Question 1

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

Accepted Answer

The answer of A particle (m = 20 mg, q...

Question 2

Charge Q is uniformly distributed over a line segment of length 2L, as shown below. When the x-coordinate of point P is x, the magnitude of the y-component of the electric field at point P is 
A) 0.
B)
 .
C)
 .
D)
 .
E)
 .

Accepted Answer

The answer of Charge Q is uniformly distributed over a...

Question 3

Two tiny metal spheres are fixed to the ends of a non-conducting string of length  . Equal charges, +q, are placed on the metal spheres. Randall says that the force on the string has magnitude  . Tilden says that the tension in the string has magnitude  . Which one, if either, is correct?
A) Randall, because both charges exert forces on the string, but the tension is
 .
B) Tilden, because both charges exert forces on the string, but the net force is
 .
C) Both are correct, because both charges exert forces on the string.
D) Neither is correct, because both the tension and the force have magnitude
 .
E) Neither is correct, because the tension is
 , but the net force is 0.

Accepted Answer

The answer of Two tiny metal spheres are fixed to...

Question 4

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 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.

Accepted Answer

The answer of Three 2.50 μC charges are placed on...

Question 5

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

Accepted Answer

The answer of A particle (m = 20 mg, q...

Question 6

Two charged particles, Q₁ and Q₂, are a distance r apart with Q₂ = 5Q₁. Compare the forces they exert on one another when is the force Q₂ exerts on Q₁ and is the force Q₁ exerts on Q₂. A) = 5 . B) = −5 . C) = . D) = − . E) 5 = .

Accepted Answer

The answer of Two charged particles, Q₁ and Q₂, are...

Question 7

When a positive charge q is placed in the field created by two other charges Q₁ and Q₂, each a distance r away from q, the acceleration of q is A) in the direction of the charge Q₁ or Q₂ of smaller magnitude. B) in the direction of the charge Q₁ or Q₂ of greater magnitude. C) in the direction of the negative charge if Q₁ and Q₂ are of opposite sign. D) in the direction of the positive charge if Q₁ and Q₂ are of opposite sign. E) in a direction determined by the vector sum of the electric fields of Q₁ and Q₂.

Accepted Answer

The acceleration of q will be in the direction of the net electric field at its position, which is the vector sum of the electric fields created by the two charges Q₁ and Q₂. Therefore, the correct answer is E.

Question 8

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 force on any one of the charges is A) 1.88 × 10−². B) 3.25 × 10−². C) 3.73 × 10−². D) 6.50 × 10−². E) 7.50 × 10−².

Accepted Answer

The answer of Three 2.50 μC charges are placed on...

Question 9

Two imaginary spherical surfaces of radius R and 2R respectively surround a positive point charge Q located at the center of the concentric spheres. When compared to the number of field lines N₁ going through the sphere of radius R, the number of electric field lines N₂ going through the sphere of radius 2R is A) . B) . C) N₂ = N₁. D) N₂ = 2N₁. E) N₂ = 4N₁.

Accepted Answer

The answer of Two imaginary spherical surfaces of radius R...

Question 10

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 force on the knot at the center is A) 0. B) 3.75 × 10−². C) 5.63 × 10−². D) 6.50 × 10−². E) 7.50 × 10−².

Accepted Answer

The answer of Three 2.50 μC charges are placed on...

Question 11

Rubber rods charged by rubbing with cat fur repel each other. Glass rods charged by rubbing with silk repel each other. A rubber rod and a glass rod charged respectively as above attract each other. A possible explanation is that
A) Any two rubber rods charged this way have opposite charges on them.
B) Any two glass rods charged this way have opposite charges on them.
C) A rubber rod and a glass rod charged this way have opposite charges on them.
D) All rubber rods always have an excess of positive charge on them.
E) All glass rods always have an excess of negative charge on them.

Accepted Answer

Rubber and glass have different electron affinities, so when rubbed with different materials they acquire different charges. Rubber becomes negatively charged and glass positively charged. Since opposites attract, the rubber and glass rod attract each other.

Question 12

Enrico says that positive charge is created when you rub a glass rod with silk, and that negative charge is simply the absence of positive charge. Rosetta says that negative charge is created and that positive charge is the absence of positive charge. (She has heard that Ben Franklin should have reversed the signs he associated with the charges.) Which one, if either, is correct?
A) Enrico, because there really is only one kind of charge.
B) Rosetta, because there really is only one kind of charge.
C) Neither: although no charge is present originally, both types of charge are created through friction.
D) Both: only one type of charge is created by friction at any one time.
E) Neither: both negative and positive charge are present simultaneously in all solid materials on Earth and the process described involves a transfer of charge, not the creation of charge.

Accepted Answer

When a glass rod is rubbed with silk, electrons (which carry negative charge) are transferred from one material to the other. This does not create charge but redistributes it, leaving one object positively charged (due to a deficit of electrons) and the other negatively charged (due to an excess of electrons). Both positive and negative charges are inherent in materials; the process of rubbing merely separates them.

