Deck 20: Magnetism

Question 1

Choose the one alternative that best completes the statement or answers the question.
A charged particle that is moving in a static uniform magnetic field

A) may experience a magnetic force, but its speed will not change.
B) may experience a magnetic force which will cause its speed to change.
C) will always experience a magnetic force, regardless of its direction of motion.
D) may experience a magnetic force, but its direction of motion will not change.
E) None of the above statements are true.

Answer 1

A

Question 2

Choose the one alternative that best completes the statement or answers the question.

Answer 2

D

Question 3

Choose the one alternative that best completes the statement or answers the question.
An electron, moving west, enters a magnetic field. Because of this field the electron curves upward. We may conclude that the magnetic field must have a component

A) towards the south.
B) upward.
C) downward.
D) towards the north.
E) towards the west.

Answer 3

D

Question 4

Choose the one alternative that best completes the statement or answers the question.
A proton is to orbit Earth at the equator using Earth's magnetic field to supply part of the necessary centripetal force. In what direction should the proton move?

A) southward
B) eastward
C) westward
D) upward
E) northward

Question 5

Choose the one alternative that best completes the statement or answers the question.

Question 6

Choose the one alternative that best completes the statement or answers the question.
A proton, moving east, enters a magnetic field. Because of this magnetic field the proton curves downward. We may conclude that the magnetic field must have a component

A) towards the west.
B) downward.
C) towards the north.
D) towards the south.
E) upward.

Question 7

Choose the one alternative that best completes the statement or answers the question.

Question 8

Choose the one alternative that best completes the statement or answers the question.
An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, then the magnetic field must have a component

A) along the -y-axis
B) along the +y-axis
C) along the -x-axis
D) along the -z-axis
E) along the +z-axis

Question 9

Choose the one alternative that best completes the statement or answers the question.
If you were to cut a small permanent bar magnet in half,

A) each piece would in itself be a smaller bar magnet with both north and south poles.
B) one piece would be a magnetic north pole and the other piece would be a south pole.
C) neither piece would be magnetic.
D) None of these statements is true.

Question 10

Choose the one alternative that best completes the statement or answers the question.
An electron, moving south, enters a magnetic field. Because of this field, the electron curves upward. We may conclude that the magnetic field must have a component

A) upward.
B) towards the north.
C) towards the east.
D) towards the west.
E) downward.

Question 11

Choose the one alternative that best completes the statement or answers the question.

Question 12

Choose the one alternative that best completes the statement or answers the question.

Question 13

Choose the one alternative that best completes the statement or answers the question.

Question 14

Choose the one alternative that best completes the statement or answers the question.
A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward. We may conclude that the magnetic field must have a component

A) downward.
B) towards the west.
C) upward.
D) towards the east.
E) towards the north.

Question 15

Choose the one alternative that best completes the statement or answers the question.

Question 16

Choose the one alternative that best completes the statement or answers the question.
A straight bar magnet is initially 4 cm long, with the north pole on the right and the south pole on the left. If you cut the magnet in half, the right half will

A) contain only a south pole.
B) contain only a north pole.
C) contain a north pole on the right and a south pole on the left.
D) no longer contain any poles.

Question 17

Choose the one alternative that best completes the statement or answers the question.
A proton, moving west, enters a magnetic field. Because of this magnetic field the proton curves upward. We may conclude that the magnetic field must have a component

A) towards the west.
B) towards the north.
C) towards the south.
D) towards the east.
E) downward.

Question 18

Choose the one alternative that best completes the statement or answers the question.

Question 19

Choose the one alternative that best completes the statement or answers the question.

Question 20

Choose the one alternative that best completes the statement or answers the question.
Which one of the following statements is correct?

A) Earth's geographic north pole is the north pole of Earth's magnetic field.
B) Earth's geographic south pole is the south pole of Earth's magnetic field.
C) The north pole of a magnet points towards Earth's geographic south pole.
D) The north pole of a magnet points towards Earth's geographic north pole.
E) None of the above statements is correct.

Question 21

Choose the one alternative that best completes the statement or answers the question.
The magnetic force on a current-carrying wire in a magnetic field is the strongest when

A) the current is perpendicular to the magnetic field lines.
B) the current is in the direction of the magnetic field lines.
C) the current is at a 180° angle with respect to the magnetic field lines.
D) the current is at a 0° angle with respect to the magnetic field lines.
E) the current is in the direction opposite to the magnetic field lines.

