Phys 202 Chapter 19 Concepts

At which of the three labeled points is the electric field strongest? A. Point A B. Point B C. Point C D. We cannot determine the answer.

C. Point C

The figure below shows four parallel plate capacitors: A, B, C, and D. Each capacitor carries the same charge q and has the same plate area A. As suggested by the figure, the plates of capacitors A and C are separated by a distance d while those of B and D are separated by a distance 2d. Capacitors A and B are maintained in vacuum while capacitors C and D contain dielectrics with constant κ = 5. Which capacitor has the largest potential difference between its plates? a) A b) B c) C d) D e) A and D are the same and larger than B or C.

b) B

The location marked P in the drawing lies midway between the point charges +q and -q. The blue lines labeled A, B, and C are edge-on views of three planes. Which of the planes is an equipotential surface? a) A and C b) A, B, and C c) Only B d) None of the planes is an equipotential surface

c) Only B

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. What is the magnitude of the electric field at point A? a) 30 V/m b) 25 V/m c) 10 V/m d) 75 V/m e) 100 V/m

e) 100 V/m

P and Q are points within a uniform electric field that are separated by a distance of 0.2 m as shown. The potential difference between P and Q is 75 V. Determine the magnitude of this electric field. a) 750 V/m b) 15 V/m c) 75 V/m d) 1100 V/m e) 375 V/m

e) 375 V/m

The drawing shows edge-on views of three parallel plate capacitors with the same separation between the plates. The potential of each plate is indicated above it. Rank the capacitors as to the magnitude of the electric field inside them, largest to smallest. a) B, C, A b) A, B, C c) C, A, B d) C, B, A e) A, C, B

d) C, B, A

The electric potential V is constant everywhere within a certain region of space. Which statement below is true? a) The electric field varies from place to place within the region. b) A charged particle placed within the region will experience an electric force. c) The electric field is also constant (but not zero) within the region. d) The electric field is zero everywhere within the region.

d) The electric field is zero everywhere within the region.

The drawing shows three possibilities for the potentials at two points, A and B. In each case, the same positive charge is moved from A to B. In which case, if any, is the most work done on the positive charge by the electric force? a) Case 1 b) Case 2 c) Case 3 d) The work is the same in all three cases

d) The work is the same in all three cases

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. What is the direction of the electric field at B? a) up and out of the page b) toward A c) toward C d) toward D e) into the page

d) toward D

The drawing shows a cross-sectional view of two spherical equipotential surfaces and two electric field lines that are perpendicular to these surfaces. When an electron moves from point A to point B (against the electric field), the electric force does +3.2 x 10-19 J of work. What are the electric potential differences (a) VB - VA, (b) VC - VB, and (c) VC - VA? A) (a) +2.0 V, (b) 0 V, (c) +2.0 V B) (a) -2.0 V, (b) 0 V, (c) -2.0 V C) (a) +2.0 V, (b) -2.0 V, (c) 0 V D) (a) 0 V, (b) 0 V, (c) 0 V

A) (a) +2.0 V, (b) 0 V, (c) +2.0 V

An electric potential energy exists when two protons are separated by a certain distance. Does the electric potential energy increase, decrease, or remain the same (a) when both protons are replaced by electrons, and (b) when only one of the protons is replaced by an electron? A) (a) remain the same, (b) decrease B) (a) remain the same, (b) increase C) (a) decrease, (b) increase D) (a) increase, (b) decrease

A) (a) remain the same, (b) decrease

What additional information is needed to calculate the work done while pushing the point charge at constant speed from A to B along path 1? I. The charge of the point charge II. The charge of the asymmetric blob III. The electric field along that path A. I only B. I and II C. I and III D. I, II, and III

A. I only

The net charge of the asymmetric blob is: A. Positive B. Negative C. Zero D. We cannot determine the answer.

A. Positive

The point charge has charge 0.01 coulombs. How much work is needed to push it from A to C along the equipotential line containing those two points? A. -0.2 joules B. 0 joules C. 0.2 joules D. We need more information.