Question 13

A negatively charged particle is moving in the +x-direction when it enters a region with a uniform electric field pointing in the +x-direction. Which graph gives its position as a function of time correctly? (Its initial position is x = 0 at t = 0.)
A)

B)

C)

D)

E)

Accepted Answer

The answer of A negatively charged particle is moving in...

Question 14

Two identical pith balls supported by insulating threads hang side by side and close together, as shown below.  One is positively charged; the other is neutral. We can conclude that
A) all field lines leaving the positively charged pith ball end on the neutral pith ball.
B) some of the field lines leaving the positively charged pith ball end on the neutral pith ball.
C) none of the field lines leaving the positively charged pith ball end on the neutral pith ball.
D) positive charge is transferred along the field lines until both balls have equal charges.
E) positive charge is transferred along the field lines until both balls hang along vertical lines.

Accepted Answer

The positively charged pith ball will create an electric field which will induce a separation of charge on the neutral pith ball, causing some negative charge to be attracted towards the positively charged pith ball and some positive charge to be repelled towards the far end of the neutral pith ball. As a result, some of the field lines leaving the positively charged pith ball will end on the neutral pith ball. However, not all field lines will end on the neutral pith ball since there is no conducting path for the charges to flow along the insulating threads.

Question 15

Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that
A) Y has a negative charge.
B) Z has a negative charge.
C) Y has a positive charge.
D) Z is neutral (has no net charge.)
E) Y is negatively charged or neutral (has no net charge.)

Accepted Answer

The answer of Three pith balls supported by insulating threads...

Question 16

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

B)

C)

D)

E)

Accepted Answer

The electric field lines in diagram D form closed loops, which would indicate the presence of a charge within the region. However, the prompt states that the region does not contain any charges, so this configuration is not possible. The other diagrams show electric field lines that do not form closed loops, which is consistent with the absence of any charges within the region.

Question 17

Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that
A) Y has a negative charge.
B) Z has a negative charge.
C) Y has a positive charge.
D) Z has a positive charge.
E) Z is neutral (has no net charge.)

Accepted Answer

The answer of Three pith balls supported by insulating threads...

Question 18

The symbol  appears in Coulomb's law because we use independently defined units for
A) force and distance.
B) charge and distance.
C) distance and force.
D) force, distance and electric charge.
E) charge.

Accepted Answer

The answer of The symbol  appears in Coulomb's law...

Question 19

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) 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.

Accepted Answer

Electric field lines represent the direction in which a positive test charge would accelerate if placed in the field, regardless of whether the charge is moving or static. This is because the electric field at a point in space defines the force per unit charge at that point, and the direction of this force (and thus acceleration) is tangent to the field lines at any given point.

Question 20

A positively charged particle is moving in the +y-direction when it enters a region with a uniform electric field pointing in the +x-direction. Which of the diagrams below shows its path while it is in the region where the electric field exists. The region with the field is the region between the plates bounding each figure. The field lines always point to the right. The x-direction is to the right; the y-direction is up.
A)

B)

C)

D)

E)

Accepted Answer

The answer of A positively charged particle is moving in...

Quiz 23: Electric Fields

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?

Charge Q is uniformly distributed over a line segment of length 2L, as shown below. When the x-coordinate of point P is x, the magnitude of the y-component of the electric field at point P is

Two tiny metal spheres are fixed to the ends of a non-conducting string of length . Equal charges, +q, are placed on the metal spheres. Randall says that the force on the string has magnitude . Tilden says that the tension in the string has magnitude . Which one, if either, is correct?

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

Two charged particles, Q1 and Q2, are a distance r apart with Q2 = 5Q1. Compare the forces they exert on one another when is the force Q2 exerts on Q1 and is the force Q1 exerts on Q2.

When a positive charge q is placed in the field created by two other charges Q1 and Q2, each a distance r away from q, the acceleration of q is

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 force on any one of the charges is

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 force on the knot at the center is

Rubber rods charged by rubbing with cat fur repel each other. Glass rods charged by rubbing with silk repel each other. A rubber rod and a glass rod charged respectively as above attract each other. A possible explanation is that

A negatively charged particle is moving in the +x-direction when it enters a region with a uniform electric field pointing in the +x-direction. Which graph gives its position as a function of time correctly? (Its initial position is x = 0 at t = 0.)

Two identical pith balls supported by insulating threads hang side by side and close together, as shown below. One is positively charged; the other is neutral. We can conclude that

Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that

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

Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that

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

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

Two charged particles, Q₁ and Q₂, are a distance r apart with Q₂ = 5Q₁. Compare the forces they exert on one another when is the force Q₂ exerts on Q₁ and is the force Q₁ exerts on Q₂.

When a positive charge q is placed in the field created by two other charges Q₁ and Q₂, each a distance r away from q, the acceleration of q is