HW 03 Due: 11:00pm on Friday, February 18, 2011 Note:To understand how points are awarded, read your instructor's Grading Policy. [Switch to Standard Assignment View] Moving a ChargePart A A point charge with charge = 3.50 is held stationary at the origin. A second point charge with charge = -4.10 moves from the point ( 0.165 , 0) to the point ( 0.265 , 0.260 ). How much work is done by the electric force on the moving point charge? Hint A.1 How to approach the problem Hint not displayedHint A.2 Calculate the initial electric potential energy Hint not displayed Hint A.3 Calculate the final electric potential energy Hint not displayed Express your answer in joules. Use = 8.99×109for Coulomb's constant: . ANSWER: = -0.434CorrectElectric Potential, Potential Energy, and ForceLearning Goal: To review relationships among electric potential, electric potential energy, and force on a test charge This problem is a review of the relationship between an electric field , its associated electric potential , the electric potential energy , and the direction of force on a test charge.
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Part A Electric field lines always begin at _______ charges (or at infinity) and end at _______ charges (or at infinity). One could also say that the lines we use to represent an electric field indicate the direction in which a _______ test charge would initially move when released from rest. Which of the following fills in the three missing words correctly? ANSWER: (positive; negative; negative) (positive; negative; positive) (negative; positive; negative) (negative; positive; positive) CorrectNote that the electric field vector is everywhere tangent to the electric field lines. Like electric field lines, the electric field vector generally points away from positive charges and toward negative charges. Part B Would a positive test charge released from rest move toward a region of higher or lower electric potential (compared to the electric potential at the point where it is released)? Hint B.1 Potential, field, and force Hint not displayedANSWER: higher electric potential lower electric potential CorrectPart C Now imagine that the sign of our test particle is changed from positive to negative, but the electric potential remains the same. Which of the following statements is correct?