B. 0 joules

Which student, if either, is correct about the work required to push the point charge along path 1 vs. path 2? A. Student 1 B. Student 2 C. Neither student 1 nor student 2 D. We cannot determine who is correct without more information.

C. Neither student 1 nor student 2

An ion, starting from rest, accelerates from point A to point B due to a potential difference between the two points. Does the electric potential energy of the ion at point B depend on (a) the magnitude of its charge and (b) its mass? Does the speed of the ion at B depend on (c) the magnitude of its charge and (d) its mass? A) (a) Yes. (b) No. (c) Yes. (d) No. B) (a) Yes. (b) Yes. (c) Yes. (d) Yes. C) (a) No. (b) No. (c) No. (d) No. D) (a) Yes. (b) No. (c) Yes. (d) Yes.

D) (a) Yes. (b) No. (c) Yes. (d) Yes.

Imagine that you are moving a positive test charge along the line between two identical point charges. With regard to the electric potential, is the midpoint on the line analogous to the top of a mountain or the bottom of a valley when the two point charges are (a) positive and (b) negative? A) (a) top of a mountain (b) bottom of a valley B) (a) bottom of a valley (b) bottom of a valley C) (a) top of a mountain (b) top of a mountain D) (a) bottom of a valley (b) top of a mountain

D) (a) bottom of a valley (b) top of a mountain

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. How much work is required to move a -1.0 μC charge from A to E? a) +7.0 × 10-5 J b) zero joules c) -7.0 × 10-5 J d) -4.0 × 10-5 J e) +3.0 × 10-5 J

a) +7.0 × 10-5 J

The drawing shows four arrangements of two point charges. In each arrangement consider the total electric potential that the charges produce at location P. Rank the arrangements (largest to smallest) according to the total potential. a) B, C, A and D (a tie) b) D, C, A, B c) C, D, A, B d) A and C (a tie), B, D

a) B, C, A and D (a tie)

Two different charges, q1 and q2, are placed at two different locations, one charge at each location. The locations have the same electric potential V. Do the charges have the same electric potential energy? a) No, because the electric potential energy EPE at a given location depends on the charge placed at that location as well as the electric potential V. b) Yes. If the electric potentials at the two locations are the same, the electric potential energies are also the same, regardless of the type (+ or -) and magnitude of the charges placed at these locations. c) No, because the electric potential V at a given location depends on the charge placed at that location, whereas the electric potential energy EPE does not. d) Yes, because electric potential and electric potential energy are just different names for the same concept.

a) No, because the electric potential energy EPE at a given location depends on the charge placed at that location as well as the electric potential V.

What happens to a capacitor when an insulator is inserted between the two conductors of the capacitor? a) The capacitance of the capacitor increases. b) There is no change to the capacitor. The insulator just keeps the two conductors separated. c) The insulator reduces the electric field between the two conductors. d) Electrons from the negative plate travel to the positive plate. e) The electric field inside the capacitor increases.

a) The capacitance of the capacitor increases.

Consider a spot that is located midway between two identical point charges. Which one of the following statements concerning the electric field and the electric potential at this spot is true? a) The electric field is zero, but the electric potential is not zero. b) Neither the electric field nor the electric potential is zero. c) The electric field is not zero, but the electric potential is zero. d) Both the electric field and the electric potential are zero.

a) The electric field is zero, but the electric potential is not zero.

A parallel plate capacitor is charged up by a battery. The battery is then disconnected, but the charge remains on the plates. The plates are then pulled apart. Does the energy stored by the capacitor increase, decrease or remain the same as the distance between the plates increases? a) increase b) decrease c) remain the same

a) increase

An empty parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. With the battery connected, a dielectric is then inserted between the plates. Does the energy stored by the capacitor increase, decrease or remain the same when the dielectric is inserted? a) increase b) remain the same c) decrease

a) increase

A positive test charge is placed in an electric field. In what direction should the charge be moved relative to the field, so that the charge experiences a constant electric potential? The charge should be moved a) perpendicular to the electric field. b) in the same direction as the electric field. c) opposite to the direction of the electric field.

a) perpendicular to the electric field.

