Deck 19: Electric Charges, Forces, and Fields

Question 1

Electrical and gravitational forces follow similar equations with one main difference:

A) Electrical forces obey the inverse square law and gravitational forces do not.
B) Gravitational forces obey the inverse square law and electrical forces do not.
C) Electrical forces attract and gravitational forces repel.
D) Electrical forces repel and gravitational forces attract.
E) Gravitational forces are always attractive but electrical forces can be attractive or repulsive.

Answer 1

Gravitational forces are always attractive but electrical forces can be attractive or repulsive.

Question 2

A neutron carries a negative charge.

Answer 2

False

Question 3

An electrically neutral atom does not have a net charge.

Answer 3

True

Question 4

When atom A loses an electron to atom B,

A) atom A becomes more negative than atom B.
B) atom A acquires more neutrons than atom B.
C) atom A acquires less neutrons than atom B.
D) atom A becomes a positive ion and atom B becomes a negative ion.
E) atom A becomes a negative ion and atom B becomes a positive ion.

Question 5

The Coulomb force between two charges can be attractive or repulsive.

Question 6

The charge on the proton is the same as

A) the charge on the neutron.
B) the charge on the neutron, but of the opposite sign.
C) the charge on the atom.
D) the charge on the electron.
E) the charge on the electron, but of the opposite sign.

Question 7

If a conductor is placed in an electric field under electrostatic conditions, the electric field is excluded from the inside of the conductor.

Question 8

The main difference between conductors and insulators is in terms of

A) protons.
B) neutrons.
C) valence or conduction electrons.
D) atoms.
E) None of the other choices is correct.

Question 9

The electric field is continuous.

Question 10

A good conductor of electricity is a bad conductor of heat.

Question 11

Two charges, Q₁ and Q₂, are separated by a certain distance R. If the magnitudes of the charges are doubled and their separation is also doubled, then what happens to the electrical force between these two charges?

A) It is doubled.
B) It changes by a factor of 3.
C) reduced by a factor of .
D) It is quadrupled.
E) It remains the same.

Question 12

Two charges, Q₁ and Q₂, are separated by a certain distance R. If the magnitudes of the charges are halved, and their separation is also halved, then what happens to the electrical force between these charges?

A) It increases by a factor of 16.
B) It increases by a factor of 8.
C) It is doubled.
D) It is quadrupled.
E) It remains the same.

Question 13

A neutron is approximately twice as heavy as the electron.

Question 14

Electric field lines and equipotential lines meet perpendicular to one another.

Question 15

The number of protons in the nucleus of an electrically neutral atom is equal to

A) the number of neutrons in the nucleus.
B) the number of neutrons surrounding the nucleus.
C) the number of electrons surrounding the nucleus.
D) the number of electrons in the nucleus.
E) None of the other choices is correct.

Question 16

A positive charge placed in an electric field experiences a force in the direction of the field.

Question 17

When the distance between the two charges is doubled, the force between them is

A) doubled.
B) quadrupled.
C) reduced by a factor of 3.
D) reduced by a factor of .
E) reduced by a factor of 4.

Question 18

When the magnitude of both interacting charges is increased by a factor of 2, the electrical forces between these charges is

A) doubled.
B) quadrupled.
C) reduced by a factor of 3.
D) reduced by a factor of .
E) reduced by a factor of 4.

Question 19

Two objects, A and B, are rubbed together. As a result, object A acquires an excess negative charge while object B becomes positively charged. In comparison to their masses before the charging process, you can say that

A) the mass of both objects increased.
B) the mass of A increased and that of B decreased.
C) the mass of A decreased and that of B increased.
D) the mass of both objects decreased.
E) None of the other choices is correct.

Question 20

Electric charge is quantized.

Question 21

FIGURE 19-3
Four point charges of equal magnitude but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in Figure 19-3. Which of the arrows shown represents the net force acting on the center charge?

A) A
B) B
C) C
D) D
E) none of the above

Question 22

By what method will a positively charged rod produce a negative charge on a conducting sphere that is placed on an insulating surface?

