The electric potential difference (ΔV) between any two points in space is defined as the change in potential energy per unit positive test charge •

Formulas •

Exercise 6, p. 591 Consider two points at different distances from a positive point charge. (a) The point closer to the charge is at a (1) higher, (2) equal, or (3) lower potential than the point farther away. Why? (b) How much different is the electric potential 20 cm from a charge of 5. 5 µC compared to 40 cm from the same charge? ANSWER: +1. 2 x 105 V

Exercise 14 revisited, p. 592 An electron is moved from point A to point B and then to point C along two legs of an equilateral triangle with sides of length 0. 25 m. (b) What is the potential difference between A and C? ANS: 3. 8 V (c) Which point is at a higher potential? ANS: Point C

Three charges on a line Find the potential at location 1. ANSWER: -6 x 105 V 2 -4. 0μC 0. 2 m 1 0. 15 m 3 -7. 0 μC Find the potential energy of a +3. 0 µC placed at location 1. ANSWER: -1. 8 J

Three charges in a plane Find the potential at location 1. ANSWER: -8. 1 x 105 V 2 -6. 0 μC Find the potential energy of a -4. 0 µC placed at location 1. ANSWER: 3. 24 J 0. 15 m 73 o 1 0. 1 m 3 -5. 0 μC

Exercise 18, p. 592 What is the value of the electric potential at (a) The center of the square ANSWER: -1. 3 x 106 V (b) A point midway between q 1 and q 4? ANSWER: -1. 3 x 106 V