Question 1

If a = 60 cm,b = 80 cm,Q = −4.0 nC,and q = 1.5 nC,what is the magnitude of the electric field at point P?

Accepted Answer

A) 68 N/C 
B) 72 N/C 
C) 77 N/C 
D) 82 N/C 
E) 120 N/C 
A) 68 N/C 
B) 72 N/C 
C) 77 N/C 
D) 82 N/C 
E) 120 N/C

Question 2

Which one of the diagrams below is not a possible electric field configuration for a region of space which does not contain any charges?

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Question 3

Each of two small non-conducting spheres is charged positively,the combined charge being 40 μC.When the two spheres are 50 cm apart,each sphere is repelled from the other by a force of magnitude 2.0 N.Determine the magnitude of the smaller of the two charges.

Accepted Answer

A) 1.4 μC 
B) 1.1 μC 
C) 2.0 μC 
D) 3.3 μC 
E) 17 μC 
A) 1.4 μC 
B) 1.1 μC 
C) 2.0 μC 
D) 3.3 μC 
E) 17 μC

Question 4

The symbol  
Appears in Coulomb's law because we use independently defined units for

Accepted Answer

A) force and distance. 
B) charge and distance. 
C) distance and force. 
D) force,distance and electric charge. 
E) charge. 
A) force and distance. 
B) charge and distance. 
C) distance and force. 
D) force,distance and electric charge. 
E) charge.

Question 5

Two uniform rods,each of length 2.0 m,are bent to form semicircles.One rod has a charger per unit lent of 1.5 nC/m,and the other has a charge per unit length of -1.5 nC/m.The semicircles are joined to make a circle.What is the magnitude of the electric field at the center of the circle?

Accepted Answer

A) 42 N/C 
B) 84 N/C 
C) 34 N/C 
D) 68 N/C 
E) 0 
A) 42 N/C 
B) 84 N/C 
C) 34 N/C 
D) 68 N/C 
E) 0

Question 6

A +2.0-nC point charge is placed at one corner of a square (1.5 m on a side),and a −3.0-nC charge is placed on a corner diagonally away from the first charge.What is the magnitude of the electric field at either of the two unoccupied corners?

Accepted Answer

A) 20 N/C 
B) 14 N/C 
C) 4.0 N/C 
D) 12 N/C 
E) 8.0 N/C 
A) 20 N/C 
B) 14 N/C 
C) 4.0 N/C 
D) 12 N/C 
E) 8.0 N/C

Question 7

If Q = 16 nC,a = 3.0 m,and b = 4.0 m,what is the magnitude of the electric field at point P?

Accepted Answer

A) 33 N/C 
B) 31 N/C 
C) 24 N/C 
D) 19 N/C 
E) 13 N/C 
A) 33 N/C 
B) 31 N/C 
C) 24 N/C 
D) 19 N/C 
E) 13 N/C

Question 8

A particle (m = 20 mg,q = −5.0 μC)moves in a uniform electric field of 60 N/C in the positive x direction.At t = 0,the particle is moving 25 m/s in the positive x direction and is passing through the origin.How far is the particle from the origin at t = 2.0 s?

Accepted Answer

A) 80 m 
B) 20 m 
C) 58 m 
D) 10 m 
E) 30 m 
A) 80 m 
B) 20 m 
C) 58 m 
D) 10 m 
E) 30 m

Question 9

Three 2.50 μC charges are placed on tiny conducting spheres at the ends of 1.00 m-long strings that are connected at 120° angles as shown below.The magnitude,in N,of the tension in any one of the strings is

Accepted Answer

A) 1.88 × 10−2. 
B) 3.25 × 10−2. 
C) 3.75 × 10−2. 
D) 6.50 × 10−2. 
E) 7.50 × 10−2. 
A) 1.88 × 10−2. 
B) 3.25 × 10−2. 
C) 3.75 × 10−2. 
D) 6.50 × 10−2. 
E) 7.50 × 10−2.

Question 10

Imagine for a minute that the Moon is held in its orbit about the Earth by electrical forces rather than by gravitation.What electrical charges −Q on the Earth and +Q on the Moon are necessary to hold the Moon in a circular orbit with a period of 27.3 days? The Earth-Moon distance is 384 000 km and the mass of the Moon is 7.35 × 1022 kg.