P and Q are points within a uniform electric field that are separated by a distance of 0.2 m as shown. The potential difference between P and Q is 75 V. How much work is required to move a +150 μC point charge from P to Q? a) 75 J b) 0.011 J c) 140 J d) 0.023 J e) 2800 J

b) 0.011 J

The drawing shows a plot of the electric potential V versus the displacement s. The plot consists of four segments. Rank the magnitude of the electric fields for the four segments, largest to smallest. a) A and C (a tie), B and D (a tie) b) D, B, A and C (a tie) c) D, C, B, A d) B, D, C, A e) A, B, D, C

b) D, B, A and C (a tie)

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. At which of the labeled points will an electron have the greatest potential energy? a) D b) H c) A d) G e) I

b) H

In a region of space where the electric field is constant everywhere, as it is inside a parallel plate capacitor, is the potential constant everywhere? a) Yes. b) No, the potential is greatest at the positive plate. c) No, the potential is greatest at the negative plate.

b) No, the potential is greatest at the positive plate.

A proton is released from rest at point A in a constant electric field and accelerates to point B (see part a of the drawing). An electron is released from rest at point B and accelerates to point A (see part b of the drawing). How does the change in the proton's electric potential energy compare with the change in the electron's electric potential energy? a) The proton experiences a smaller change in electric potential energy, since it has a smaller charge magnitude. b) The change in the proton's electric potential energy is the same as the change in the electron's electric potential energy. c) One cannot compare the change in potential energies because the proton and electron move in opposite directions. d) The proton experiences a greater change in electric potential energy, since it has a greater charge magnitude. e) The proton experiences a smaller change in electric potential energy, since it has a smaller speed at B than the electron has at A. This is due to the larger mass of the proton.

b) The change in the proton's electric potential energy is the same as the change in the electron's electric potential energy.

The drawing shows two different charge configurations, but in each case a charge q is located at the origin. A charge q0 is placed a distance r from the origin (top drawing), and a charge 2q0 is placed a distance 2r from the origin (bottom drawing). All charges are positive. Which statement is true regarding the electric potential energy EPE (not the electric potential V) of the charges in the top drawing relative to those in the bottom drawing? a) The charges in the bottom drawing have a greater electric potential energy because they have a greater total charge. b) The charges in the top drawing have the same electric potential energy as those in the bottom drawing. c) The charges in the top drawing have a greater electric potential energy because they are closer together. d) The charges in the top drawing have a smaller electric potential energy because they are closer together.

b) The charges in the top drawing have the same electric potential energy as those in the bottom drawing.

Points A, B, and C lie along a line from left to right, respectively. Point B is at a lower electric potential than point A. Point C is at a lower electric potential than point B. Which one of the following statements best describes the subsequent motion, if any, of a positively-charged particle released from rest at point B? a) The particle will move at constant velocity in the direction of point A. b) The particle will accelerate in the direction of point C. c) The particle will move at constant velocity in the direction of point C. d) The particle will remain at rest. e) The particle will accelerate in the direction of point A.

b) The particle will accelerate in the direction of point C.

A proton and an electron are released from rest at the midpoint between the plates of a charged parallel plate capacitor. Except for these particles, nothing else is between the plates. Ignore the attraction between the proton and the electron, and decide which particle strikes a capacitor plate first. a) the proton b) the electron c) they strike the plates at the same time

b) the electron

A proton is fixed in place. An electron is released from rest and allowed to collide with the proton. Then the roles of the proton and electron are reversed, and the same experiment is repeated. Which, if either, is traveling faster when the collision occurs, the proton or the electron? a) the proton b) the electron c) they are traveling at the same speed

b) the electron

A charge q = -6.0 µC is moved 0.25 m horizontally to point P in a region where an electric field is 250 V/m directed vertically, as shown. What is the change in the electric potential energy of the charge? a) +1.5 × 10-4 J b) zero joules c) +2.4 × 10-5 J d) -2.4 × 10-5 J e) -1.5 × 10-4 J

