Deck 16: The Electric Field

Question 1

The figure 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 exerted on P is smaller than the force exerted on Q.
Which of the above statements are true?

A)Only (i)is true.
B)Only (ii)is true.
C)Both (i)and (ii)are true.
D)Neither (i)nor (ii)is true.

Answer 1

A

Question 2

An electron is initially moving to the right when it enters a uniform electric field directed upwards,as shown in the figure.Which trajectory (X,Y,Z,or W)will the electron follow in the field?

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

Answer 2

D

Question 3

Which one of the arrows shown in the figure best represents the direction of the field between the two uniformly charged metal plates?

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

Answer 3

A

Question 4

A solid aluminum cube rests on a wooden table in a region where a uniform external electric field is directed straight upward.What can we say concerning the charge on the top surface of the cube?

A)The top surface is charged positively.
B)The top surface is charged negatively.
C)The top surface is neutral.
D)The top surface's charge cannot be determined without further information.

Question 5

Three equal negative point charges -q are placed at three of the corners of a square of side d as shown in the figure.Which one of the arrows shown represents the direction of the net field at the center of the square?

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

Question 6

As an electron moves in the direction the field lines

A)it is moving from the field's low potential to high potential and the electric potential energy of the system electron-electric field is increasing.
B)it is moving from the field's low potential to high potential and the electric potential energy of the system electron-electric field is decreasing.
C)it is moving from the field's high potential to low potential and the electric potential energy of the system electron-electric field is increasing.
D)it is moving from the field's high potential to low potential and the electric potential energy of the system electron-electric field is decreasing.
E)both the electric potential and electric potential energy of the system electron-electric field remain constant.

Question 7

Two stationary point charges q₁ and q₂ are shown in the figure along with a sketch of some field lines representing the electric field produced by them.What can you deduce from the sketch?

A)q₁ is negative and q₂ is positive; the magnitudes are equal.
B)q₁ and q₂ have the same sign; the magnitudes are equal.
C)q₁ is positive and q₂ is negative; the magnitude of q₁ is greater than the magnitude of q₂.
D)q₁ is negative and q₂ is positive; the magnitude of q₁ is less than the magnitude of q₂.
E)q₁ and q₂ have the same sign; the magnitude of q₁ is greater than the magnitude of q₂.

Question 8

If the electric potential at a point in space is zero,then the field at that point must be

A)negative.
B)zero.
C)uniform.
D)positive.
E)impossible to determine based on the information given.

Question 9

As a proton moves in the direction the field lines

A)it is moving from field's low potential to high potential and electric potential energy of the system proton-electric field is increasing.
B)it is moving from field's low potential to high potential and electric potential energy of the system proton-electric field is decreasing.
C)it is moving from field's high potential to low potential and electric potential energy of the system proton-electric field is increasing.
D)it is moving from field's high potential to low potential and electric potential energy of the system proton-electric field is decreasing.
E)both it's the electric potential and electric potential energy of the system proton-electric field remain constant.

Question 10

The field at point P due to a point charge Q a distance R away from P has magnitude E.In order to double the magnitude of the field at P,you could

A)double the distance to 2R.
B)double the charge to 2Q.
C)reduce the distance to R/2.
D)reduce the distance to R/4.
E)double the charge to 2Q and at the same time reduce the distance to R/2.

Question 11

As a proton moves in a direction perpendicular to the field lines

A)it is moving from the field's low potential to high potential and the electric potential energy of the system proton-electric field is increasing.
B)it is moving from the field's low potential to high potential and the electric potential energy of the system proton-electric field is decreasing.
C)it is moving from the field's high potential to low potential and the electric potential energy of the system proton-electric field is increasing.
D)it is moving from the field's high potential to low potential and the electric potential energy of the system proton-electric field is decreasing.
E)both the field's electric potential and electric potential energy of the system proton-electric field remain constant.

Question 12

A proton is accelerated from rest through a potential difference V₀ and gains a speed v₀.If it were accelerated instead through a potential difference of 2V₀,what speed would it gain?

A)8v₀
B)4v₀
C)2v₀
D)v₀

Question 13

Three equal-magnitude point charges of varying signs are placed at the corners of a square of side d as shown in the figure.Which one of the arrows shown represents the direction of the net field at the center of the square?

