# ch19 - chapter ELECTRIC POTENTIAL ENERGY AND THE ELECTRIC...

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chapter ELECTRIC POTENTIAL ENERGY AND THE ELECTRIC POTENTIAL Section 19.1 Potential Energy Section 19.2 The Electric Potential Difference 1. Which one of the following statements is true concerning the work done by an external force in moving an electron at constant speed between two points in an electrostatic field? (a) The work done is always zero joules. (b) The work done is always positive. (c) The work done is always negative. (d) The work done depends on the total distance covered. (e) The work done depends only on the displacement of the electron. 2. Complete the following statement: The electron volt is a unit of (a) energy. (c) electric charge. (e) electric power. (b) electric field strength. (d) electric potential difference. . 3. Which one of the following statements best explains why it is possible to define an electrostatic potential in a region of space that contains an electrostatic field ? (a) Work must be done to bring two positive charges closer together. (b) Like charges repel one another and unlike charges attract one another. (c) A positive charge will gain kinetic energy as it approaches a negative charge. (d) The work required to bring two charges together is independent of the path taken. (e) A negative charge will gain kinetic energy as it moves away from another negative charge. . 4. The electric potential at a certain point is space is 12 V. What is the electric potential energy of a –3.0 μ C charge placed at that point? (a) +4 μ J (c) +36 μ J (e) zero µJ (b) –4 μ J (d) –36 μ J 5. A completely ionized beryllium atom (net charge = +4 e ) is accelerated through a potential difference of 6.0 V. What is the increase in kinetic energy of the atom? (a) zero eV (c) 4.0 eV (e) 24 eV (b) 0.67 eV (d) 6.0 eV . 6. Two positive point charges are separated by a distance R . If the distance between the charges is reduced to R /2, what happens to the total electric potential energy of the system? (a) It is doubled. (d) It is reduced to one-half of its original value. (b) It remains the same. (e) It is reduced to one-fourth of its original value. (c) It increases by a factor of 4. . 8. A proton moves in a constant electric field E from point A to point B. The magnitude of the electric field is 4.2 × 10 4 N/C; and it is directed as shown in the drawing, the direction opposite to the motion of the proton. If the distance from point A to point B is 0.18 m, what is the change in the proton’s electric potential energy, EPEA – EPEB? (a) +2.4 × 10 –15 J (c) +1.2 × 10 –15 J (e) –1.8 × 10 –15 J (b) –1.2 × 10 –15 J (d) –2.4 × 10 –15 J Section 19.3 The Electric Potential Difference Created by Point Charges E A B proton 0 1.0 m x –5.0 μC +2.0 μC

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186 Chapter 19 Electric Potential Energy and the Electric Potential 9. Two point charges are arranged along the x axis as shown in the figure. At which of the following values of x is the electric potential equal to zero? Note
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ch19 - chapter ELECTRIC POTENTIAL ENERGY AND THE ELECTRIC...

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