Test Bank all Chapter

College Physics Reasoning and Relationships, 2e (Volume 2) By Nicholas Giordano

(Test Bank all Chapter)

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Chapter 17: Electric Forces and Fields

MULTIPLE CHOICE

17.1 Evidence for Electric Forces: The Observational Facts

• Doug rubs a piece of fur on a hard rubber rod, giving the rod a negative charge. What happens?
• Protons are removed from the rod. c. Electrons are added to the rod.
• The fur is left neutral. d. The fur is also charged negatively.

ANS: C PTS: 1 DIF: 1

• A repelling force must occur between two charged objects under which conditions?
• Charges are of equal magnitude. c. Charges are of unequal magnitude.
• Charges are of unlike signs. d. Charges are of like signs.

ANS: D PTS: 1 DIF: 1

• A metallic object holds a charge of −2.9  10

−5

• What total number of electrons does this represent?

(e = 1.6  10 −19 C is the magnitude of the electronic charge.)

• 1.8  10

14

• 6.1  10

13

• 2.4  10

13

• 4.2  10

14

ANS: A PTS: 1 DIF: 2

• About how many electrons are in 0.3 gram of water (H2O)?
• 10

23

• 10

25

• 10

21

• 10

19

ANS: A PTS: 1 DIF: 3

• The charge per unit length on an insulator is . On a 2.0-m length of this material, what is the

difference in the number of electrons and the number of protons?a.There are more electrons than protons.b.There are more protons than electrons.c.There are more protons than electrons.d.There are more electrons than protons.

ANS: B PTS: 1 DIF: 2

17.2 Electric Forces and Coulomb’s Law

• Object A has a charge q on it, object B has a charge q on it, and object C has a charge 2q on it. These

charges are arranged, one each, at the vertices of an equilateral triangle. Which charge has the greatest magnitude electric force on it?

• A
• C
• B
• All have equal magnitude forces on them.

ANS: B PTS: 1 DIF: 2

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• Two point charges are 4 cm apart. They are moved to a new separation of 8 cm. By what factor does

the resulting mutual force between them change?

• 1/4 c. 1/2
• 2 d. 4

ANS: A PTS: 1 DIF: 1

• If the distance between two point charges is quadrupled, the mutual force between them will be

changed by what factor?

• 8 c. 1/16
• 4 d. 1/4

ANS: C PTS: 1 DIF: 1

• If the size of the charge value is tripled for one of two point charges maintained at a constant

separation, the mutual force between them will be changed by what factor?

• 3.0 c. 9.0
• 1/9 d. 0.33

ANS: A PTS: 1 DIF: 1

• The constant ke, which appears in Coulomb’s law formula, is equivalent dimensionally to which of the

following?

• N/C c. N/C

2

• Nm

2 /C 2

• Nm/C

ANS: B PTS: 1 DIF: 1

• Two point charges, separated by 15 cm, have charge values of +2.0 µC and −4.0 µC, respectively.

What is the value of the mutual force between them? (ke = 8.99  10 9 Nm 2 /C 2 )

• 8.0  10

−12 N c. 320 N

• 3.6  10

−8 N d. 3.2 N

ANS: D PTS: 1 DIF: 2

• Four charges are at the corners of a square, with B and C on opposite corners. Charges A and D, on the

other two corners, have equal charge, while both B and C have a charge of +1.0 C. What is the charge on A so that the force on B is zero?

• −0.50 C c. −1.0 C
• −0.71 C d. −0.35 C

ANS: D PTS: 1 DIF: 3

• Charge A and charge B are 3.00 m apart, and charge A is +2.00 C and charge B is +3.00 C. Charge C

is located between them at a certain point and the force on charge C is zero. How far from charge B is charge C?

• 1.35 m c. 1.65 m
• 0.667 m d. 0.555 m

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ANS: C PTS: 1 DIF: 3

• In a thundercloud there may be an electric charge of +40 C near the top of the cloud and −40 C near

the bottom of the cloud. These charges are separated by about 2.0 km. What is the electric force between these two sets of charges? (ke = 8.99  10 9 N·m 2 /C 2 )

• 3.6  10

6 N c. 3.6  10 7 N

• 3.6  10

4 N d. 3.6  10 5 N

ANS: A PTS: 1 DIF: 2

• An electron is sent at high speed toward a gold nucleus (charge +79e). What is the electrical force

acting on the electron when it is 3.0  10 −13 m away from the gold nucleus? (e = 1.6  10 −19 C, ke =

8.99  10

9 N·m 2 /C 2 )

• 2.1  10

−6 N c. 0.20 N

• 2.0  10

−4 N d. 20 N

ANS: C PTS: 1 DIF: 2

• Two electrons are separated by one cm. What is the ratio of the electric force to the gravitational force

between them? (me = 9.11  10 −31 kg, ke = 8.99  10 9 Nm 2 /C 2

, G = 6.67  10

-11 Nm 2 /kg 2 , and e = 1.6

 10

−19 C)

• 1.3  10

20

• 2.3  10

2

• 4.2  10

42

• 3.1  10

22

ANS: B PTS: 1 DIF: 2

• Two equal charges, each Q, are separated by some distance. What third charge would need to be

placed half way between the two charges so that the net force on each charge would be zero?

• −Q/8 c. −Q/4
• −Q d. −Q/2

ANS: C PTS: 1 DIF: 2

• A 6.0-mC charge is placed at the origin and a second charge is placed on the x axis at x = 0.30 m. If the

resulting force on the second charge is 5.4 N in the positive x direction, what is the value of its charge?

• 9.0 nC c. 9.0 C
• –9.0 nC d. –9.0 C

ANS: A PTS: 1 DIF: 2

• A 6.00-C charge is placed at the origin and a second charge is placed on the x axis at x = 0.300 m. If

the resulting force on the second charge is 6.40 N in the negative x direction, what is the force on the charge at the origin?

• 6.40 N in the negative x direction
• 0 N
• 6.40 N in the positive x direction
• not able to be determined until the second charge is known

ANS: C PTS: 1 DIF: 2

• Two identical spheres each carry a charge of −40.0 µC. The spheres are separated by a distance of 2.00
• What is the electric force between the spheres? (ke = 8.99  10

9 N·m 2 /C 2 )

• 43.2 N (attractive) c. 3.60 N (repulsive)
• 14.4 N (repulsive) d. 7.19 N (attractive)

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