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

Question 14

A conductor is placed in a steady external electric field.Which of the following statements are correct for this situation? (There could be more than one correct choice.)

A)The electric field is zero inside the conductor.
B)All the free electrons go to the surface of the conductor.
C)The surface of the conductor is neutral.
D)The electric field just outside the surface of the conductor is perpendicular to the surface.
E)None of the above statements are correct.

Question 15

The figure shows two unequal charges,+q and -Q.Charge -Q has greater magnitude than charge +q.Point X is midway between the charges.In what section of the line will there be a point where the resultant field is zero?

A)VW
B)WX
C)XY
D)YZ

Question 16

Four tiny charged particles (two having a charge +Q and two having a charge -Q)are distributed on the x- and y-axes as shown in the figure.Each charge is equidistant from the origin.In which direction is the net field at the point P on the y-axis?

A)directly up (in the +y direction)
B)directly left (-x direction)
C)upwards and towards the left
D)upwards and towards the right
E)The net field is zero, so there is no direction.

Question 17

Three equal negative point charges -q are placed at three of the corners of a square of side d as shown in the figure.Which one of the arrows shown represents the direction of the net field at the vacant corner of the square?

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

Question 18

Three equal positive point charges +q are placed at the corners of a square of side d as shown in the figure.Which one of the arrows shown represents the direction of the net field at the center of the square?

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

Question 19

Three equal-magnitude point charges of varying signs are placed at three of the corners of a square of side d as shown in the figure.Which one of the arrows shown represents the direction of the net field at the vacant corner of the square?

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

Question 20

The electron-volt is a unit of

A)charge.
B)electric potential.
C) field.
D)electric force.
E)energy.

Question 21

A parallel-plate capacitor is connected to a battery and becomes fully charged.The capacitor is then disconnected,and the separation between the plates is increased in such a way that no charge leaks off.As the plates are being separated,the energy stored in this capacitor

A)increases.
B)decreases.
C)does not change.
D)become zero.

Question 22

A battery charges a parallel-plate capacitor fully and then is removed.The plates are then slowly pulled apart.What happens to the potential difference between the plates as they are being separated?

A)It increases.
B)It decreases.
C)It remains constant.
D)It cannot be determined from the information given.

Question 23

When a certain capacitor carries charges of ±10 µC on its plates,the potential difference cross the plates is 25 V.Which of the following statements about this capacitor are true? (There could be more than one correct choice.)

A)If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will also double.
B)If we double the charges on the plates to ±20 µC, the potential difference across the plates will also double.
C)If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will not change.
D)If we double the charges on the plates to ±20 µC, the potential difference across the plates will decrease by a factor of two.

Question 24

The plates of a parallel-plate capacitor are maintained with constant potential by a battery as they are pulled apart.During this process,the amount of charge on the plates

A)must increase.
B)must decrease.
C)must remain constant.
D)could either increase or decrease. There is no way to tell from the information given.

Question 25

Doubling the capacitance of a capacitor that is holding a constant charge causes the energy stored in that capacitor to

A)quadruple.
B)double.
C)decrease to one-half.
D)decrease to one-fourth.

Question 26

An ideal parallel-plate capacitor has a capacitance of C.If the area of the plates is doubled and the distance between the plates is halved,what is the new capacitance?

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

Question 27

The potential (relative to infinity)at the midpoint of a square is 3.0 V when a point charge of +Q is located at one of the corners of the square.What is the potential (relative to infinity)at the center when each of the other corners is also contains a point charge of +Q?

A)0 V
B)3.0 V
C)9.0 V
D)12 V

Question 28

The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity.What is the potential (relative to infinity)at a distance of 2 m from the same charge?

A)200 V
B)50 V
C)400 V
D)100 V
E)600 V

Question 29

Two ideal parallel-plate capacitors are identical in every respect except that one has twice the plate area of the other.If the smaller capacitor has capacitance C,the larger one has capacitance

A)C/2.
B)C.
C)2C.
D)4C.

Question 30

A capacitor consists of two large parallel plates of area A separated by a very small distance d.This capacitor is connected to a battery and charged until its plates carry charges +Q and -Q,and then disconnected from the battery.If the separation between the plates is now doubled,the potential difference between the plates will

A)double.
B)quadruple.
C)be cut in half.
D)be cut in fourth.
E)not change.