Question 22

Choose the one alternative that best completes the statement or answers the question.

Question 23

Choose the one alternative that best completes the statement or answers the question.
After landing on an unexplored Klingon planet, Spock tests for the direction of the magnetic field by firing a beam of electrons in various directions and by recording the following observations:
Electrons moving upward feel a magnetic force in the northwest direction.
Electrons moving horizontally toward the north are pushed downward.
Electrons moving horizontally toward the southeast are pushed upward.
Mr) Spock therefore concludes that the magnetic field at this landing site is in which direction?

A) toward the southeast
B) toward the west
C) toward the east
D) toward the northeast
E) toward the southwest

Question 24

Choose the one alternative that best completes the statement or answers the question.

Question 25

Choose the one alternative that best completes the statement or answers the question.
A charged particle moves with a constant speed through a region where a uniform magnetic field is present. If the magnetic field points straight upward, the magnetic force acting on this particle
Will be strongest when the particle moves

Question 26

Choose the one alternative that best completes the statement or answers the question.
A negatively-charged particle moves across a constant uniform magnetic field that is perpendicular to the velocity of the particle. The magnetic force on this particle

A) causes the particle to speed up.
B) is in the same direction as the particle's velocity.
C) causes the particle to accelerate.
D) is opposite the direction of the particle's velocity.
E) causes the particle to slow down.

Question 27

Choose the one alternative that best completes the statement or answers the question.

Question 28

Choose the one alternative that best completes the statement or answers the question.
A proton, moving in a uniform magnetic field, moves in a circle perpendicular to the field lines and takes time T for each circle. If the proton's speed tripled, what would now be its time to go around
Each circle?

Question 29

Choose the one alternative that best completes the statement or answers the question.
A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field lines. Ignoring the particle's weight, the particle will

A) follow a circular path.
B) follow a spiral path.
C) move along a parabolic path.
D) move in a straight line.

Question 30

Choose the one alternative that best completes the statement or answers the question.

Question 31

Choose the one alternative that best completes the statement or answers the question.
A particle carrying a charge of +e travels in a circular path of radius R in a uniform magnetic field. If instead the particle carried a charge of +2e, the radius of the circular path would have been

Question 32

Choose the one alternative that best completes the statement or answers the question.
An electron has an initial velocity to the south but is observed to curve upward as the result of a magnetic field. This magnetic field must have a component

A) to the west.
B) downward.
C) to the north.
D) to the east.
E) upward.

Question 33

Choose the one alternative that best completes the statement or answers the question.

Question 34

Choose the one alternative that best completes the statement or answers the question.
At a particular instant, a proton moves toward the east in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it is

A) downward.
B) zero.
C) toward the south.
D) toward the north.
E) upward.

Question 35

Choose the one alternative that best completes the statement or answers the question.
The direction of the force on a current-carrying wire in a magnetic field is

A) perpendicular only to the magnetic field.
B) in same direction as the current.
C) in the direction opposite to the current.
D) perpendicular to both the current and the magnetic field.
E) perpendicular only to the current.

Question 36

Choose the one alternative that best completes the statement or answers the question.
A proton has an initial velocity to the south but is observed to curve upward as the result of a magnetic field. This magnetic field must have a component

A) downward.
B) to the east.
C) upward.
D) to the north.
E) to the west.

Question 37

Choose the one alternative that best completes the statement or answers the question.
A wire is carrying current vertically downward. What is the direction of the force on this wire due to Earth's magnetic field?

A) horizontally towards the west
B) vertically upward
C) horizontally towards the north
D) horizontally towards the east
E) horizontally towards the south

Question 38

Choose the one alternative that best completes the statement or answers the question.
A charged particle is observed traveling in a circular path of radius R in a uniform magnetic field. If the particle were traveling twice as fast, the radius of the circular path would be

Question 39

Choose the one alternative that best completes the statement or answers the question.

Question 40

Choose the one alternative that best completes the statement or answers the question.
At a particular instant, an electron moves toward the east in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it is

A) zero.
B) toward the south.
C) upward.
D) downward.
E) toward the north.

Question 41

Choose the one alternative that best completes the statement or answers the question.
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in opposite directions,

A) both wires are lifted slightly.
B) the wires pull toward each other.
C) one wire is lifted slightly while the other wire is forced downward against the table's surface.
D) the wires push away from each other.

