Question 1

The reaction 8p+ + 6e- → 2p+ violates charge conservation because there are more charges before the reaction than afterwards.

Accepted Answer

A) True 
 B)False

Question 2

A 3.0 μC positive charge is located at the origin and a 2.0 μC positive charge is located at x = 0.0 m,y = 1.0 m.Find the point between them where the electric field strength is zero.

Accepted Answer

A) x = 0 m,y = 0.55 m 
B) x = 0 m,y = 0.67 m 
C) x = 0 m,y = 1.5 m 
D) x = 0 m,y = 0.60 m 
A) x = 0 m,y = 0.55 m 
B) x = 0 m,y = 0.67 m 
C) x = 0 m,y = 1.5 m 
D) x = 0 m,y = 0.60 m

Question 3

What is the strength of an electric field that a 0.010 C negative charge experiences 0.90 mm from a 0.20 C positive charge? (The value of K is 9.0 × 109 N·m2/C2. )

Accepted Answer

A) 2.2 × 1015 N/C 
B) 5.6 × 1016 N/C 
C) 1.1 × 1015 N/C 
D) 2.2 × 1016 N/C 
A) 2.2 × 1015 N/C 
B) 5.6 × 1016 N/C 
C) 1.1 × 1015 N/C 
D) 2.2 × 1016 N/C

Question 4

Two electrons are passing 26.0 mm apart.What is the electric repulsive force that they exert on each other? (The value of k is 9.0 × 109 N·m2/C2. )

Accepted Answer

A) 3.4 × 10-25 N 
B) 1.3 × 1010 N 
C) 1.3 N 
D) 3.4 × 10-27 N 
A) 3.4 × 10-25 N 
B) 1.3 × 1010 N 
C) 1.3 N 
D) 3.4 × 10-27 N

Question 5

The figure shows two 5.0 g spheres suspended from 1.0-m-long threads.The spheres repel each other after being charged to +91 nC.What is the angle θ?

Accepted Answer

A) 4.1 degrees 
B) 8.2 degrees 
C) 12 degrees 
D) 16 degrees 
A) 4.1 degrees 
B) 8.2 degrees 
C) 12 degrees 
D) 16 degrees

Question 6

The diagram shows electric field lines arising from two small charged particles P and Q.   Consider the following two statements: 
i.The charge on P is smaller than the charge on Q.
Ii.The electrostatic force on P is smaller than that on Q.
Which of the above statements are true?

Accepted Answer

A) Only i 
B) Only ii 
C) Both i and ii 
D) Neither i nor ii 
A) Only i 
B) Only ii 
C) Both i and ii 
D) Neither i nor ii

Question 7

If you rub a balloon on your sweater and then press it to a wall,it will often stick there.Why does this happen?

Accepted Answer

A) Rubbing removes a surface layer of grease,allowing the rubber to come in sufficiently close contact with the wall so that air pressure holds it there. 
B) Rubbing the balloon charges it electrostatically,and this charge on the balloon induces an opposite charge on the wall.The attraction between the induced charge and the charge on the balloon holds the balloon to the wall. 
C) A wall typically has a net electric charge on it,and rubbing the balloon charges it electrostatically.If the wall happens to have opposite charge to that on the balloon,the balloon will stick. 
D) Rubbing the balloon causes moisture to condense on it,and surface tension causes the balloon to stick to the wall. 
E) Rubbing the balloon surface causes it to become slightly conducting.When the balloon is touched to the wall,electrons flow from the balloon to the wall.This sets up an electric field that bonds the balloon weakly to the wall. 
A) Rubbing removes a surface layer of grease,allowing the rubber to come in sufficiently close contact with the wall so that air pressure holds it there. 
B) Rubbing the balloon charges it electrostatically,and this charge on the balloon induces an opposite charge on the wall.The attraction between the induced charge and the charge on the balloon holds the balloon to the wall. 
C) A wall typically has a net electric charge on it,and rubbing the balloon charges it electrostatically.If the wall happens to have opposite charge to that on the balloon,the balloon will stick. 
D) Rubbing the balloon causes moisture to condense on it,and surface tension causes the balloon to stick to the wall. 
E) Rubbing the balloon surface causes it to become slightly conducting.When the balloon is touched to the wall,electrons flow from the balloon to the wall.This sets up an electric field that bonds the balloon weakly to the wall.

Question 8

It is impossible for any object to have a charge of 7.5 e.