A) by means of conduction
B) by means of convection
C) by means of induction
D) None of the other choices is correct.

Question 23

FIGURE 19-5
Four point charges of equal magnitude and sign are arranged on the corners of the square of side d as shown in Figure 19-5. Which of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 24

FIGURE 19-12
Which of the arrows shown in Figure 19-12 represents the correct direction of the electric field between the two metal plates?

A) A
B) B
C) C
D) D
E) none of the above

Question 25

A charged particle traveling along the +x axis enters an electric field directed vertically upward along the +y-axis. If the charged particle experiences a force downward because of this field, what is the sign of the charge on this particle?

A) It is negative.
B) It is positive.
C) It is neutral.
D) None of the other choices is correct.

Question 26

FIGURE 19-11
Three equal point charges of varying signs are placed on three of the corners of a square of side d as shown in Figure 19-11. Which of the arrows shown represents the direction of the net electric field at the vacant corner of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 27

FIGURE 19-4
Four point charges of equal magnitude and sign are arranged on three of the corners of the square of side d as shown in Figure 19-4. Which of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 28

FIGURE 19-13
Figure 19-13 shows four Gaussian surfaces surrounding a distribution of charges. Which Gaussian surfaces have an electric flux of +q/ε_o through them?

A) a
B) b
C) c
D) b and d
E) b and c

Question 29

An electron traveling along the +x-axis enters an electric field that is directed vertically down, i.e., along the negative y-axis. What will be the direction of the electric force acting on the electron after entering the electric field?

A) downward
B) upward
C) to the left
D) to the right
E) into the page

Question 30

FIGURE 19-6
Four point charges of varying magnitude and sign are arranged on the corners of the square of side d as shown in Figure 19-6. Which of the arrows shown represents the net force acting on the point charge with a charge +Q?

A) A
B) B
C) C
D) D
E) none of the above

Question 31

FIGURE 19-2
Four point charges of equal magnitudes but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in Figure 19-2. Which of the arrows shown represents the net force acting on the center charge?

A) A
B) B
C) C
D) D
E) none of the above

Question 32

FIGURE 19-10
Three equal point charges are placed at three of the corners of a square of side d as shown in Figure 19-10. Which of the arrows shown represents the direction of the net electric field at the vacant corner of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 33

FIGURE 19-9
Three equal point charges are placed at three of the corners of a square of side d as shown in Figure 19-9. Which of the arrows shown represents the direction of the net electric field at the center of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 34

FIGURE 19-8
Three equal point charges of varying signs are placed on the corners of a square of side d as shown in Figure 19-8. Which of the arrows shown represents the direction of the net electric field at the center of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 35

A conductor is placed in an electric field under electrostatic conditions. Which of the following statements is correct for this situation?

A) The electric field is zero inside the conductor.
B) All valence electrons go to the surface of the conductor.
C) The electric field on the surface of the conductor is perpendicular to the surface.
D) All of the other answers apply.

Question 36

A charged rod carrying a negative charge is brought near two spheres that are in contact with each other but insulated from the ground. If the two spheres are then separated, what kind of charge will be on the spheres?

A) The sphere near the charged rod becomes positive and the other becomes negative.
B) The sphere near the charged rod becomes negative and the other becomes positive.
C) The spheres do not get any charge.
D) None of the other choices is correct.

Question 37

Four equal charges are located at the corners of a square of side d. If the magnitude of each charge is doubled, then what happens to the resultant force on each charge?

A) It is doubled.
B) It is quadrupled.
C) It increases by a factor of 8.
D) It remains the same.
E) None of the other choices is correct.

Question 38

Figure 19-13 shows four Gaussian surfaces surrounding a distribution of charges. Which Gaussian surfaces have no electric flux through them?

