Deck 16: Electric Forces and Fields

Question 1

When rubbing two insulators together, the one that gets a positive charge has had

A) protons added.
B) protons removed.
C) electrons added.
D) electrons removed.
E) electrons added, and protons removed.

Answer 1

electrons removed.

Question 2

When an object is polarized, it

A) must contain more positive charge than negative charge.
B) must contain more negative charge than positive charge.
C) will have a separation of positive and negative charge.
D) must be illuminated by polarized light.
E) must be made of metal.

Answer 2

will have a separation of positive and negative charge.

Question 3

The word electric comes from the Greek word for

A) wool.
B) amber.
C) silk.
D) glass.
E) lodestone.

Answer 3

amber.

Question 4

The Coulomb constant k has a value of 8.99 × 10⁹ N·m²/C². The permittivity of vacuum ε_o has the units

A) N·m²/C².
B) N·m/C.
C) C/(N·m).
D) C²/(N·m²).
E) none of the choices are correct.

Question 5

Three point charges are located on the x-axis. The first charge, q₁ = 10.0 µC, is at x = −1.00 m; the second charge, q₂ = 20.0 µC, is at the origin; and the third charge, q₃ = −30.0 µC, is located at x = 2.00 m. What is the force on q₂?

A) 1.65 N in the negative x-direction
B) 3.15 N in the positive x-direction
C) 1.50 N in the negative x-direction
D) 4.80 N in the positive x-direction
E) 4.65 N in the negative x-direction

Question 6

Three point charges are located on the x-axis. The first charge, q₁ = 10.0 µC, is at x = −1.00 m; the second charge, q₂ = 20.0 µC, is at the origin; and the third charge, q₃ = −30.0 µC, is located at x = 2.00 m. Which charge is subjected to the force of greatest magnitude?

A) q₁
B) q₂
C) q₃
D) q₁ and q₂ (equal)
E) q₂ and q₃ (equal)

Question 7

Two equal point charges are separated by a distance d. When the separation is reduced to d/4, what happens to the force between the charges?

A) it decreases by a factor of 4
B) it increases by a factor of 4
C) it increases by a factor of 8
D) it increases by a factor of 16
E) it increases by a factor of more than 16

Question 8

Two charges are separated by a distance d. If one the charges is doubled while the other is tripled, what happens to the force between the charges?

A) it increases by a factor of 5
B) it increases by a factor of 6
C) it increases by a factor of 12
D) it increases by a factor of 18
E) it increases by a factor of 36

Question 9

Pure water is classified as

A) an insulator.
B) a conductor.
C) a semiconductor.
D) all of these choices are correct
E) none of these choices are correct

Question 10

Arrange the following from smallest to largest.

A) mC, µC, nC, pC
B) µC, mC, pC, nC
C) nC, pC, mC, µC
D) pC, nC, µC, mC
E) nC, pC, µC, mC

Question 11

Two point charges are on the x-axis. One charge, q₁ = 10.0 nC, is located at the origin, and the other charge, q₂ = 18.0 nC, is located at x = 9.00 m. What is the force on q₂?

A) 20.0 nN in the positive x-direction
B) 20.0 pN in the positive x-direction
C) 20.0 nN in the negative x-direction
D) 20.0 pN in the negative x-direction
E) 180 nN in the positive x-direction

Question 12

If a neutral metal object has been charged by friction to a charge of one pC, what has happened to it electrically?

A) 6.25 × 10⁶ electrons have been added to it
B) 6.25 × 10⁶ protons have been added to it
C) 6.25 × 10⁶ electrons have been removed from it
D) 6.25 × 10⁶ protons have been removed from it
E) 6.25 × 10⁶ electrons and protons have been added to it

Question 13

Three point charges are located on the x-axis. The first charge, q₁ = 10.0 µC, is at x = −1.00 m; the second charge, q₂ = 20.0 µC, is at the origin; and the third charge, q₃ = −30.0 µC, is located at x = 2.00 m. What is the force on q₃?

