (See figure of previous problem.) The distance between the charges is kept fixed. What happens to the dipole after it is released?
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## This note was uploaded on 04/07/2008 for the course PHY 9C taught by Professor Zieve during the Winter '08 term at UC Davis.

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Midterm1Answers - PHYSICS 9C MIDTERM 1 April 23, 2007 I...

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