Question 31

If the field between the plates of a given air-filled capacitor is weakened by removing charge from the plates,the capacitance of that capacitor

A)increases.
B)decreases.
C)does not change.
D)It cannot be determined from the information given.

Question 32

Which statements must be true about the surface of a charged conductor in which no charge is moving? (There could be more than one correct choice.)

A)The field is zero at the surface.
B)The electric potential of the surface is zero.
C)The field is constant at the surface.
D)The electric potential is constant over the surface.
E)The field is perpendicular to the surface.

Question 33

If the result of your calculations for a quantity has SI units of C² ∙ s²/(kg ∙ m²),that quantity could be

A)an electric potential difference.
B)a dielectric constant.
C)an field.
D)a capacitance.
E)an electric potential energy.

Question 34

An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d.This capacitor is connected across a battery that maintains a constant potential difference between the plates.If the separation between the plates is now doubled,the magnitude of the charge on the plates will

A)double.
B)quadruple.
C)be cut in half.
D)be cut in fourth.
E)not change.

Question 35

The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pulled apart.What happens to the magnitude of the field between the plates during this process?

A)It increases.
B)It decreases.
C)It remains constant.
D)It cannot be determined from the information given.

Question 36

A region of space contains a uniform electric field,directed toward the right,as shown in the figure.Which statement about this situation is correct?

A)The potential at all three locations is the same.
B)The potentials at points A and B are equal, and the potential at point C is higher than the potential at point A.
C)The potential at points A and B are equal, and the potential at point C is lower than the potential at point A.
D)The potential at point A is the highest, the potential at point B is the second highest, and the potential at point C is the lowest.

Question 37

Doubling the potential across a given capacitor causes the energy stored in that capacitor to

A)quadruple.
B)double.
C)reduce to one-half.
D)reduce to one-fourth.

Question 38

Which of the following will increase the capacitance of a parallel-plate capacitor? (There could be more than one correct choice.)

A)a decrease in the plate area and an increase in the plate separation
B)a decrease in the potential difference between the plates
C)an increase in the potential difference between the plates
D)an increase in the plate area and a decrease in the plate separation
E)an increase in the charge on the plates

Question 39

An ideal parallel-plate capacitor having circular plates of diameter D that are a distance d apart stores energy U when it is connected across a fixed potential difference.If you want to triple the amount of energy stored in this capacitor by changing only the size of its plates,the diameter should be changed to

A)9D.
B)3D.
C)D
D)
E)

Question 40

Four charged particles (two having a charge +Q and two having a charge -Q)are arranged in the xy-plane,as shown in the figure.These particles are all equidistant from the origin.The electric potential (relative to infinity)at point P on the z-axis due to these particles,is

A)zero.
B)positive.
C)negative.
D)impossible to determine based on the information given.

Question 41

A pair of charged conducting plates produces a uniform field of 12,000 N/C,directed to the right,between the plates.The separation of the plates is 40 mm.An electron is projected from plate A,directly toward plate B,with an initial speed of v₀ = 2.0 × 10⁷ m/s.What is the speed of the electron as it strikes plate B? (e = 1.6 × 10^-19 C,m_electron = 9.11 × 10^-31 kg)

A)1.2 × 10⁷ m/s
B)1.5 × 10⁷ m/s
C)1.8 × 10⁷ m/s
D)2.1 × 10⁷ m/s
E)2.4 × 10⁷ m/s

Question 42

A particle with a charge of +4.0 μC has a mass of 5.0 g.What magnitude field directed upward will exactly balance the force that Earth exerts on the particle?

A)4.1 × 10⁴ N/C
B)8.2 × 10⁴ N/C
C)4.4 × 10⁴ N/C
D)1.2 × 10⁴ N/C
E)5.1 × 10⁴ N/C

Question 43

A small styrofoam ball of mass 0.120 g is placed at rest in an field of 6000 N/C pointing downward.What excess charge must be placed on the ball for it to remain suspended in the field?

A)-16.0 nC
B)-18.0 nC
C)-57.2 nC
D)-125 nC
E)-196 nC

Question 44

When a dielectric material is introduced between the plates of a parallel-plate capacitor and completely fills the space,the capacitance increases by a factor of 4.What is the dielectric constant of the material that was introduced?