A) 1.65 N in the negative x-direction
B) 3.15 N in the positive x-direction
C) 1.50 N in the negative x-direction
D) 4.80 N in the positive x-direction
E) 4.65 N in the negative x-direction

Question 14

Household wiring is made with

A) conductors inside insulators.
B) insulators inside conductors.
C) semiconductors inside conductors.
D) semiconductors inside insulators.
E) semiconductors inside insulators inside conductors.

Question 15

How many electrons does it take to make one coulomb of negative charge?

A) 1.00 × 10⁹
B) 6.24 × 10¹⁸
C) 6.02 × 10²³
D) 1.66 × 10¹⁸
E) 2.24 × 10⁴

Question 16

Three point charges are positioned as follows: q₁ is at (0.00 m, 0.00 m), q₂ is at (1.20 m, 0.00 m), and q₃ is at (1.20 m, 1.60 m). If all three charges are negative, into which quadrant is the force on q₁ pointing?

A) 1st
B) 2nd
C) 3rd
D) 4th
E) there isn't enough information in the problem to solve this

Question 17

Three point charges are positioned as follows: q₁ is at (0.00 m, 0.00 m), q₂ is at (1.20 m, 0.00 m), and q₃ is at (1.20 m, 1.60 m). If q₁ = 1.00 µC, q₂ = 2.00 µC, and q₃ = 3.00 µC, in what direction (ccw from the x-axis) is the force on q₂?

A) 301^°
B) 329^°
C) 149^°
D) 59.4^°
E) 39.1^°

Question 18

Some household appliances have plugs with two prongs while others have three prongs. The additional prong is

A) for direct current.
B) for 120-Hz voltage.
C) to connect to ground.
D) for additional mechanical strength.
E) for 240-Hz voltage.

Question 19

Three point charges are positioned as follows: q₁ is at (0.00 m, 0.00 m), q₂ is at (1.20 m, 0.00 m), and q₃ is at (1.20 m, 1.60 m). If q₁ = 1.00 µC, q₂ = 2.00 µC, and q₃ = 3.00 µC, what is the magnitude of the force on q₂?

A) 2.45 × 10^-2 N
B) 1.25 × 10^-2 N
C) 2.11 × 10^-2 N
D) 3.36 × 10^-2 N
E) 5.08 × 10^-2 N

Question 20

Three charges are located along a horizontal straight line. The charge on the left has a force of 6.00 N on it to the left. The charge in the middle has a force on it of 4.00 N to the right. What is the force on the charge on the right?

A) 2.00 N to the right
B) 10.0 N to the right
C) 10.0 N to the left
D) 24.0 N to the right
E) there isn't enough information in the problem to solve this

Question 21

The electron orbiting the proton in the hydrogen atom is at a distance of 5.3 × 10^-9 m. What is the magnitude of the electric force between the proton and the electron?

A) 1.6 × 10^-19 N
B) 2.7 × 10² N
C) 4.3 × 10^-17 N
D) 8.2 × 10^-12 N
E) 2.7 × 10^-2 N

Question 22

The electric field has a magnitude of 3.00 N/C at a distance of 60.0 cm from a point charge. What is the charge?

A) 1.40 nC
B) 120 pC
C) 36.0 mC
D) 12.0 µC
E) 3.00 nC

Question 23

The electron orbiting the proton in the hydrogen atom is at a distance of 5.3 × 10^-9 m. What is the ratio of the electric force to the gravitational force between these particles? (The mass of the proton is 1.67 × 10^-27 kg and the mass of the electron is 9.11 × 10^-31 kg.)

A) 2.3 × 10³⁹
B) 2.5 × 10²⁹
C) 1.7 × 10¹⁹
D) 9.0 × 10¹⁶
E) 3.00 × 10⁸

Question 24

Four point charges are located at the corners of a square, 1.00 m by 1.00 m. On each of two diagonally opposite corners are 1.00 µC charges. On each of the other two corners are −1.00 µC charges. What is the magnitude of the force on one of the positive charges?