b) zero joules

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. What is the potential difference between points B and E? a) 60 V b) 10 V c) 50 V d) 40 V e) 30 V

c) 50 V

A positively-charged particle is held at point A between two parallel metal plates. The plate on the left has a net positive charge +q and the plate on the right has a net negative charge -q. The particle is then moved to point B which is far from other charges. How does the electric potential energy at point A compare with that at point B? a) EPEA > EPEB or EPEA < EPEB depending on the actual distances from the points to the plates. b) EPEA = EPEB c) EPEA > EPEB d) EPEA < EPEB

c) EPEA > EPEB

Which one of the following statements concerning equipotential surfaces is false? a) There is a quantitative relationship between the electric field and the associated equipotential surfaces that surround one or more charges. b) The electric field created by one or more charges points in the direction of decreasing potential. c) No work is done by the net electric force as a charge moves from one equipotential surface to another. d) The electric field created by one or more charges is everywhere perpendicular to the associated equipotential surfaces. e) All points on an equipotential surface have the same electric potential.

c) No work is done by the net electric force as a charge moves from one equipotential surface to another.

A parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. If the plates are pulled away from each other, increasing their separation, what happens to the amount of charge on the plates? a) The amount of the charge increases, because the capacitance decreases. b) The amount of the charge increases, because the capacitance increases. c) The amount of the charge decreases, because the capacitance decreases. d) Nothing happens; the amount of charge stays the same. e) The amount of the charge decreases, because the capacitance increases.

c) The amount of the charge decreases, because the capacitance decreases.

The length and width of each plate of a parallel plate capacitor are doubled, and the spacing between the plates is also doubled. By what factor does the capacitance change? a) The capacitance increases by a factor of 4. b) The capacitance increases by a factor of 8. c) The capacitance increases by a factor of 2. d) The capacitance decreases by a factor of 2. e) The capacitance decreases by a factor of 4.

c) The capacitance increases by a factor of 2.

When the distance between charged parallel plates of a capacitor is d, the potential difference is V. If the distance is decreased to d/2, how will the potential difference change, if at all? a) The new potential difference would be twice the previous value. b) The new potential difference would be the same as the previous value. c) The new potential difference would be one-half of the previous value. d) The new potential difference would be four times the previous value. e) The new potential difference would be one-fourth of the previous value.

c) The new potential difference would be one-half of the previous value.

Which one of the following changes will necessarily increase the capacitance of a capacitor? a) increasing the potential difference between the plates b) decreasing the charge on the plates c) placing a dielectric between the plates d) increasing the charge on the plates e) decreasing the potential difference between the plates

c) placing a dielectric between the plates

Complete the following statement: When a dielectric with constant κ is inserted between the plates of a charged isolated capacitor a) the capacitance is reduced by a factor κ. b) the charge on the plates is increased by a factor of κ. c) the electric field between the plates is reduced by a factor of κ. d) the potential difference between the plates is increased by a factor of κ. e) the charge on the plates is reduced by a factor of κ.

c) the electric field between the plates is reduced by a factor of κ.

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. How much work is required to move a -1.0 μC charge from B through D to C? a) +2.0 × 10-5 J b) +4.0 × 10-5 J c) zero joules d) -4.0 × 10-5 J e) -2.0 × 10-5 J

c) zero joules

The electric potential at a certain point in space is 12 V. What is the electric potential energy of a -3.0 μC charge placed at that point? a) +4 μJ b) +36 μJ c) -4 μJ d) -36 μJ e) zero µJ

d) -36 μJ

Which two, or more, of the following actions would increase the energy stored in a parallel plate capacitor when a constant potential difference is applied across the plates? a) 1, 3 b) 2, 4 c) 2, 3, 5 d) 1, 4, 5

d) 1, 4, 5

A completely ionized beryllium atom (net charge = +4e) is accelerated through a potential difference of 6.0 V. What is the increase in kinetic energy of the atom? a) 6.0 eV b) zero eV c) 4.0 eV d) 24 eV e) 0.67 eV