Accepted Answer

A) True 
 B)False

Question 9

An electron is initially moving to the right when it enters a uniform electric field directed upwards.Which trajectory shown below will the electron follow?

Accepted Answer

A) Trajectory W 
B) Trajectory X 
C) Trajectory Y 
D) Trajectory Z 
A) Trajectory W 
B) Trajectory X 
C) Trajectory Y 
D) Trajectory Z

Question 10

If two macroscopic objects are electrically attracted to each other,

Accepted Answer

A) both objects must be negatively charged. 
B) both objects must be positively charged. 
C) one object must be negatively charged and the other object must be positively charged. 
D) None of the above statements are absolutely true. 
A) both objects must be negatively charged. 
B) both objects must be positively charged. 
C) one object must be negatively charged and the other object must be positively charged. 
D) None of the above statements are absolutely true.

Question 11

In the figure Q = 5.8 nC and all other quantities are exact.What is the magnitude of the force on the charge Q?

Accepted Answer

A) 1.8 × 10-3 N 
B) 1.0 × 10-3 N 
C) 9.0 × 10-4 N 
D) 1.2 × 10-3 N 
A) 1.8 × 10-3 N 
B) 1.0 × 10-3 N 
C) 9.0 × 10-4 N 
D) 1.2 × 10-3 N

Question 12

The electric field 2.8 cm from a small object points toward the object with a strength of 180,000 N/C.What is the object's charge?

Accepted Answer

A) - 16 nC 
B) + 16 nC 
C) - 17 nC 
D) + 17 nC 
A) - 16 nC 
B) + 16 nC 
C) - 17 nC 
D) + 17 nC

Question 13

Three point charges are at the vertices of an equilateral triangle.If the electric field at the midpoint of any side of this triangle points perpendicular to that side away from the inside of the triangle,you can conclude that these three charges have the same amount of charge and are all negative.

Accepted Answer

A) True 
 B)False

Question 14

If the electric field strength produced by a point charge is 1000 N/C at 5.0 cm from this charge,the strength will be 25,000 N/C at a point 1.0 cm closer to this charge.

Accepted Answer

A) True 
 B)False

Question 15

Two uncharged metal spheres,#1 and #2,are mounted on insulating support rods.A third metal sphere,carrying a positive charge,is then placed near #2.Now a copper wire is momentarily connected between #1 and #2 and then removed.Finally,sphere #3 is removed.In this final state

Accepted Answer

A) spheres #1 and #2 are still uncharged. 
B) sphere #1 carries positive charge and #2 carries negative charge. 
C) sphere #1 carries negative charge and #2 carries positive charge. 
D) spheres #1 and #2 both carry positive charge. 
E) spheres #1 and #2 both carry negative charge. 
A) spheres #1 and #2 are still uncharged. 
B) sphere #1 carries positive charge and #2 carries negative charge. 
C) sphere #1 carries negative charge and #2 carries positive charge. 
D) spheres #1 and #2 both carry positive charge. 
E) spheres #1 and #2 both carry negative charge.

Question 16

-A point charge Q = -12 μC,and two other charges,q1 and q2,are placed as shown.The electric force components on charge Q are Fx = +0.005 N and Fy = -0.003 N.In the figure,the number of excess electrons in charge Q is closest to:

Accepted Answer

A) 5.5 × 1013 
B) 6.5 × 1013 
C) 7.5 × 1013 
D) 8.5 × 1013 
E) 9.5 × 1013 
A) 5.5 × 1013 
B) 6.5 × 1013 
C) 7.5 × 1013 
D) 8.5 × 1013 
E) 9.5 × 1013

Question 17

The more closely electric field lines are packed together,the stronger the field.

Accepted Answer

A) True 
 B)False

Question 18

A point charge Q = - 400 nC and two unknown point charges,q1 and q2,are placed as shown.The electric field at the origin O,due to charges Q,q1 and q2,is equal to zero.In the figure,the number of excess electrons in charge Q,is closest to:

Accepted Answer

A) 2.5 × 102 
B) 1.4 × 102 
C) 2.9 × 102 
D) -1.4 × 102 
E) -2.5 × 102 
A) 2.5 × 102 
B) 1.4 × 102 
C) 2.9 × 102 
D) -1.4 × 102 
E) -2.5 × 102

Question 19

The charge in the bottom right corner of the figure is Q =- 45 nC.What is the magnitude of the force on Q?