A)0.4
B)1/4
C)2
D)4
E)None of the other choices is correct.

Question 45

A small 0.050-kg insulating sphere carries a charge of -60 μC and is hanging by a vertical silk thread from a fixed point in the ceiling.An external uniform vertical electric field is now applied.If the applied field has a magnitude of 3000 N/C and is directed downward,what is the tension force that the silk thread exerts on the sphere? (k = 1/4πε₀ = 9.0 × 10⁹ N ∙ m²/C²)

A)0.19 N
B)0.31 N
C)0.41 N
D)0.52 N
E)0.71 N

Question 46

What is the field 2.8 cm from a tiny object that carries an excess charge of -16 nC? (k = 1/4πε₀ = 9.0 × 10⁹ N ∙ m²/C²)

A)180,000 N/C
B)5100 N/C
C)1.8 × 10¹⁴ N/C
D)-180,000 N/C
E)-5100 N/C

Question 47

An electron is projected with an initial velocity v₀ = 8.4 × m/s along the y-axis,which is the centerline between a pair of charged plates,as shown in the figure.The plates are 1.0 m long and are separated by 0.10 m.A uniform field of known magnitude in the +x-direction is present between the plates.If the magnitude of the acceleration of the electron is measured to be what is the magnitude of the field between the plates? (e = 1.6 × 10^-19 C,m_electron = 9.11 × 10^-31 kg)

A)51,000 N/C
B)45,000 N/C
C)40,000 N/C
D)35,000 N/C
E)29,000 N/C

Question 48

If the electric field exerts a 27 mN force on a point charge of -30 µC at a certain location in the laboratory,what are the magnitude and direction of the field at that location?

Question 49

An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d.This capacitor is connected to a battery and charged until its plates carry charges +Q and -Q,and the battery is then disconnected.If the separation between the plates is now doubled,the electrical energy stored in the capacitor will

A)double.
B)quadruple.
C)be cut in half.
D)be cut in fourth.
E)not change.

Question 50

A small glass bead has been charged to 1.9 nC.What is the field 2.0 cm from the center of the bead? (k = 1/4πε₀ = 8.99 × 10⁹ N ∙ m²/C²)

A)4.3 × 10⁴ N/C
B)8.5 × 10² N/C
C)8.1 × 10^-5 N/C
D)8.5 × 10^-7 N/C

Question 51

Which of the following changes will increase the capacitance of a parallel-plate capacitor? (There could be more than one correct choice.)

A)increase the charge on the plates
B)decrease the potential between the plates
C)increase the potential between the plates
D)introduce a dielectric material between the plates
E)decrease the separation between the plates

Question 52

At a distance d from a point charge Q,the energy density in its electric field is u.If we now go to a distance d/2 from the charge,what is the energy density at the new location?

A)16u
B)8u
C)4u
D)2u
E)u

Question 53

An electron is placed in a uniform electric field of E = 4.5 × 104 N/C that points to the right.(e = 1.6 × 10^-19 C,m_electron = 9.11 × 10-31 kg)
(a)What are the magnitude and direction of the force exerted on the electron by the electric field?
(b)If the electron is released from rest,what is its speed after 3.0 ps?

Question 54

A small object with a 5.0-μC charge is accelerating horizontally on a friction-free surface at 0.0050 m/s2 due only to an electric field.If the object has a mass of 2.0 g,what is the magnitude of the field?

A)2.0 N/C
B)4.0 N/C
C)0.0020 N/C
D)0.0040 N/C
E)1.0 N/C

Question 55

At a distance d from a point charge Q,the energy density in its electric field is u.If we double the charge,what is the energy density at the same point?

A)16u
B)8u
C)4u
D)2u
E)u

Question 56

What should the magnitude of a vertical field be so that the force that the electric field exerts on a plastic sphere of mass that has been charged to -3.0 nC balances the force that Earth exerts on it? (k = 1/4πε₀ = 9.0 × 10⁹ N ∙ m²/C²)

A)6.9 × 10⁶ N/C
B)7.8 × 10⁵ N/C
C)1.5 × 10⁶ N/C
D)2.1 × 10⁶ N/C

Question 57

A parallel-plate capacitor consists of a set of two parallel plates of area A separated by a distance d.This capacitor is connected to a battery that maintains a constant potential difference across the plates.A slab of a dielectric material is inserted in the region between the plates and completely fills it.What changes would you observe as the dielectric is inserted? (There could be more than one correct choice.)