d) 24 eV

The drawing shows three arrangements of charged particles, all the same distance from the origin. Rank the arrangements, largest to smallest, according to the total electric potential V at the origin. a) B, C, A b) B, A, C c) A, B, C d) A and C (a tie), B e) A, B and C (a tie)

d) A and C (a tie), B

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. At which of the labeled points will the electric field have the greatest magnitude? a) H b) A c) D d) I e) G

d) I

Point charge A is located at point A and point charge B is at point B. Points A and B are separated by a distance r. To determine the electric potential at the mid-point along a line between points A and B, which of the following mathematical approaches is correct? a) The electric potential due to each charge is determined at a distance r/2 from each of the charges and an average is taken of the two values. b) The vector sum of the two electric potentials determines the total electric potential at a distance r/2 from each of the charges. c) The difference in the absolute value (the sign of the charges does not enter into the calculation) of the two electric potentials is determined at a distance r/2 from each of the charges. d) The algebraic sum of the two electric potentials is determined at a distance r/2 from each of the charges, making sure to include the signs of the charges.

d) The algebraic sum of the two electric potentials is determined at a distance r/2 from each of the charges, making sure to include the signs of the charges.

A point charge q is located at the origin. A charge q0 can be placed at a point P1, which is a distance r from the origin (top drawing). Or, a charge 2q0 can be placed at P2, which is a distance 2r from the origin (bottom drawing). All charges are positive. Which statement is true about the electric potentials due charge q at P1 and P2? a) The electric potential at P1 is less than that at P2, because q0 is smaller than 2q0. b) The electric potential at P1 is less than that at P2, because r is smaller than 2r. c) The electric potential at P1 is the same as that at P2. d) The electric potential at P1 is greater than that at P2, because r is smaller than 2r.

d) The electric potential at P1 is greater than that at P2, because r is smaller than 2r.

An isolated system consists of two conducting spheres A and B. Sphere A has five times the radius of sphere B. Initially, the spheres are given equal amounts of positive charge and are isolated from each other. The two spheres are then connected by a conducting wire.Note: The potential of a sphere of radius R that carries a charge Q is V = kQ/R, if the potential at infinity is zero. Which one of the following statements is true after the spheres are connected by the wire? a) The electric potential of A is 1/5 as large as that of B. b) The electric potential of A is five times larger than that of B. c) The electric potential of A is 25 times larger than that of B. d) The electric potential of A equals that of B. e) The electric potential of A is 1/25 as large as that of B.

d) The electric potential of A equals that of B.

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. A positive point charge is placed at F. Complete the following statement: When it is released, a) a force will cause it to move toward E. b) no force will be exerted on it. c) a force will cause it to move toward G. d) a force will cause it to move away from E. e) it would subsequently lose kinetic energy.

d) a force will cause it to move away from E.

A positive charge is moving from point A to point B in a uniform electric field, as shown in the drawing. The electric force does __________ work on the charge and, as a consequence, its electric potential energy _______. a) positive, increases b) negative, decreases c) positive, decreases d) negative, increases e) negative, does not change

d) negative, increases

A conducting sphere is connected via a wire to the ground. For a very short time, electrons move from the ground to the sphere. Then, no more electrons move to the sphere. Complete the following sentence: Before the wire was connected, the sphere's electric potential had a a) value that could have been either positive or negative. b) value equal to zero volts. c) negative value. d) positive value.

d) positive value.

Four point charges have the same magnitude (but they may have different signs) and are placed at the corners of a square, as the drawing shows. What must be the sign (+ or -) of each charge so that both the electric field and the electric potential are zero at the center of the square? Assume that the potential has a zero value at infinity. a) All of the charges are negative. b) All of the charges are positive. c) q1 and q2 are positive. q3 and q4 are negative. d) q1 and q3 are positive. q2 and q4 are negative.

d) q1 and q3 are positive. q2 and q4 are negative.

