Homework Helpers: Physics

5 Electric Charges, Forces, and Fields

Chapter 5 Examination

Part I—Matching

Match the following terms to the definitions that follow.

a. electroscope

b. induction

c. conduction

d. positive ion

e. negative ion

f. polarization

g. grounding

h. capacitor

i. electric potential

_____1. A device that stores an electric charge.

_____2. The process of charging an object by bringing it near a charged object and providing a pathway for charge between the neutral object and the ground.

______3. An atom that has gained one or more electrons.

______4. The electric potential energy of a charged object, divided by its charge.

______5. Providing a conductive path between a charged object or a circuit to the ground.

Part II—Multiple Choice

For each of the following questions choose the best answer.

6. A neutral atom must have an equal number of

a) protons and electrons

b) protons and neutrons

c) neutrons and electrons

d) protons, neutrons, and electrons

7. An electroscope obtains a charge of –1.44 × 10^–16 C. How many excess electrons does this represent? (e = –1.60 × 10^–19 C)

a) 2.30 × 10^–35 C

b) 1.44 × 10^–16 C

c) 1.2 × 10³ C

d) 9.00 × 10² C

8. A metal sphere with an excess of 17 electrons touches an identical metal sphere with an excess of 5 electrons. After the spheres are separated, how many excess electrons would each sphere have?

a) 5

b) 11

c) 12

d) 22

9. The electrostatic force of attraction between two charged objects is F. What would be the force between the objects if the charge on each of the objects were tripled?

a) 3F

b) –3F

c) 6F

d) 9F

10. The electrostatic force of attraction between two charged objects separated by a distance of 1.0 cm is given by F. If the distance between the objects were increased to 5.0 cm, what would be the electrostatic force of attraction between them?

a) 5F

c) 25F

11. What is the magnitude of the force experienced by an electron in an electric field with an intensity of 3.50 × 10⁵ N/C?

a) 2.19 × 10²⁴ N

b) 5.60 × 10^–14 N

c) 1.9 × 10²² N

d) 4.5 × 10^–14 N

12. Calculate the electric field intensity at a distance of 0.875 m away from a point charge of 1.70 C. (k_c = 9.0 × 10⁹ N × m²/C²).

a) 1.9 N/C

b) 1.7 × 10¹⁰ N/C

c) 2.0 × 10¹⁰ N/C

d) 1.3 × 10⁹ N/C

13. 5.8 × 10^–19 J of work are done by a uniform electric field with a strength of 3.9 N/C in order to move an electron. Find the distance the electron travels.

a) 0.82 m

b) 1.3 m

c) 1.3 × 10^–19 m

d) 23 m

14. 12.0 J of work are required to move a 4.0 C charge between two points in an electric field. Calculate the potential difference between these two points.

a) 3.0 V

b) 8.0 V

c) 16.0 V

d) 48 V

Part III—Calculations

Perform each of the following calculations.

15. A 3.50 µF capacitor has a charge with a magnitude of 4.50 µC on each parallel plate. Find the potential difference between the plates.

16. A capacitor stores 12.0 J of potential energy when the potential difference between the parallel plates is 9.0 V. Find the capacitance of the capacitor.

17. Two charged objects with charges of 2.5 µC and 0.45 µC, respectively, experience an electrostatic force of repulsion of 1.4 × 10^-4 N. What is the distance between the objects?

18. Find the intensity of an electric field in which an electron experiences a force of 6.0 N.

19. How much work would be required to move a charge of 4.0 C between two points in a circuit with a potential difference of 9.0 V?

20 An atom of oxygen contains 8 protons. What is the nuclear charge of an oxygen atom in coulombs?