A)Only the charge on the plates of the capacitor would change.
B)Only the capacitance would change.
C)Both the charge on the plates of the capacitor and its capacitance would change.
D)The potential difference across the plates would increase.
E)Nothing would change.

Question 58

A proton is placed in an electric field E = 800 N/C.What are the magnitude and direction of the acceleration of the proton due to this field? (e = 1.60 × 10^-19 C,m_proton = 1.67 × 10^-27 kg)

A)7.66 × m/ opposite to the direction of the field
B)7.66 × m/ opposite to the direction of the field
C)7.66 × m/ in the direction of the field
D)76.6 × m/ opposite to the direction of the field
E)76.6 × m/ in the direction of the field

Question 59

An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d.This capacitor is connected to a battery that maintains a constant potential difference across the plates.If the separation between the plates is now doubled,the amount of electrical energy stored on the capacitor will

A)double.
B)quadruple.
C)be cut in half.
D)be cut in fourth.
E)not change.

Question 60

A dielectric material such as paper is inserted between the plates of a capacitor as the capacitor holds a fixed charge on its plates.What happens to the electric field between the plates as the dielectric is inserted?

A)There is no change in the field.
B)The field becomes stronger.
C)The field becomes weaker.
D)The field reduces to zero.

Question 61

A proton that is initially at rest is accelerated through an electric potential difference of magnitude 500 V.How much kinetic energy does it gain? (e = 1.60 × 10^-19

A)500 J
B)8.0 × 10^-17 J
C)
C)1.6 × 10^-19 J
D)800 J

Question 62

After a proton with an initial speed of 1.50 × 10⁵ m/s has increased its speed by accelerating through a potential difference of 0.100 kV,what is its final speed? (e = 1.60 × 10^-19 C ,m_proton = 1.67 × 10^-27 kg)

A)4.56 × 10⁵ m/s
B)2.04 × 10⁵ m/s
C)3.55 × 10⁵ m/s
D)8.80 × 10⁵ m/s
E)1.55 × 10⁶ m/s

Question 63

Two tiny particles having charges +20.0 μC and -8.00 μC are separated by a distance of 20.0 cm.What are the magnitude and direction of the field midway between these two charges? (k = 1/4πε₀ = 9.0 × 10⁹ N ∙ m²/C²)

A)25.2 × N/C directed towards the negative charge
B)25.2 × N/C directed towards the positive charge
C)25.2 × N/C directed towards the negative charge
D)25.2 × N/C directed towards the positive charge
E)25.2 × N/C directed towards the negative charge

Question 64

How much work is needed to carry an electron from the positive terminal to the negative terminal of a 9.0-V battery.(e = 1.60 × 10^-19 C ,m_electron = 9.11 × 10^-31 kg)

A)1.6 × 10^-19 J
B)17 × 10^-19 J
C)9.0 J
D)14.4 × 10^-19 J
E)14.4 × 10^-19 J/C

Question 65

A +5.00-μC point charge is placed at the 0.0 cm mark of a meter stick and a -4.00-μC point charge is placed at the 50.0 cm mark.At what point on a line through the ends of the meter stick is the field equal to zero?

A)1.4 m from the 0 cm mark
B)2.5 m from the 0 cm mark
C)2.9 m from the 0 cm mark
D)3.3 m from the 0 cm mark
E)4.7 m from the 0 cm mark

Question 66

Two parallel square metal plates,8.4 cm on each side,are 2.5 mm apart and carry equal but opposite charge uniformly distributed over their facing surfaces.How much excess charge is there on each plate if the field between the plates has a magnitude of 2.0 × 10⁶ N/C? (k = 1/4πε₀ = 8.99 × 10⁹ N ∙ m²/C²)

Question 67

An electric dipole consists of charges of ±6.00 µC that are 10.0 cm apart,as shown in the figure.Find the magnitude and direction of the field this dipole produces at point P,which is 7.00 cm from each charge.(k = 1/4πε₀ = 8.99 × 10⁹ N ∙ m²/C²)

Question 68

A tiny particle with charge + 5.0 μC is initially moving at 55 m/s.It is then accelerated through a potential difference of 500 V.How much kinetic energy does this particle gain during the period of acceleration?