Four pairs of charged particles with identical separations are shown in the drawing. Rank the pairs according to their electric potential energy EPE, greatest (most positive) first. a) A and B (a tie), C, D b) C, B, D, A c) B, A, C and D (a tie) d) A, B, C, D e) A and C (a tie), B and D (a tie)

e) A and C (a tie), B and D (a tie)

The figure below shows four parallel plate capacitors: A, B, C, and D. Each capacitor carries the same charge q and has the same plate area A. As suggested by the figure, the plates of capacitors A and C are separated by a distance d while those of B and D are separated by a distance 2d. Capacitors A and B are maintained in vacuum while capacitors C and D contain dielectrics with constant κ = 5. Which capacitor is storing the greatest amount of electric potential energy? a) D b) Since all four carry the same charge, each will store the same amount of energy. c) C d) A e) B

e) B

The figure below shows four parallel plate capacitors: A, B, C, and D. Each capacitor carries the same charge q and has the same plate area A. As suggested by the figure, the plates of capacitors A and C are separated by a distance d while those of B and D are separated by a distance 2d. Capacitors A and B are maintained in vacuum while capacitors C and D contain dielectrics with constant κ = 5. Which list below places the capacitors in order of increasing capacitance? a) D, C, B, A b) A, B, D, C c) B, A, C, D d) A, B, C, D e) B, A, D, C

e) B, A, D, C

Which one of the following statements best describes the equipotential surfaces surrounding a point charge? a) The equipotential surfaces are concentric cylinders with the charge on the axis at the center. b) The equipotential surfaces are concentric cubes with the charge at the center. c) The equipotential surfaces are planes extending radially outward from the charge. d) The equipotential surfaces are curved planes surrounding the charge, but only one passes through the charge. e) The equipotential surfaces are concentric spheres with the charge at the center.

e) The equipotential surfaces are concentric spheres with the charge at the center.

Which one of the following statements concerning equipotential surfaces is true? a) The electric potential at points on each equipotential surface is equal to that of all other equipotential surfaces. b) Equipotential surfaces are a three dimensional representation of electric field lines. c) The net work done by electric forces that move a charge from one equipotential surface to another is equal to zero joules. d) The electric field lines are directed parallel to the equipotential surface. e) The net work done by electric forces that move a charge along an equipotential surface is equal to zero joules.

e) The net work done by electric forces that move a charge along an equipotential surface is equal to zero joules.

A +1.0 μC point charge is moved from point A to B in the uniform electric field as shown. Which one of the following statements is necessarily true concerning the potential energy of the point charge? a) The potential energy increases by 10.8 × 10-6 J. b) The potential energy decreases by 10.8 × 10-6 J. c) The potential energy decreases by 6.0 × 10-6 J. d) The potential energy increases by 6.0 × 10-6J. e) The potential energy decreases by 9.0 × 10-6 J.

e) The potential energy decreases by 9.0 × 10-6 J.

A battery charges capacitor A until the potential difference between the two conductors of the capacitor is V. A second, identical capacitor, labeled B, is charged by another battery until the potential difference of capacitor B is 2V. How does the stored energy of capacitor B compare to that of capacitor A? a) The stored energy of capacitor B is one-fourth that of capacitor A. b) The stored energy of capacitor B is one-half that of capacitor A. c) The stored energy of capacitor B is twice that of capacitor A. d) The stored energy in both capacitors is the same since the capacitance of both is the same. e) The stored energy of capacitor B is four times that of capacitor A.

e) The stored energy of capacitor B is four times that of capacitor A.

Consider the two charged particles situated as follows: One charge located on the y axis has a value -2q and is located at a distance r from the origin, point O. The other charge has a value -q and is located at a distance 2r from the origin along the x axis. Which one of the following statements concerning the electric potential at the origin is true? a) The total electric potential at the origin cannot be calculated since the charges are on different axes. b) The total electric potential at the origin is equal to -3kq/2r. c) The total electric potential at the origin is equal to zero volts. d) The total electric potential at the origin is equal to -2kq/r. e) The total electric potential at the origin is equal to -5kq/2r.

e) The total electric potential at the origin is equal to -5kq/2r.