Accepted Answer

A) 1.9 × 10-2 N 
B) 1.4 × 10-2 N 
C) 2.6 × 10-2 N 
D) 3.5 × 10-2 N 
A) 1.9 × 10-2 N 
B) 1.4 × 10-2 N 
C) 2.6 × 10-2 N 
D) 3.5 × 10-2 N

Question 20

Two identical small charged spheres are a certain distance apart,and each initially experiences an electrostatic force of magnitude F due to the other.With time,charge gradually diminishes on both spheres.When each of the spheres has lost half its initial charge,the magnitude of the electrostatic force will be:

Accepted Answer

A) 1/16 F. 
B) 1/8 F. 
C) 1/4 F. 
D) 1/2 F. 
A) 1/16 F. 
B) 1/8 F. 
C) 1/4 F. 
D) 1/2 F.

Exam 20: Electric Fields and Forces

The reaction 8p+ + 6e- → 2p+ violates charge conservation because there are more charges before the reaction than afterwards.

A 3.0 μC positive charge is located at the origin and a 2.0 μC positive charge is located at x = 0.0 m,y = 1.0 m.Find the point between them where the electric field strength is zero.

What is the strength of an electric field that a 0.010 C negative charge experiences 0.90 mm from a 0.20 C positive charge? (The value of K is 9.0 × 109 N·m2/C2. )

Two electrons are passing 26.0 mm apart.What is the electric repulsive force that they exert on each other? (The value of k is 9.0 × 109 N·m2/C2. )

The figure shows two 5.0 g spheres suspended from 1.0-m-long threads.The spheres repel each other after being charged to +91 nC.What is the angle θ?

The diagram shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: i.The charge on P is smaller than the charge on Q. Ii.The electrostatic force on P is smaller than that on Q. Which of the above statements are true?

If you rub a balloon on your sweater and then press it to a wall,it will often stick there.Why does this happen?

It is impossible for any object to have a charge of 7.5 e.

An electron is initially moving to the right when it enters a uniform electric field directed upwards.Which trajectory shown below will the electron follow?

If two macroscopic objects are electrically attracted to each other,

In the figure Q = 5.8 nC and all other quantities are exact.What is the magnitude of the force on the charge Q?

The electric field 2.8 cm from a small object points toward the object with a strength of 180,000 N/C.What is the object's charge?

Three point charges are at the vertices of an equilateral triangle.If the electric field at the midpoint of any side of this triangle points perpendicular to that side away from the inside of the triangle,you can conclude that these three charges have the same amount of charge and are all negative.

If the electric field strength produced by a point charge is 1000 N/C at 5.0 cm from this charge,the strength will be 25,000 N/C at a point 1.0 cm closer to this charge.

Two uncharged metal spheres,#1 and #2,are mounted on insulating support rods.A third metal sphere,carrying a positive charge,is then placed near #2.Now a copper wire is momentarily connected between #1 and #2 and then removed.Finally,sphere #3 is removed.In this final state

-A point charge Q = -12 μC,and two other charges,q1 and q2,are placed as shown.The electric force components on charge Q are Fx = +0.005 N and Fy = -0.003 N.In the figure,the number of excess electrons in charge Q is closest to:

The more closely electric field lines are packed together,the stronger the field.

A point charge Q = - 400 nC and two unknown point charges,q1 and q2,are placed as shown.The electric field at the origin O,due to charges Q,q1 and q2,is equal to zero.In the figure,the number of excess electrons in charge Q,is closest to:

The charge in the bottom right corner of the figure is Q =- 45 nC.What is the magnitude of the force on Q?

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What is the strength of an electric field that a 0.010 C negative charge experiences 0.90 mm from a 0.20 C positive charge? (The value of K is 9.0 × 10⁹ N·m²/C². )

Two electrons are passing 26.0 mm apart.What is the electric repulsive force that they exert on each other? (The value of k is 9.0 × 10⁹ N·m²/C². )

-A point charge Q = -12 μC,and two other charges,q₁ and q₂,are placed as shown.The electric force components on charge Q are F_x = +0.005 N and F_y = -0.003 N.In the figure,the number of excess electrons in charge Q is closest to:

A point charge Q = - 400 nC and two unknown point charges,q₁ and q₂,are placed as shown.The electric field at the origin O,due to charges Q,q₁ and q₂,is equal to zero.In the figure,the number of excess electrons in charge Q,is closest to: