Deck 27: Magnetism

Question 1

The earth's northern magnetic pole is located

A)near Tasmania.
B)near Antarctica.
C)at the North Pole.
D)at the South Pole.
E)in northern Canada.

Answer 1

in northern Canada.

Question 2

The figure below shows 2 bar magnets of the same size and the same strength. Which of the arrows labeled A to D correctly represents the direction of the magnetic field at a point located at the common origin of the arrows? (That point is at an equal distance from the two magnets.)

A)A
B)B
C)C
D)D
E)The field is oriented perpendicular to the figure into the page.

Answer 2

A

Question 3

A charged particle traveling opposite to a magnetic field does not experience a magnetic force.

Answer 3

True

Question 4

An electric current produces

A)a gravitational field.
B)an electric field.
C)a magnetic field.
D)an electromagnetic field.
E)a universal field.

Question 5

The figure below shows 3 bar magnets of equal sizes and equal strengths. At which of the points labeled A to E is the magnetic field approximately equal to zero? (Points B and C are at equal distances from the magnets.)

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

Question 6

A wire carrying a current that placed in a magnetic field will experience a maximum force if the angle between the direction of the current and the direction of the magnetic field is 60°.

Question 7

Magnetic field lines can never cross one another.

Question 8

In a velocity selector having electric field E and magnetic field B, the velocity selected for positively charged particles is v = E/B. The formula is the same for a negatively charged particles.

Question 9

A rectangular coil carrying a current in a magnetic field will experience a net torque that will cause the coil to rotate in that field, if the field is not along the coil axis.

Question 10

The magnetic field unlike the electric field is continuous.

Question 11

At a given location the direction of the magnetic field is the direction that the north pole of a compass points when placed at that location.

Question 12

Which of the following statements is correct?

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

Question 13

If the north poles of two bar magnets are brought close to each other, the magnets will

A)attract.
B)repel.

Question 14

If the south pole of one bar magnet is brought near the north pole of a second bar magnet, the two magnets will

A)attract.
B)repel.

Question 15

A wire of length L carrying a current I is placed in a magnetic field. The direction of the magnetic field is opposite the direction of the current. In this situation, the wire experiences a maximum force.

Question 16

There is no such thing as a dc electric motor.

Question 17

Cutting a bar magnet near its north end results in a smaller mostly north pole magnet and a larger mostly south pole magnet.

Question 18

In using a magnet to find north, the term "declination" represents

A)the degree of weakness of the magnetic field.
B)the angle above the horizontal of the earth's magnetic field.
C)another term for "angle of dip."
D)the angle below the horizontal of the earth's magnetic field.
E)not given

Question 19

A current carrying wire placed in a magnetic field perpendicular to the wire experiences a maximum force.

Question 20

The earth's northern magnetic pole acts like

A)it has negative charge.
B)it has positive charge.
C)it has no charge.
D)the north pole of a magnet.
E)the south pole of a magnet.

Question 21

A proton is moving at an angle of 80° to a uniform magnetic field. What is the relationship between the direction of the force on the proton and the direction of the magnetic field?

A)parallel to the magnetic field
B)at an angle of 10° to the magnetic field
C)at an angle of 80° to the magnetic field
D)at an angle of 180° to the magnetic field
E)perpendicular to the magnetic field

Question 22

An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, what is the direction of the magnetic field in this region?

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

Question 23

The force on a current-carrying wire in a magnetic field is equal to zero when

A)the current is parallel to the field lines.
B)the current is at a 30° angle with respect to the field lines.
C)the current is at a 45° angle with respect to the field lines.
D)the current is at a 60° angle with respect to the field lines.
E)the current is perpendicular to the field lines.

Question 24

A current carrying loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, outside the loop? The magnetic field

A)circles the loop in a clockwise direction.
B)circles the loop in a counterclockwise direction.
C)points straight up.
D)points straight down.
E)points toward the east.

Question 25

A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current

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

Question 26

A square loop of wire carrying a current in a clockwise direction lies in the plane of the paper. The magnetic field inside the loop is directed

A)out of the paper everywhere.
B)out of the paper near the wire, but into the paper elsewhere.
C)into the paper everywhere.
D)into the paper near the wire but out of the paper elsewhere.
E)not given

Question 27

A wire is carrying current vertically downward. What is the direction of the force due to Earth's magnetic field on the wire?