Question 42

Choose the one alternative that best completes the statement or answers the question.
The maximum torque on a flat current-carrying loop occurs when the angle between the plane of the loop's area and the magnetic field vector is

Question 43

Choose the one alternative that best completes the statement or answers the question.
When two long parallel wires carry unequal currents, the magnitude of the magnetic force that one wire exerts on the other is F. If the current in both wires is now doubled, what is the magnitude of
The new magnetic force on each wire?

Question 44

Choose the one alternative that best completes the statement or answers the question.
Two long, parallel wires carry currents of different magnitudes. If the amount of current in one of the wires is doubled, what happens to the magnitude of the force that each wire exerts on the
Other?

Question 45

Choose the one alternative that best completes the statement or answers the question.
A flat circular wire loop lies in a horizontal plane on a table and carries current in a counterclockwise direction when viewed from above. At this point, the earth's magnetic field
Points to the north and dips below the horizontal. Which side of the coil tends to lift off of the table
Due to the magnetic torque on the loop?

A) the north side
B) the west side
C) the east side
D) the south side
E) The entire loop lifts straight up.

Question 46

Choose the one alternative that best completes the statement or answers the question.
A long, straight, horizontal wire carries current toward the east. An electron moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the
Electron?

A) toward the west.
B) toward the south
C) toward the north
D) downward
E) upward

Question 47

Choose the one alternative that best completes the statement or answers the question.

Question 48

Choose the one alternative that best completes the statement or answers the question.
A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire as you view it in such
A way that the current is coming directly toward you?

Question 49

Choose the one alternative that best completes the statement or answers the question.

Question 50

Choose the one alternative that best completes the statement or answers the question.

Question 51

Choose the one alternative that best completes the statement or answers the question.
Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at a point exactly between the two wires

A) is zero.
B) points away from you.
C) points toward you.
D) points downward.
E) points upward.

Question 52

Choose the one alternative that best completes the statement or answers the question.
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in the same direction,

A) both wires are lifted slightly.
B) the wires pull toward each other.
C) the wires push away from each other.
D) one wire is lifted slightly while the other wire is forced downward against the table's surface.

Question 53

Choose the one alternative that best completes the statement or answers the question.
Two long, parallel wires carry currents of different magnitudes. If the current in one of the wires is doubled and the current in the other wire is halved, what happens to the magnitude of the
Magnetic force that each wire exerts on the other?

A) It is reduced by a factor of two.
B) It is doubled.
C) It is quadrupled.
D) It is tripled.
E) It stays the same.

Question 54

Choose the one alternative that best completes the statement or answers the question.
A wire lying in the plane of this page carries a current directly toward the top of the page. What is the direction of the magnetic force this current produces on an electron that is moving
Perpendicular to the page and outward from it on the left side of the wire?

A) toward the bottom of the page
B) toward the top of the page
C) perpendicular to the page and towards you
D) perpendicular to the page and away from you
E) The force is zero.

Question 55

Choose the one alternative that best completes the statement or answers the question.
Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current directly toward you, and the wire on
Your left carries current directly away from you. From your point of view, the magnetic field at a
Point exactly midway between the two wires

A) points away from you.
B) points upward.
C) is zero.
D) points downward.
E) points toward you.

Question 56

Choose the one alternative that best completes the statement or answers the question.
Two long parallel wires are placed side-by-side on a horizontal table and carry current in the same direction. The current in one wire is 20 A, and the current in the other wire is 5 A. If the
Magnetic force on the 20-A wire has magnitude F, what is the magnitude of the magnetic force on
The 5-A wire? No external magnetic fields are present.

Question 57

Choose the one alternative that best completes the statement or answers the question.
An object is hung using a metal spring. If now a current is passed through the spring, what will happen to this system?

A) The spring will extend, lowering the weight.
B) The spring will begin to swing like a pendulum.
C) The spring will contract, raising the weight.
D) The weight will not move.
E) None of these are true.

Question 58

Choose the one alternative that best completes the statement or answers the question.
A long, straight, horizontal wire carries current toward the east. A proton moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the proton?

A) upward
B) toward the north
C) toward the east.
D) downward
E) toward the south

Question 59

Choose the one alternative that best completes the statement or answers the question.