A) 8.2 × 10^-3 N
B) 1.3 × 10^-2 N
C) 3.2 × 10^-3 N
D) 1.9 × 10^-2 N
E) 0.00

Question 25

A point charge of 3.00 µC is located on the y-axis at y = 4.0 m, another point charge of 6.0 µC is located on the x-axis at x = 5.0 m, and a third charge of 7.2 µC is located at (5.0 m, 4.0 m). What is the magnitude of the force on the 7.2 µC charge?

A) 1.2 × 10^-2 N
B) 1.6 × 10^-2 N
C) 1.9 × 10^-2 N
D) 2.5 × 10^-2 N
E) 3.3 × 10^-2 N

Question 26

A 3.7 pC charge experiences a force of 8.1 × 10^-7 N in an electric field. What is the magnitude of the electric field?

A) 3.00 × 10⁵ N/C
B) 2.2 × 10⁵ N/C
C) 4.3 × 10^-6 N/C
D) 12 N/C
E) 1.2 × 10^-3 N/C

Question 27

Four point charges are located at the corners of a square, 1.00 m by 1.00 m. On each of two diagonally opposite corners are 1.00 µC charges. On each of the other two corners are −1.00 µC charges. What is the direction of the force on each charge?

A) positive charges away from away from the center of the square, negative inward toward the center
B) negative charges away from away from the center of the square, positive inward toward the center
C) positive and negative charges both toward the center of the square
D) positive and negative charges both away from the center of the square
E) no direction (net force on each charge = 0)

Question 28

In a diagram of electric field lines, what is represented by lines that are drawn closer together?

A) a more positive field
B) a more negative field
C) a stronger field
D) a weaker field
E) nothing (artistic license)

Question 29

Two charges are located on the x-axis. A 22 µC charge is located at the origin and a 47 µC charge is located at x = 4.0 m. What is the magnitude of the electric field at x = 7.5 m?

A) 4.0 × 10⁵ N/C
B) 3.8 × 10⁴ N/C
C) 5.7 × 10⁵ N/C
D) 6.3 × 10⁴ N/C
E) 2.5 × 10⁶ N/C

Question 30

What is the magnitude of the electric field 30.0 cm from a point charge of 0.35 µC?

A) 1.2 × 10^-2 N/C
B) 9.5 × 10^-4 N/C
C) 9.5 × 10⁴ N/C
D) 3.5 × 10⁴ N/C
E) 1.1 × 10⁴ N/C

Question 31

Two charges are located on the x-axis. A 22 µC charge is located at the origin and a 47 µC charge is located at x = 4.0 m. What is the electric field at x = 3.00 m?

A) 4.5 × 10⁵ N/C in the positive x-direction
B) 4.9 × 10⁵ N/C in the negative x-direction
C) 4.0 × 10⁵ N/C in the negative x-direction
D) 4.9 × 10⁵ N/C in the positive x-direction
E) 6.3 × 10⁵ N/C in the negative x-direction

Question 32

A 1.00 nC charge is placed on the x-axis at x = −1.00 m. A second 1.00 nC charge is placed on the x-axis at x = 1.00 m. A third charge of 1.00 nC is placed on the y-axis at y = −1.00 m. A fourth charge is place on the y-axis at y = 1.00 m. What is the fourth charge if the electric field at the origin is zero?

A) 1.00 nC
B) −1.00 nC
C) 3.00 nC
D) −3.00 nC
E) 2.00 nC

Question 33

An arrangement of 3 charges is drawn showing the field lines. The first charge has 20 lines going into it. The second charge has 30 lines going out of it. If the net charge of the arrangement is zero, what is the field line situation for the third charge?

A) 50 lines going out
B) 50 lines going in
C) 10 lines going out
D) 10 lines going in
E) 600 lines going out to infinity

Question 34

In a diagram of electric field lines, q₁ has 9 lines going into it and q₂ has 27 lines going out of it. If one of the charges is −40 mC, which of the following could be the other one?

A) −120 mC
B) 18.0 mC
C) −18.0 mC
D) 120 mC
E) none of these choices are correct

Question 35

A 72 nC charge is located at x = 3.00 m on the x-axis and an 8.0 nC charge is located at x = 7.0 m. At what point on the x-axis is the electric field zero?

