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Exercise 23.29 Description: A uniform electric field has magnitude E and is directed in the negative x direction. The potential difference between point a (at x= x_a) and point b (at x= x_b) is V. (a) Which point, a or b, is at the higher potential? (b) Calculate the... A uniform electric field has magnitude E and is directed in the negative x direction. The potential difference between point a (at x = 0.70 m ) and point b (at x = 0.95 m ) is 260 V . Part A Which point, a or b, is at the higher potential? ANSWER: a b Part B Calculate the value of E. Express your answer using two significant figures. ANSWER: E = = 1000 N/C Part C A negative point charge q = −0.200 µC is moved from b to a. Calculate the work done on the point charge by the electric field. Express your answer using two significant figures. ANSWER: W = = −5.2×10 −5 J Electric Fields and Equipotential Surfaces Description: Find the work done to move a unit charge from and to given points on a diagram showing equipotential surfaces, and compare the magnitude of the electric field at these points. The dashed lines in the diagram represent cross sections of equipotential surfaces drawn in 1 V increments. Part A W AB C
What is the work W AB done by the electric force to move a 1 C charge from A to B? Express your answer in joules. Hint 1. Find the potential difference between A and B What is the potential difference V A − V B between point A and point B? Express your answer in volts. Hint 1. Equipotential surfaces Recall that an equipotential surface is a surface on which the electric potential is the same at every point. ANSWER: V A − V B = 0 V Hint 2. Potential difference and work Recall that the potential difference (in volts) between a point a and a point b equals the work (in joules) done by the electric force to move a 1 C charge from a to b. ANSWER: W AB = 0 J Part B What is the work W AD done by the electric force to move a 1 C charge from A to D? Express your answer in joules. Hint 1. Find the potential difference between A and D What is the potential difference V D − V A between point A and point D? Express your answer in volts. ANSWER: V D − V A = -1 V Hint 2. Potential difference and work Recall that the electric potential energy difference between any two points is equal to the negative of the work done by the electric force as a charged object moves between those two points. If we combine this <strong>with</strong> the relationship between electric potential energy and electric potential we have: W AD, by electric force = −∆V AD Q ANSWER: W AD = 1 J Part C The magnitude of the electric field at point C is Hint 1. Electric field and equipotential surfaces Since the diagram shows equal potential differences between adjacent surfaces, equal amounts of work are done to move a particular charge from one surface to the next adjacent one. It follows then that if the equipotentials are closer together, the electric force does the same amount of work in a smaller displacement than if the equipotentials were farther apart. Therefore, the electric force, as well as the corresponding electric
Page 1 and 2: Signed in as Jolie Cizewski , Instr
Page 3: Part A Three equal point charges, e
Page 7 and 8: K = = 5.219×10 −21 J Part B How
Page 9 and 10: Part A Find the potential at the po

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