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Electrical Energy and Current

Problem A

1. What is the potential difference between a point 0.48 mm from a charge of
2.9 nC and a point at infinity?

2. The potential energy of an electron (q = -1.6 ´ 10-19 C) increases by
3.3 ´ 10-15 J when it moves 3.5 cm parallel to a uniform electric field. What is the magnitude of the electric field through which the electron passes?

3. A charged particle gains 3.1 ´ 10-12 J of potential energy when it moves
4.7 cm through a uniform electric field. The potential difference across this distance is -73 V.

a. What is the magnitude of the electric field?

b. What is the magnitude of the charge on the particle?

4. A charged particle moves through a distance of 9.35 m parallel to a uniform electric field. The electrical potential energy of the particle increases by
3.17 ´ 10-10 J as it moves. The electric field has a magnitude of
1.25 ´ 105 N/C.

a. What is the charge on the particle?

b. What is the potential difference between the starting and final positions?

5. There is an electric field close to the surface of Earth. This field points toward the surface and has a magnitude of about 1.5 ´ 102 N/C. A charge moves perpendicularly toward the surface of Earth through a distance of 439 m, the height of the Sears Tower in Chicago, Illinois. During this trip, the electric potential energy of the charge decreases by 3.7 ´ 10-8 J.

a. What is the charge on the moving particle?

b. What is the potential difference between the top of the Sears Tower and the ground?

c. What is the electric potential of the charge at its final position?

6. Two parallel plates are separated by a distance of 0.077 cm. Between the plates is a uniform electric field having a magnitude of 6.5 ´ 102 N/C. What is the magnitude of the potential difference between the plates?

7. A proton (q = 1.6 ´ 10-19 C) moves 3.75 m in the direction of a uniform electric field having a field strength of 383 N/C.

a. What is the magnitude of the potential difference between the initial and final positions of the proton?

b. What is the change in the electrical potential energy of the proton?

8. A charged oil droplet gains 1.9 × 10-19 J of electrical potential energy while moving 3.0 cm in a uniform electric field. What is the charge on the droplet if the strength of the electric field is 2.0 × 104 N/C?

9. The Eiffel Tower has a height of 0.30 km. Suppose the atmospheric electric field of the Earth at the Eiffel Tower is 95 N/C directed downward. What is the electric potential difference between the ground and the tip of the Eiffel Tower?

10. Cars start by generating a 3.0 × 106 N/C electric field that causes a spark to cross a gap in a spark plug. The gap of a standard spark plug is 6.25 × 10-4 m. What minimum potential difference must be applied across a standard spark plug to start the car?

11. Two charged plates separated by 15 cm create a uniform electric field of 360 N/C. What is the potential difference between the plates?

12. An electron (q = −1.6 × 10-19 C) has an electrical potential energy of 1.1 × 10-18 J in an electric field. What is the electric potential at that point in the field?

13. What is the electric potential at a point where an alpha particle (q = 3.2 × 10-19 C) has an electrical potential energy of 3.5 × 10−17 J?

14. Two charged plates separated by 4.0 cm create a uniform electric field of 3.0 × 102 N/C. The electric potential at one of the plates is 6.0 V. What is the electric potential at the other plate?

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Holt Physics 139 Problem Workbook