Question 1

An atom has more protons than electrons. The atom is

Accepted Answer

A) a negative ion. 
B) a positive ion. 
C) an insulator. 
D) a conductor. 
E) a semiconductor. 
A) a negative ion. 
B) a positive ion. 
C) an insulator. 
D) a conductor. 
E) a semiconductor. B

Question 2

A dipole moment is placed in a uniform electric field oriented along an unknown direction. The maximum torque applied to the dipole is equal to 0.1 N.m. When the dipole reaches equilibrium its potential energy is equal to -0.2 J. What was the initial angle between the direction of the dipole moment and the direction of the electric field?

Accepted Answer

A) 10° 
B) 90° 
C) 45° 
D) 30° 
E) 0 
A) 10° 
B) 90° 
C) 45° 
D) 30° 
E) 0 D

Question 3

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

Accepted Answer

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

Question 4

A neutral atom always has

Accepted Answer

A) more neutrons than protons. 
B) more neutrons than electrons. 
C) more protons than electrons. 
D) the same number of neutrons as protons. 
E) the same number of protons as electrons. 
A) more neutrons than protons. 
B) more neutrons than electrons. 
C) more protons than electrons. 
D) the same number of neutrons as protons. 
E) the same number of protons as electrons.

Question 5

Two large, flat plates are parallel to each other. Plate A , located at y = 1 cm, is along the xz-plane and carries a uniform charge density σA = -1.00 μC/m2. Plate B is located at y = -1 cm and carries a uniform charge density σB = +2.00 μC/ m2. What is the electric field at the point of coordinates (x, y, z) = ( -0.5 cm, 0 cm, 0 cm)?

Accepted Answer

A) ( +1.13x 105 N/
C)    
B) ( -2.83x 105 N/
C)    
C) ( +1.19x 105 N/
C)    
D) ( +1.69x 105 N/
C)    
E) ( -1.19x 105 N/
C)    
A) ( +1.13x 105 N/
C)    
B) ( -2.83x 105 N/
C)    
C) ( +1.19x 105 N/
C)    
D) ( +1.69x 105 N/
C)    
E) ( -1.19x 105 N/
C)

Question 6

Compare insulators and conductors on the atomic level.

Accepted Answer

From the atomic point of view, the elect

Question 7

An originally neutral electroscope is briefly touched with a positively charged glass rod. The electroscope

Accepted Answer

A) remains neutral. 
B) becomes negatively charged. 
C) becomes positively charged. 
D) could become either positively or negatively charged, depending on the time of contact. 
A) remains neutral. 
B) becomes negatively charged. 
C) becomes positively charged. 
D) could become either positively or negatively charged, depending on the time of contact.

Question 8

A positive object touches a neutral electroscope, and the leaves separate. Then a negative object is brought near the electroscope, but does not touch it. What happens to the leaves?

Accepted Answer

A) They separate further. 
B) They move closer together. 
C) They are unaffected. 
D) cannot be determined without further information 
A) They separate further. 
B) They move closer together. 
C) They are unaffected. 
D) cannot be determined without further information

Question 9

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?

Accepted Answer

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

Question 10

An originally neutral electroscope is grounded briefly while a positively charged glass rod is held near it. After the glass rod is removed, the electroscope

Accepted Answer

A) remains neutral. 
B) is negatively charged. 
C) is positively charged. 
D) could be either positively or negatively charged, depending on how long the contact with ground lasted. 
A) remains neutral. 
B) is negatively charged. 
C) is positively charged. 
D) could be either positively or negatively charged, depending on how long the contact with ground lasted.

Question 11

FIGURE 21-9  
-Three equal point charges are placed at three of the corners of a square of side d as shown in Fig. 21-9. Which of the arrows shown represents the direction of the net electric field at the center of the square?

Accepted Answer

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

Question 12

FIGURE 21-13  
-The electric field shown in Fig. 21-13

Accepted Answer

A) increases to the right. 
B) increases down. 
C) decreases to the right. 
D) decreases down. 
E) is uniform. 
A) increases to the right. 
B) increases down. 
C) decreases to the right. 
D) decreases down. 
E) is uniform.

Question 13

Materials in which the electrons are bound very loosely to the nuclei and can move about freely within the material are referred to as

Accepted Answer

A) insulators. 
B) conductors. 
C) semiconductors. 
D) superconductors. 
E) polar. 
A) insulators. 
B) conductors. 
C) semiconductors. 
D) superconductors. 
E) polar.

Question 14

Two large, flat, horizontally oriented plates are parallel to each other, a distance d apart. Half-way between the two plates the electric field field has a magnitude E. If the separation of the plates is reduced to d/2 what is the magnitude of the electric field half-way between the plates?