A) −9.0 m
B) 4.0 m
C) −5.0 m
D) 6.0 m
E) 6.3 m

Question 36

A point charge of 3.0 µC is located on the y-axis at y = 4.0 m, and another point charge of 6.0 µC is located on the x-axis at x = 5.0 m. What is the magnitude of the electric field at the position (5.0 m, 4.0 m)?

A) 2.7 × 10³ N/C
B) 3.5 × 10³ N/C
C) 2.7 × 10^-3 N/C
D) 3.5 × 10^-3 N/C
E) 4.5 × 10³ N/C

Question 37

When the perpendicular distance from an infinitely long wire with a uniform linear charge distribution is tripled, what happens to the electric field strength?

A) it stays the same
B) it decreases by a factor of 3
C) it decreases by a factor of 9
D) it decreases by a factor of (3)^1/2
E) it increases by a factor of (3)^1/2

Question 38

A point charge of 3.0 µC is located on the y-axis at y = 4.0 m, and another point charge of 6.0 µC is located on the x-axis at x = 5.0 m. What is the direction (ccw from the x-axis) of the electric field at (5.0 m, 4.0 m)?

A) 72^°
B) 18^°
C) 25^°
D) 53^°
E) 34^°

Question 39

Two alpha particles (helium nuclei) are separated by 4.0 × 10^-15 m. What is the magnitude of the force between the particles due to their charge?

A) 6.8 × 10^-22 N
B) 4.5 × 10^-19 N
C) 1.1 × 10^-4 N
D) 14 N
E) 58 N

Question 40

Increasing the distance from a point charge by 34% changes the magnitude of the electric field by what amount?

A) it decreases by 16%
B) it decreases by 34%
C) it decreases by 44%
D) it decreases by 80%
E) it stays the same

Question 41

A thin metallic spherical shell of radius 50 cm has a total charge of 4.0 µC placed on it. At the center of the shell is placed a point charge of 2.00 µC. What is the electric field at a distance of 30.0 cm from the center of the spherical shell?

A) 6.0 × 10⁵ N/C outward
B) 2.0 × 10⁵ N/C outward
C) 4.0 × 10⁵ N/C inward
D) 4.0 × 10⁵ N/C outward
E) 0.0

Question 42

An electron gun sends electrons through a region with an electric field of magnitude 1.5 × 10⁴ N/C for a distance of 2.5 cm. What is the acceleration of the electrons while in this electric field?

A) 1.4 × 10⁸ m/s²
B) 2.6 × 10¹¹ m/s²
C) 1.4 × 10¹² m/s²
D) 2.6 × 10¹⁵ m/s²
E) 3.0 × 10⁸ m/s²

Question 43

A thin spherical shell of radius 20.0 cm has 5.0 µC of charge uniformly distributed over its surface. What is the magnitude of the electric field 2.00 m from the center of the sphere?

A) 2.3 × 10⁴ N/C
B) 1.1 × 10⁴ N/C
C) 1.4 × 10³ N/C
D) 2.3 × 10⁶ N/C
E) 0

Question 44

An electron is fired through the space between two oppositely charged, parallel plates. The plates form a 2.00 cm long region with an electric field of 4000 N/C perpendicular to the electron's initial velocity. If the initial speed of the electron is 1.00 × 10⁷ m/s, what angle will its new velocity make relative to the direction of the original velocity?

A) 14^°
B) 8.0^°
C) 5.5^°
D) 4.6^°
E) 1.4^°

Question 45

A thin spherical shell of radius 20.0 cm has 5.0 µC of charge uniformly distributed over its surface. What is the electric field 10.0 cm from the center of the sphere?

A) 4.5 × 10⁶ N/C inward
B) 4.5 × 10⁶ N/C outward
C) 2.3 × 10⁶ N/C inward
D) 2.3 × 10⁶ N/C outward
E) 0

Question 46

What is the magnitude of the acceleration of an electron when in an electric field of magnitude 7.0 × 10⁴ N/C?