Accepted Answer

Question 11

Suppose a uniform electric field of 4 N/C is in the positive x direction.When a charge is placed at and fixed to the origin,the resulting electric field on the x axis at x = 2 m becomes zero.What is the magnitude of the electric field at x = 4 m on the x axis at this time?

Accepted Answer

A) 0 
B) 1 N/C 
C) 2 N/C 
D) 4 N/C 
E) More information is needed to find the resulting field magnitude at this position. 
A) 0 
B) 1 N/C 
C) 2 N/C 
D) 4 N/C 
E) More information is needed to find the resulting field magnitude at this position.

Question 12

A point charge Q is placed on the x axis at x = −2.0 m.A second point charge,−Q,is placed at x = 1.0 m.If Q = 60 μC,what is the magnitude of the electrostatic force on a 40-μC charge placed at the origin?

Accepted Answer

A) 16 N 
B) 27 N 
C) 32 N 
D) 11 N 
E) 3.0 N 
A) 16 N 
B) 27 N 
C) 32 N 
D) 11 N 
E) 3.0 N

Question 13

A particle (m = 20 mg,q = −5.0 μC)moves in a uniform electric field of 60 N/C in the positive x direction.At t = 0,the particle is moving 30 m/s in the positive x direction and is passing through the origin.Determine the maximum distance beyond x = 0 the particle travels in the positive x direction.

Accepted Answer

A) 25 m 
B) 20 m 
C) 15 m 
D) 30 m 
E) 60 m 
A) 25 m 
B) 20 m 
C) 15 m 
D) 30 m 
E) 60 m

Question 14

A 16-nC charge is distributed uniformly along the x axis from x = 0 to x = 4 m.Which of the following integrals is correct for the magnitude (in N/C)of the electric field at x = +10 m on the x axis?

Accepted Answer

A)    
B)    
C)    
D)    
E) none of these 
A)    
B)    
C)    
D)    
E) none of these

Question 15

The electron gun in a television tube accelerates electrons (mass = 9.11 × 10−31 kg,charge = 1.60 × 10−19 C)from rest to 3.00 × 107 m/s within a distance of 2.00 cm.What electric field is required?

Accepted Answer

Question 16

When gravitational,magnetic and any forces other than static electric forces are not present,electric field lines in the space surrounding a charge distribution show

Accepted Answer

A) the directions of the forces that exist in space at all times. 
B) only the directions in which static charges would accelerate when at points on those lines 
C) only the directions in which moving charges would accelerate when at points on those lines. 
D) tangents to the directions in which either static or moving charges would accelerate when passing through points on those lines. 
E) the paths static or moving charges would take. 
A) the directions of the forces that exist in space at all times. 
B) only the directions in which static charges would accelerate when at points on those lines 
C) only the directions in which moving charges would accelerate when at points on those lines. 
D) tangents to the directions in which either static or moving charges would accelerate when passing through points on those lines. 
E) the paths static or moving charges would take.

Question 17

A proton moving at 3 × 104 m/s is projected at an angle of 30° above a horizontal plane.If an electric field of 400 N/C is directed downwards,how long does it take the proton to return to the horizontal plane? (HINT: Ignore gravity. )[mProton = 1.67 × 10−27 kg,qProton = +1.6 × 10−19 C.]

Accepted Answer

Question 18

A particle (mass = 5.0 g,charge = 40 mC)moves in a region of space where the electric field is uniform and is given by Ex = −2.3 N/C,Ey = Ez = 0.If the position and velocity of the particle at t = 0 are given by x = y = z = 0 and vz = 20 m/s,vx = vy = 0,what is the distance from the origin to the particle at t = 2.0 s?

Accepted Answer

A) 60 m 
B) 54 m 
C) 69 m 
D) 78 m 
E) 3.2 m 
A) 60 m 
B) 54 m 
C) 69 m 
D) 78 m 
E) 3.2 m

Question 19

A point charge Q is placed at the origin.A second charge,2Q,is placed on the x axis at x = −3.0 m.If Q = 50 μC,what is the magnitude of the electrostatic force on a third point charge,−Q,placed on the y axis at y = +4.0 m?