A) a
B) b
C) c
D) b and d
E) b and c

Question 39

FIGURE 19-7
Three equal point charges are placed at the corners of a square of side d as shown in Figure 19-7. Which of the arrows shown represents the direction of the net electric field at the center of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 40

FIGURE 19-1
Three equal charges are at three of the corners of a square of side d. A fourth charge of equal magnitude is at the center of the square as shown in Figure 19-1. Which of the arrows shown represents the net force acting on the charge at the center of the square?

A) A
B) B
C) C
D) D
E) none of the above

Question 41

Three 3.0 μC charges are at the three corners of an square of side 0.50 m. The last corner is occupied by a -3.0 μC charge. Find the electric field at the center of the square.

Question 42

A piece of plastic has a net charge of +2.00 μC. How many more protons than electrons does this piece of plastic have?

A) 1.25 × 10¹³
B) 1.25 × 10¹⁹
C) 2.50 × 10¹³
D) 2.50 × 10¹⁹
E) 0

Question 43

Conductor A has 16 electrons and conductor B has 32 electrons. The ratio of the valence electrons of conductor A and conductor B is given as

A) 1:2.
B) 2:1.
C) 1:3.
D) 3:1.
E) 3:2.

Question 44

Gaussian surfaces A and B enclose the same positive charge +Q. The area of Gaussian surface A is three times larger than that of Gaussian surface B. The flux of electric field through Gaussian surface A is

A) nine times larger than the flux of electric field through Gaussian surface B.
B) three times larger than the flux of electric field through Gaussian surface B.
C) equal to the flux of electric field through Gaussian surface B.
D) three times smaller than the flux of electric field through Gaussian surface B.
E) unrelated to the flux of electric field through Gaussian surface B.

Question 45

Three point charges are placed on the x-axis. A charge of +2.0 μC is placed at the origin, -2.0 μC to the right at x = 50 cm, and +4.0 μC at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin?

Question 46

A 5.0-μC charge is placed at the 0 cm mark of a meter stick and a -4.0 μC charge is placed at the 50 cm mark. At what point on a line joining the two charges is the electric field zero?

Question 47

There is a 5.0 μC charge at each of 3 corners of a square (each side 70. mm long). What is the force on +6.0 μC placed at the center of the square?

Question 48

Thirty microcoulombs of NEGATIVE charge experiences an electrostatic force of 27. mN. What is the magnitude and direction of the electric field?

Question 49

Consider the x-axis with 4.0 μC at x = 1.0 meter and -2.0 μC at the origin. Where should 6.0 μC be placed so that the net force on it is zero?

Question 50

How far apart should two protons be if the electrical force of repulsion is equal to the weight (attraction to the Earth) of one of the protons?

Question 51

Two large parallel metal plates are uniformly and oppositely charged and the electric field between them is 7.6 × 10⁶ N/C.
(a) What is the charge density on each plate?
(b) If the very large charged plates are moved 2 times farther apart, what is the electric field between the plates now?

Question 52

A metal sphere of radius 2.0 cm carries a charge of 3.0 μC. What is the electric field 6.0 cm from the center of the sphere?

Question 53

The charge carried by one electron is e = -1.6 × 10^-19 C. The number of electrons necessary to produce a charge of -1.0 C is

A) 6.3 × 10¹⁸.
B) 6.3 × 10⁹.
C) 1.6 × 10¹⁹.
D) 1.6 × 10⁹.
E) none of the above

Question 54

An electron is placed in a constant electric field of 4.5 × 10⁴ N/C.
(a) What is the force on the electron?
(b) If the electron is released from rest, what is its speed after 3.0 ps?

Question 55

Two equal charges of magnitude +1 C are separated by a distance of 1 km. What is the force acting between these two charges?

A) 0.9 N
B) 9 N
C) 90 N
D) 900 N
E) 9000 N

Question 56

Q₁ = 6.0 nC is at (0.30 m, 0); Q₂ = -1.0 nC is at (0, 0.10 m); Q₃ = 5.0 nC is at (0, 0). What is the magnitude and direction of the net force on the 5.0 nC charge?