Question 60

Choose the one alternative that best completes the statement or answers the question.
Which of the following are units for the magnetic moment? (There could be more than one correct choice.)

Question 61

Choose the one alternative that best completes the statement or answers the question.

Question 62

Choose the one alternative that best completes the statement or answers the question.

Question 63

Choose the one alternative that best completes the statement or answers the question.
Consider an ideal solenoid of length L, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the radius of the solenoid is doubled to 2b, but all
The other quantities remain the same, the magnetic field inside the solenoid will

A) become one-half as strong as initially.
B) remain the same.
C) become one-fourth as strong as initially.
D) become twice as strong as initially.
E) become four times as strong as initially.

Question 64

Choose the one alternative that best completes the statement or answers the question.
In a certain velocity selector consisting of perpendicular electric and magnetic fields, the charged particles move toward the east, and the magnetic field is directed to the north. What direction
Should the electric field point?

A) downward
B) toward the east
C) upward
D) toward the west
E) toward the south

Question 65

Write the word or phrase that best completes each statement or answers the question.

Question 66

Choose the one alternative that best completes the statement or answers the question.
A long straight wire has a constant current flowing to the right. A rectangular metal loop is situated above the wire, and also has a constant current flowing through it, as shown in the figure.
Which one of the following statements is true?

A) The net magnetic force on the rectangle is downward, and the net torque on it is zero.
B) The net magnetic force on the rectangle is zero, and the net torque on it is zero.
C) The net magnetic force on the rectangle is downward, and there is also a nonzero torque on the rectangle.
D) The net magnetic force on the rectangle is zero, but there is a nonzero torque on the rectangle.
E) The net magnetic force on the rectangle is upward, and there is also a nonzero torque on the rectangle.

Question 67

Write the word or phrase that best completes each statement or answers the question.

Question 68

Choose the one alternative that best completes the statement or answers the question.
When you double the number of windings in an ideal solenoid while keeping all other parameters (radius, length and current) fixed, the magnetic field at the center of the solenoid will

A) triple.
B) double.
C) be reduced by a factor of one-fourth.
D) quadruple.
E) be reduced by a factor of one-half.

Question 69

Choose the one alternative that best completes the statement or answers the question.
In a velocity selector consisting of perpendicular electric and magnetic fields, the speeds of the
charged particles passing through the selector are increased or decreased until they are equal to the
desired speed.

Question 70

Choose the one alternative that best completes the statement or answers the question.
A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current

A) points to the left.
B) circles the wire in a clockwise direction.
C) points directly away from you.
D) circles the wire in a counter-clockwise direction.

Question 71

Choose the one alternative that best completes the statement or answers the question.
A proton is projected with a velocity of 7.0 km/s into a magnetic field of 0.60 T perpendicular to the motion of the proton. What is the magnitude of the magnetic force that acts on the proton? (e =

Question 72

Choose the one alternative that best completes the statement or answers the question.
Consider an ideal solenoid of length L, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the length of the solenoid becomes twice as long
(to 2L), but all other quantities remained the same, the magnetic field inside the solenoid will

A) become one-half as strong as initially.
B) become twice as strong as initially.
C) become one-fourth as strong as initially.
D) remain the same.
E) become four times as strong as initially.

Question 73

Choose the one alternative that best completes the statement or answers the question.

Question 74

Choose the one alternative that best completes the statement or answers the question.
When a ferromagnetic material is placed in an external magnetic field, the net magnetic field of its magnetic domains becomes

A) smaller.
B) larger.
C) zero.

Question 75

Choose the one alternative that best completes the statement or answers the question.

Question 76

Choose the one alternative that best completes the statement or answers the question.
Which one of the following statements is correct?

A) When a current-carrying wire is in your left hand, with your thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.
B) When a current-carrying wire is in your right hand, with your thumb in the direction of the current, your fingers point opposite to the direction of the magnetic field lines.
C) When a current-carrying wire is in your right hand, with your thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.

Question 77

Write the word or phrase that best completes each statement or answers the question.

Question 78

Choose the one alternative that best completes the statement or answers the question.

Question 79

Choose the one alternative that best completes the statement or answers the question.
A vertical wire carries a current vertically downward. To the east of this wire, the magnetic field points

A) down.
B) north.
C) east.
D) south.

Question 80

Write the word or phrase that best completes each statement or answers the question.