A)1.0 × 10⁴ J
B)2.5 × 10^-3 J
C)100 J
D)2500 J

Question 69

A thin spherical copper shell of radius 9.5 cm carries an excess charge of -4.2 nC.How many excess electrons are on (a)the outer surface of the shell,and (b)the inner surface? (e = 1.60 × 10^-19C)

Question 70

A +5.0-μC point charge is placed at the 0 cm mark of a meter stick and a -4.0-μC charge is placed at the 50 cm mark.What is the net field at the 30 cm mark? (k = 1/4πε₀ = 8.99 × 10⁹ N ∙ m²/C²)

A)4.0 × 10⁵ N/C
B)5.0 × 10⁵ N/C
C)9.0 × 10⁵ N/C
D)1.4 × 10⁶ N/C

Question 71

Two large closely-spaced parallel metal plates are uniformly and oppositely charged and the magnitude of the field between them is 7.6 × 10⁶ N/C.
(a)What is the charge per unit area on each plate?
(b)If the plates are now moved two times farther apart,what is the magnitude of the field between the plates?

Question 72

A proton that is initially at rest is accelerated through an electric potential difference of magnitude 500 V.What speed does the proton gain? (e = 1.60 × 10^-19 C ,m_proton = 1.67 × 10^-27 kg)

A)2.2 × 10⁵ m/s
B)3.1 × 10⁵ m/s
C)9.6 × 10⁵ m/s
D)1.1 × 10⁵ m/s

Question 73

How much kinetic energy does a proton gain if it is accelerated,with no friction,through a potential difference of 1.00 V? The proton is 1836 times heavier than an electron,and e = 1.60 × 10^-19 C.

A)1836 eV
B)1.00 eV
C)1.60 × 10^-19 eV
D)1.00 J
E)1836 J

Question 74

If an electron is accelerated from rest through a potential difference of 1500 V,what speed does it reach? (e = 1.60 × 10^-19 C ,m_electron = 9.11 × 10^-31 kg)

A)2.3 × 10⁷ m/s
B)1.9 × 10⁷ m/s
C)1.5 × 10⁷ m/s
D)1.1 × 10⁷ m/s

Question 75

A tiny 0.0250-µg oil drop containing 15 excess electrons is suspended between two horizontally closely-spaced metal plates that carry equal but opposite charges on their facing surfaces.The plates are both circular with a radius of 6.50 cm.(k = 1/4πε₀ = 9.0 × 10⁹ N ∙ m²/C²,e = 1.6 × 10^-19
C)
(a)How much excess charge must be on each plate to hold the oil drop steady?
(b)Which plate must be positive, the upper one or the lower one?

Question 76

Two parallel square metal plates that are 1.5 cm apart and 22 cm on each side carry equal but opposite charges uniformly spread out over their facing surfaces.How many excess electrons are on the negative surface if the field between the plates has a magnitude of 18,000 N/C? (k = 1/4πε₀ = 9.0 × 10⁹ N ∙ m²/C²,e = 1.6 × 10^-19C)

Question 77

If it takes 50 J of energy to move 10 C of charge from point A to point B,what is the magnitude of the potential difference between points A and B?

A)500 V
B)50 V
C)5.0 V
D)0.50 V

Question 78

A proton with a speed of 2.0 x m/s accelerates through a potential difference and thereby increases its speed to 4.0 x m/s.Through what magnitude potential difference did the proton accelerate? (e = 1.60 × 10^-19 C ,m_proton = 1.67 × 10^-27 kg)

A)630 V
B)210 V
C)840 V
D)1000 V
E)100 V

Question 79

The field at a point 2.8 cm from a small object points toward the object and is equal to 180,000 N/C.What is the object's charge q? (k = 1/4πε₀ = 8.99 × 10⁹ N ∙ m²/C²)

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

Question 80

A 4.0-g bead carries a charge of 20 μC.The bead is accelerated from rest through a potential difference V,and afterward the bead is moving at 2.0 m/s.What is the magnitude of the potential difference V?

A)800 kV
B)400 kV
C)800 V
D)400 V
E)200 V