Question 57

Consider an equilateral triangle of side 20. cm. A charge of +2.0 μC is placed at one vertex and charges of -4.0 μC are placed at the other two vertices. Determine the magnitude and direction of the electric field at the center of the triangle.

Question 58

Conductor A has 11 electrons and conductor B has 32 electrons. The number of valence or conduction electrons in A and B is given as

A) A:2 and B:4.
B) A:4 and B:2.
C) A:4 and B:4.
D) A:1 and B:4.
E) A:4 and B:1.

Question 59

An atomic nucleus has a charge of +40e. An electron is 10^-9 m from the nucleus. What is the force on the electron?

A) 2.9 nN
B) 1000 C
C) 3.7 nN
D) 6.8 nN
E) 9.2 nN

Question 60

A 5.0-C charge is 10 m from a small test charge. What is the magnitude and direction of the electric field at the location of the test charge?

Question 61

A proton is placed in an electric field of intensity 700 N/C. What is the magnitude and direction of the acceleration of this proton due to this field?

A) 6.71 × 10⁹ m/s² opposite to the electric field
B) 6.71 × 10¹⁰ m/s² opposite to the electric field
C) 6.71 × 10¹⁰ m/s² in the direction of the electric field
D) 67.1 × 10¹⁰ m/s² opposite to the electric field
E) 67.1 × 10¹⁰ m/s² in the direction of the electric field

Question 62

A point charge Q = 7.00 × 10^-9 C is placed at the origin of an xy-coordinate system. What is the electric field intensity E at a distance of x = 30 cm from this charge? (Use k = 9 × 10⁹ Nm²/C².)

A) 100 N/C
B) 400 N/C
C) 500 N/C
D) 600 N/C
E) 700 N/C

Question 63

FIGURE 19-14
Two point charges of magnitudes + 5.00 μC, and + 7.00 μC are placed along the x-axis at x = 0 cm and x = 100 cm, respectively. Where must a third charge be placed along the x-axis so that it does not experience any net force because of the other two charges?

A) 4.58 cm
B) 45.8 cm
C) 50 cm
D) 9.12 cm
E) 91.2 cm

Question 64

What are the magnitude and direction of the electric field at a distance of 1.50 m from a 50.0-nC charge?

A) 20 N/C away from the charge
B) 20 N/C toward from the charge
C) 10 N/C away from the charge
D) 200 N/C away from the charge
E) 200 N/C toward from the charge

Question 65

The force of attraction between a - 40.0 μC and + 108 μC charge is 4.00 N. What is the separation between these two charges?

A) 2.10 m
B) 3.67 m
C) 3.12 m
D) 2.49 m
E) 1.13 m

Question 66

A force of 6.0 N acts on a charge of 3.0 μC when it is placed in a uniform electric field. What is the magnitude of this electric field?

A) 18 MN/C
B) 2.0 MN/C
C) 1.0 MN/C
D) 0.50 MN/C
E) 130 MN/C

Question 67

Q₁ = 6.0 nC is at (0.30 m, 0); Q₂ = -1.0 nC is at (0, 0.10 m); Q₃ = 5.0 nC is at (0, 0). What is the direction of the net force on the 5.0 nC charge?

A) 34° above +x-axis
B) 34° above -x-axis
C) along the -x-axis
D) 56° above +x-axis
E) 56° above -x-axis

Question 68

Two point charges of + 40.0 μC and - 10.0 μC are separated by a distance of 20.0 cm. A +7.00 μC charge is placed midway between these two charges. What is the electric force acting on this charge because of the other two charges?

A) 0.453 N directed towards the negative charge
B) 3.15 N directed towards the negative charge
C) 3.15 N directed towards the positive charge
D) 315 N directed towards the positive charge
E) 315 N directed towards the negative charge

Question 69

The ratio of electrical force, F_e, to the gravitational force F_g, between two electrons is

A) 2.1 × 10⁴²
B) 4.2 × 10⁴²
C) 6.3 × 10⁴²
D) 8.4 × 10⁴²
E) 9.8 × 10⁴²

Question 70

Three point charges are located at the following positions: Q₁ = 2.00 μC at x = 1.00 m; Q₂ = 3.00 μC at x = 0; Q₃ = -5.00 μC at x = -1.00 m. What is the magnitude of the force on the 3.00-μC charge?