A) 3.0 × 10⁸ m/s²
B) 1.2 × 10¹⁶ m/s²
C) 7.7 × 10³⁴ m/s²
D) 8.6 × 10²⁰ m/s²
E) 7.0 × 10⁴ m/s²

Question 47

A thin metallic shell of radius 40 cm has a charge of −25 nC on it. At the center of the sphere is a point charge of 35 nC. What is the electric field 50 cm from the center of the shell?

A) 400 N/C outward
B) 560 N/C outward
C) 360 N/C outward
D) 360 N/C inward
E) 560 N/C inward

Question 48

An infinitely long wire with a uniform linear charge distribution has a charge per unit length of 2.3 × 10^-6 C/m. What is the magnitude of the electric field at a perpendicular distance of 0.50 m from the wire?

A) 0.19 N/C
B) 0.38 N/C
C) 1.1 × 10² N/C
D) 1.7 × 10⁴ N/C
E) 8.3 × 10⁴ N/C

Question 49

For a conductor in electrostatic equilibrium, which of the following statements is NOT true?

A) The electric field inside the conductor is zero.
B) The charge distributes itself uniformly throughout the conductor.
C) The electric field at the surface of the conductor is perpendicular to the surface of the conductor.
D) The greatest concentrations of charge on the surface are in the regions of highest curvature.
E) More than one of these statements about a conductor in electrostatic equilibrium is false.

Question 50

An electron is fired through the space between two oppositely charged, parallel plates. The plates form a 2.00 cm long region with an electric field of 4000 N/C perpendicular to the electron's initial velocity. If the initial speed of the electron is 1.00 × 10⁷ m/s, how long does it take to traverse the plates?

A) 2.00 µs
B) 2.00 ns
C) 1.70 ns
D) 1.80 ns
E) 1.50 µs

Question 51

In an electron gun, electrons are accelerated through a region with an electric field of magnitude 1.5 × 10⁴ N/C for a distance of 2.5 cm. If the electrons start from rest, how fast are they moving after traversing the gun?

A) 1.1 × 10⁴ m/s
B) 1.1 × 10⁷ m/s
C) 2.3 × 10⁴ m/s
D) 2.3 × 10⁷ m/s
E) 2.6 × 10¹⁵ m/s

Question 52

In an electron gun, electrons are accelerated through a region with an electric field of magnitude 1.5 × 10⁴ N/C for a distance of 2.5 cm. If the electrons start from rest, how long does it take for the electrons to traverse the gun?

A) 1.1 ns
B) 1.1 µs
C) 2.2 ns
D) 2.2 µs
E) 4.4 ns

Question 53

If more field lines leave a closed surface than enter that surface, then

A) a net positive charge is contained inside the surface.
B) a net negative charge is contained inside the surface.
C) an error has been made since the number of field lines entering a surface must equal those leaving the surface.
D) an operating electron gun is inside the surface.
E) there must be a charge on the surface.

Question 54

A thin metallic spherical shell of radius 50 cm has a total charge of 4.0 µC placed on it. At the center of the shell is placed a point charge of 2.00 µC. What is the electric field at a distance of 90 cm from the center of the spherical shell?

A) 4.4 × 10⁴ N/C outward
B) 2.7 × 10³ N/C inward
C) 6.7 × 10⁴ N/C outward
D) 8.8 × 10⁴ N/C outward
E) 6.7 × 10⁴ N/C inward

Question 55

A conducting sphere of radius 10.0 cm holds a net charge of 4.4 µC. What is the surface charge density?

A) 0.0
B) 3.5 × 10^-5 C/m²
C) 1.1 × 10^-5 C/m²
D) 2.2 × 10^-4 C/m²
E) 5.6 × 10^-3 C/m²

Question 56

A thin metallic shell of radius 40 cm has a charge of −25 nC on it. At the center of the sphere is a point charge of 35 nC. What is the electric field 15 cm from the center of the shell?