Accepted Answer

A) 4E 
B) E/2 
C) 0 
D) 2E 
E) E 
A) 4E 
B) E/2 
C) 0 
D) 2E 
E) E

Question 15

Is it possible to have a zero electric field value between a negative and positive charge along the line joining the two charges?

Accepted Answer

A) Yes, if the two charges are equal in magnitude. 
B) Yes, regardless of the magnitude of the two charges. 
C) No, a zero electric field cannot exist between the two charges. 
D) cannot be determined without knowing the separation between the two charges 
E) cannot be determined without knowing the magnitude of the charges 
A) Yes, if the two charges are equal in magnitude. 
B) Yes, regardless of the magnitude of the two charges. 
C) No, a zero electric field cannot exist between the two charges. 
D) cannot be determined without knowing the separation between the two charges 
E) cannot be determined without knowing the magnitude of the charges

Question 16

A 10 microcoulomb charge is placed at the origin and a 20 microcoulomb charge is placed on the x-axis at x = 40 cm. If an electron is placed on the y-axis at y = 30 cm, what is the magnitude of the force it will experience?

Accepted Answer

A) 0.615 × 10-12 N 
B) 2.46 × 10-13 N 
C) 4.92 × 10-13 N 
D) 1.23 × 10-13 N 
E) 2.46 × 10-14 N 
A) 0.615 × 10-12 N 
B) 2.46 × 10-13 N 
C) 4.92 × 10-13 N 
D) 1.23 × 10-13 N 
E) 2.46 × 10-14 N

Question 17

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?

Accepted Answer

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

Question 18

A solid block of metal in electrostatic equilibrium is placed in a uniform electric field. Give a statement concerning the electric field in the block's interior.

Accepted Answer

A) The interior field points in a direction opposite to the exterior field. 
B) The interior field points in a direction that is at right angles to the exterior field. 
C) The interior points in a direction that is parallel to the exterior field. 
D) There is no electric field in the block's interior. 
E) Not enough information is given to make a statement concerning the elecric field on the block's interior. 
A) The interior field points in a direction opposite to the exterior field. 
B) The interior field points in a direction that is at right angles to the exterior field. 
C) The interior points in a direction that is parallel to the exterior field. 
D) There is no electric field in the block's interior. 
E) Not enough information is given to make a statement concerning the elecric field on the block's interior.

Question 19

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

Accepted Answer

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

Question 20

Equal charges are located at the vertices of a 3-4-5 triangle. The charge experiencing the largest force is located at

Accepted Answer

A) the 90° vertex. 
B) the 37° vertex. 
C) a vertex that depends on the size of the charges. 
D) the 53° vertex. 
E) cannot be determined. 
A) the 90° vertex. 
B) the 37° vertex. 
C) a vertex that depends on the size of the charges. 
D) the 53° vertex. 
E) cannot be determined.

Exam 21: Electric Charge and Electric Field

An atom has more protons than electrons. The atom is

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 neutral atom always has

Compare insulators and conductors on the atomic level.

An originally neutral electroscope is briefly touched with a positively charged glass rod. The electroscope

A positive object touches a neutral electroscope, and the leaves separate. Then a negative object is brought near the electroscope, but does not touch it. What happens to the leaves?

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?

An originally neutral electroscope is grounded briefly while a positively charged glass rod is held near it. After the glass rod is removed, the electroscope

FIGURE 21-9 -Three equal point charges are placed at three of the corners of a square of side d as shown in Fig. 21-9. Which of the arrows shown represents the direction of the net electric field at the center of the square?

FIGURE 21-13 -The electric field shown in Fig. 21-13

Materials in which the electrons are bound very loosely to the nuclei and can move about freely within the material are referred to as

Two large, flat, horizontally oriented plates are parallel to each other, a distance d apart. Half-way between the two plates the electric field field has a magnitude E. If the separation of the plates is reduced to d/2 what is the magnitude of the electric field half-way between the plates?

Is it possible to have a zero electric field value between a negative and positive charge along the line joining the two charges?

A 10 microcoulomb charge is placed at the origin and a 20 microcoulomb charge is placed on the x-axis at x = 40 cm. If an electron is placed on the y-axis at y = 30 cm, what is the magnitude of the force it will experience?

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 solid block of metal in electrostatic equilibrium is placed in a uniform electric field. Give a statement concerning the electric field in the block's interior.

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

Equal charges are located at the vertices of a 3-4-5 triangle. The charge experiencing the largest force is located at

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