A) 5.40 × 10^-2 N
B) 0.135 N
C) 0.158 N
D) 8.10 × 10^-2 N
E) 0.189 N

Question 71

Two point charges, initially 2.0 cm apart, experience a 1.0-N force. If they are moved to a new separation of 8.0 cm, what is the electric force between them?

A) 2.0 N
B) 4.0 N
C) 16 N
D) 1/4 N
E) 1/16 N

Question 72

A 1.0-C charge is 15 m from a second charge, and the force between them is 1.0 N. What is the magnitude of the second charge?

A) 25 C
B) 1.0 C
C) 10 nC
D) 0.025 C
E) 25 nC

Question 73

Two point charges of + 20.0 μC and - 8.00 μC are separated by a distance of 20.0 cm. What is the intensity of electric field E midway between these two charges?

A) 25.2 × 10⁶ N/C directed towards the negative charge
B) 25.2 × 10⁶N/C directed towards the positive charge
C) 25.2 × 10⁵ N/C directed towards the negative charge
D) 25.2 × 10⁵ N/C directed towards the positive charge
E) 25.2 × 10⁴ N/C directed towards the negative charge

Question 74

Three point charges are placed on the x-axis. A charge of +2.0 μC is placed at the origin, -2.0 μC to the right at x = 50 cm, and +4.0 μC at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin?

A) 0.072 N right
B) 0.072 N left
C) 0.14 N right
D) 0.14 N left
E) 0

Question 75

FIGURE 19-14
Two point charges of magnitude + 7.00 μC and - 9.00 μC are placed along the x-axis at x = 0 cm and x = 40.0 cm, respectively. Where must a third charge, q, be placed along the x-axis so that it does not experience any net force because of the other two charges?

A) 0.200 m
B) 2.99 m
C) - 0.187 m
D) - 2.99 m
E) 0.187 m

Question 76

FIGURE 19-14
Three point charges of magnitude +2.0 μC, +3.0 μC, +4.0 μC are located at the corners of a triangle as shown in Figure 19-14 The resultant force acting on the +4.0 μC charge is given by

A) 1.8 N at 97° with the +y-axis.
B) 2.7 N at 97° with the +x-axis.
C) 2.7 N at 97° with the +y-axis.
D) 3.9 N at 97° with the +y-axis.
E) 3.9 N at 97° with the +x-axis.

Question 77

Two coins carry identical charges. These two coins are lying 2.50 m apart on a table. If each of these coins experiences a force of 2.00 N, how large is the charge on each coin?

A) 2.61 μC
B) 26.1 μC
C) 6.67 μC
D) 5.22 μC
E) 52.2 μC

Question 78

Q₁ = 6.0 nC is at (0.30 m, 0); Q₂ = -1.0 nC is at (0, 0.10 m); Q₃ = 5.0 nC is at (0, 0). What is the magnitude of the net force on the 5.0 nC charge?

A) 3.0 × 10^-6 N
B) 4.5 × 10^-6 N
C) 5.4 × 10^-6 N
D) 7.2 × 10^-6 N
E) 9.0 × 10^-6 N

Question 79

Three point charges of magnitudes + 4.0 μC, - 5.0 μC, and - 9.0 μC are placed on the x-axis at x = 0 cm, x = 40 cm, and x = 120 cm, respectively. What is the force on the - 9.0 μC charge due to the other two charges?

A) -0.55 N
B) 0.55 N
C) 0.64 N
D) 0.41 N
E) - 0.41 N

Question 80

Three identical charges of 3.0 μC are placed at the vertices of an equilateral triangle which measures 30 cm on a side. What is the magnitude of the electrostatic force which acts on any one of the charges?

A) 1.6 N
B) 1.8 N
C) 2.0 N
D) 2.2 N
E) 2.4 N