A) 2.4 × 10⁴ N/C inward
B) 1.4 × 10⁴ N/C inward
C) 2.4 × 10⁴ N/C outward
D) 1.4 × 10⁴ N/C outward
E) 4.0 × 10⁴ N/C outward

Question 57

An electron is fired through the space between two oppositely charged, parallel plates. The plates form a 2.00 cm long region with an electric field of 4000 N/C perpendicular to the electron's initial velocity. What is the change in velocity of the electron after it passes through the plates?

A) 2.0 × 10⁷ m/s
B) 7.1 × 10⁶ m/s
C) 2.8 × 10⁶ m/s
D) 1.4 × 10⁶ m/s
E) 6.5 × 10⁴ m/s

Question 58

A long wire with uniform linear charge density 1.35 nC/m is surrounded by a concentric cylindrical surface of length 1.60 m and radius 23.6 cm. What is the magnitude of the electric field at the curved surface of the cylinder?

A) 436 N/C
B) 103 N/C
C) 51.5 N/C
D) 135 N/C
E) 0.0

Question 59

A proton is moving in an electric field. The direction of the acceleration of the proton is

A) in the direction the proton is moving.
B) opposite the direction the proton is moving.
C) perpendicular to the direction the proton is moving.
D) in the direction of the electric field.
E) opposite the direction of the electric field.

Question 60

A 1.65 nC charge experiences an acceleration of 6.33 × 10⁷ m/s² in an electric field. What is the magnitude of the electric field?

A) 3.84 × 10¹⁶ N/C
B) 1.65 × 10^-9 N/C
C) 14.9 N/C
D) 2.67 × 10^-19 N/C
E) there isn't enough information in the problem to solve this

Question 61

Each atom in a sample of lithium (Z = 3, atomic mass 6.941 u) has all of its electrons removed. If a charge of magnitude 1.0 mC was collected in this way, what is the mass of the lithium sample?

A) 0.010 µg
B) 0.024 µg
C) 0.031 µg
D) 0.072 µg

Question 62

Each atom in a mole of water vapor (H₂O) has one electron removed. What is the total charge of the ionized gas?

A) 96 kC
B) 290 kC
C) 600 kC
D) 190 kC

Question 63

An electric dipole is surrounded by a closed surface with the surface nearer to the negative end of the dipole than the positive end. The flux through the surface is

A) positive.
B) negative.
C) proportional to the negative charge.
D) inversely proportional to the positive charge.
E) zero.

Question 64

Each atom in a sample of lithium (Z=3, atomic mass 6.941u) has one electron removed. If a charge of magnitude 1.0 mC was collected in this way, what is the mass of the lithium sample?

A) 0.024 µg
B) 0.010 µg
C) 0.031 µg
D) 0.072 µg

Question 65

Electric field lines symbolize

A) the force a positive charge would experience at the location of the line.
B) the path a positive charge would take if released from rest on one of the lines.
C) the distribution of electric charges in space.
D) boundaries between regions of positive and negative charge.

Question 66

A horizontally projected beam of protons travels at 55 km/s into the space between two horizontal, parallel plates. The plates are separated by 7.4 cm, and they are 12 cm long. There is a uniform electric field between the plates of unknown strength. The beam enters the region exactly midway (vertically) between the plates and exits the region 7.2 microns closer to the lower plate. If it were a beam of electrons instead, everything else being the same, at what height above the lower plate would the beam exit the region between the plates? The proton mass is 1.67 × 10^-27 kg, and electron mass is 9.11 × 10^-31 kg.

A) 0.9 cm
B) 5.0 cm
C) 2.3 cm
D) 4.6 cm

Question 67

A thin spherical shell of radius 20.0 cm has 5.0 µC of charge uniformly distributed over its surface. What is the electric flux through an area of 1.00 m² of a spherical surface concentric with the shell of charge but having a radius of 1.00 m?

A) 5.6 × 10⁵ N·m²/C
B) 4.5 × 10⁴ N·m²/C
C) 1.8 × 10⁴ N·m²/C
D) 2.3 × 10⁵ N·m²/C
E) 0

Question 68

A spherical conducting shell has a uniform surface charge density of 1.5 × 10^-7 C/m². What is its radius if the electric field 1.5 m from its center is 17 N/C outward?