Accepted Answer

A) 2.5 N 
B) 3.0 N 
C) 3.7 N 
D) 4.4 N 
E) 1.8 N 
A) 2.5 N 
B) 3.0 N 
C) 3.7 N 
D) 4.4 N 
E) 1.8 N

Question 20

A particle (m = 50 g,q = 5.0 μC)is released from rest when it is 50 cm from a second particle (Q = −20 μC).Determine the magnitude of the initial acceleration of the 50-g particle.

Accepted Answer

A) 54 m/s2 
B) 90 m/s2 
C) 72 m/s2 
D) 65 m/s2 
E) 36 m/s2 
A) 54 m/s2 
B) 90 m/s2 
C) 72 m/s2 
D) 65 m/s2 
E) 36 m/s2

Exam 23: Electric Fields

If a = 60 cm,b = 80 cm,Q = −4.0 nC,and q = 1.5 nC,what is the magnitude of the electric field at point P?

Which one of the diagrams below is not a possible electric field configuration for a region of space which does not contain any charges?

Each of two small non-conducting spheres is charged positively,the combined charge being 40 μC.When the two spheres are 50 cm apart,each sphere is repelled from the other by a force of magnitude 2.0 N.Determine the magnitude of the smaller of the two charges.

The symbol Appears in Coulomb's law because we use independently defined units for

Two uniform rods,each of length 2.0 m,are bent to form semicircles.One rod has a charger per unit lent of 1.5 nC/m,and the other has a charge per unit length of -1.5 nC/m.The semicircles are joined to make a circle.What is the magnitude of the electric field at the center of the circle?

A +2.0-nC point charge is placed at one corner of a square (1.5 m on a side),and a −3.0-nC charge is placed on a corner diagonally away from the first charge.What is the magnitude of the electric field at either of the two unoccupied corners?

If Q = 16 nC,a = 3.0 m,and b = 4.0 m,what is the magnitude of the electric field at point P?

A particle (m = 20 mg,q = −5.0 μC)moves in a uniform electric field of 60 N/C in the positive x direction.At t = 0,the particle is moving 25 m/s in the positive x direction and is passing through the origin.How far is the particle from the origin at t = 2.0 s?

Three 2.50 μC charges are placed on tiny conducting spheres at the ends of 1.00 m-long strings that are connected at 120° angles as shown below.The magnitude,in N,of the tension in any one of the strings is

Suppose a uniform electric field of 4 N/C is in the positive x direction.When a charge is placed at and fixed to the origin,the resulting electric field on the x axis at x = 2 m becomes zero.What is the magnitude of the electric field at x = 4 m on the x axis at this time?

A point charge Q is placed on the x axis at x = −2.0 m.A second point charge,−Q,is placed at x = 1.0 m.If Q = 60 μC,what is the magnitude of the electrostatic force on a 40-μC charge placed at the origin?

A 16-nC charge is distributed uniformly along the x axis from x = 0 to x = 4 m.Which of the following integrals is correct for the magnitude (in N/C)of the electric field at x = +10 m on the x axis?

The electron gun in a television tube accelerates electrons (mass = 9.11 × 10−31 kg,charge = 1.60 × 10−19 C)from rest to 3.00 × 107 m/s within a distance of 2.00 cm.What electric field is required?

When gravitational,magnetic and any forces other than static electric forces are not present,electric field lines in the space surrounding a charge distribution show

A proton moving at 3 × 104 m/s is projected at an angle of 30° above a horizontal plane.If an electric field of 400 N/C is directed downwards,how long does it take the proton to return to the horizontal plane? (HINT: Ignore gravity. )[mProton = 1.67 × 10−27 kg,qProton = +1.6 × 10−19 C.]

A point charge Q is placed at the origin.A second charge,2Q,is placed on the x axis at x = −3.0 m.If Q = 50 μC,what is the magnitude of the electrostatic force on a third point charge,−Q,placed on the y axis at y = +4.0 m?

A particle (m = 50 g,q = 5.0 μC)is released from rest when it is 50 cm from a second particle (Q = −20 μC).Determine the magnitude of the initial acceleration of the 50-g particle.

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The electron gun in a television tube accelerates electrons (mass = 9.11 × 10−³¹ kg,charge = 1.60 × 10−¹⁹ C)from rest to 3.00 × 10⁷ m/s within a distance of 2.00 cm.What electric field is required?