A) 3.9 cm
B) 4.8 cm
C) 3.2 cm
D) 9.5 cm
E) 6.4 cm

Question 69

Electrons are collected by removing them from the atoms in a sample of water vapor (H₂O, molecular mass 18 u). If every hydrogen atom has lost an electron in the process, what is the mass of the sample if a charge of magnitude 1.0 C was collected?

A) 62 µg
B) 370 µg
C) 93 µg
D) 180 µg

Question 70

A long linear charge distribution of uniform charge density 1.35 nC/m is surrounded by a concentric cylindrical surface of length 1.60 m and radius 23.6 cm. What is the electric flux through the surface of the cylinder?

A) 0.00
B) 160 N·m²/C
C) 244 N·m²/C
D) 280 N·m²/C
E) 316 N·m²/C

Question 71

We find from Gauss's law that the flux through a closed surface

A) is proportional to the net charge enclosed.
B) is inversely proportional to the net charge enclosed.
C) is proportional to the square root of the charge enclosed.
D) is zero.
E) is less the larger the closed surface.

Question 72

A charged metal sphere has a mass of 15 µg and a net charge of −1.5 mC. What vertical electric field would cause this sphere, if projected horizontally, to continue in a straight line?

A) 98 µV/m downward
B) 10 mV/m upward
C) 10 mV/m downward
D) 98 µV/m upward

Question 73

A horizontally projected beam of electrons travels at 55 km/s into the space between two horizontal, parallel plates. The plates are separated by 7.4 cm, and they are 12 cm long. The uniform electric field between the plates is 7.2 mV/m upward. If the beam enters the region at a height of 3.7 cm above the lower plate, at what height above the lower plate does the beam exit the region? The electron mass is 9.11 × 10^-31 kg.

A) 0.9 cm
B) 2.3 cm
C) 3.4 cm
D) 4.6 cm

Question 74

A cylinder contains a charge Q. The flux through the curved side of the container is 3πkQ. What is the flux through the ends of the cylinder?

A) 3π kQ
B) 5π kQ
C) 9π kQ
D) π kQ
E) 0.0

Question 75

A horizontally projected beam of electrons travels at 55 km/s into the space between two horizontal, parallel plates. The beam travels exactly horizontally the whole time it is between the plates. What does this imply about the electric field between the plates?

A) It is 0.
B) It is 56 pV/m upward.
C) It is 56 pV/m downward.
D) It doesn't imply anything in particular.

Question 76

The electric field between two oppositely charged, parallel, conducting plates is

A) zero.
B) strongest near the negative plate.
C) strongest near the positive plate.
D) approximately uniform.

Question 77

The symbols ρ, λ, and σ are used to represent, respectively, the charge density per unit

A) length, volume, and area.
B) volume, length, and area.
C) area, volume, and length.
D) volume, area, and length.
E) area, length, and volume.

Question 78

What is the total electric flux through a closed surface containing a 2.0 µC charge?

A) 1.8 × 10⁴ N·m²/C
B) 2.3 × 10⁵ N·m²/C
C) 1.4 × 10⁵ N·m²/C
D) 4.5 × 10³ N·m²/C
E) 0

Question 79

Each atom in a 7.0 microgram piece of calcium (A=40, Z=20) has one electron removed. What is the magnitude of the total charge collected in this way?

A) 34 mC
B) 670 mC
C) 17 mC
D) 60 mC

Question 80

A horizontally projected beam of protons travels at 55 km/s into the space between two horizontal, parallel plates. The plates are separated by 7.4 cm, and they are 12 cm long. The uniform electric field between the plates is 7.2 V/m upward. If the beam enters the region at a height of 3.7 cm above the lower plate, at what height above the lower plate does the beam exit the region? The proton mass is 1.67 × 10^-27 kg.

A) 4.4 cm
B) 3.9 cm
C) 5.1 cm
D) 2.3 cm