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

Question 28

Which of the following is correct?

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

Question 29

The force on a current-carrying wire in a magnetic field is the strongest when

A)the current is parallel to the field lines.
B)the current is at a 30° angle with respect to the field lines.
C)the current is at a 45° angle with respect to the field lines.
D)the current is at a 60° angle with respect to the field lines.
E)the current is perpendicular to the field lines.

Question 30

A vertical wire carries a current straight up in a region where the magnetic field vector points due north. What is the direction of the resulting force on this current?

A)down
B)north
C)south
D)east
E)west

Question 31

The direction of the force on a current-carrying wire in a magnetic field is described by which of the following?

A)parallel to the current only
B)parallel to the magnetic field only
C)perpendicular to the current only
D)perpendicular to the magnetic field only
E)perpendicular to both the current and the magnetic field

Question 32

A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle's weight, the particle will

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

Question 33

FIGURE 27-1
When the switch is closed in the circuit shown in the sketch in Fig. 27-1, the wire between the poles of the horseshoe magnet deflects upward. From this you can conclude that the left end of the magnet is

A)not contributing to the wire's deflection.
B)a north magnetic pole.
C)a south magnetic pole.
D)a magnetic monopole.
E)a magnetic dipole.

Question 34

A proton, moving north, enters a magnetic field of a certain strength. Because of this field the proton curves downward. What is the direction of the magnetic field?

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

Question 35

An electron, moving south, enters a magnetic field of certain strength. Because of this field the electron curves upward. What is the direction of the magnetic field?

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

Question 36

A vertical wire carries a current straight down. To the east of this wire, the magnetic field points

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

Question 37

FIGURE 27-2
A horizontal, long current-carrying wire is hanging from a vertical thread. The current is oriented into the plane of Fig. 27-2 shown above. A uniform magnetic field is applied and the wire is pulled away from the vertical. Which of the arrows labeled A to D correctly indicate the direction of the magnetic field?

A)A
B)B
C)C
D)D
E)The magnetic field is oriented into the plane of the picture.

Question 38

FIGURE 27-3
Fig. 27-3 shows a small positive charge q moving toward a long current-carrying wire. Which of the arrows labeled A to D correctly represents the direction of the magnetic force applied on the charge?

A)A
B)B
C)C
D)D
E)The force points in a direction perpendicular to the plane of the figure.

Question 39

A current carrying circular loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, inside the loop? The magnetic field

A)circles the loop in a clockwise direction.
B)circles the loop in a counterclockwise direction.
C)points straight up.
D)points straight down.
E)points toward the east.

Question 40

A proton, moving east, enters a magnetic field of a certain strength. Because of this field the proton curves downward. What is the direction of the magnetic field?

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

Question 41

The sign of the charge carriers in a current can be determined using the

A)Hall effect.
B)drift velocity.
C)oil drop experiment.
D)mass spectrometer.
E)not given

Question 42

An alpha particle is moving at a speed of 5 × 10⁵ m/s in a direction perpendicular to a uniform magnetic field of strength 4 × 10^-2 T. The charge on an alpha particle is 3.2 × 10^-19 C and its mass is 6.6 × 10^-27 kg. (a) The radius of the path of the alpha particle is
(b) The time it takes the alpha particle to complete one revolution around its path is

Question 43

An alpha particle is moving at a speed of 5 × 10⁵ m/s in a direction perpendicular to a uniform magnetic field of strength 4 × 10^-2 T. The charge on an alpha particle is 3.2 × 10^-19 C and its mass is 6.6 × 10^-27 kg. (a) As the alpha particle moves, its velocity is directed
(b) The magnitude of the force on the alpha particle is

Question 44

An electron, moving west, enters a magnetic field of a certain strength. Because of this field the electron curves upward. What is the direction of the magnetic field?

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

Question 45

A force = F₀ - F₀ (where F₀ > 0) acts on a moving charge that enters a magnetic field = B₀
(B₀ > 0). Which of the following expressions correctly represents the direction of the velocity of the charge?

A) = v₀
+ v₀


B) = v₀
- v₀


C) = v₀
+ v₀


D) = v₀
+ v₀


E) = -v₀
- v₀

Question 46

A 2.0-m wire carrying a current of 0.60 A is oriented parallel to a uniform magnetic field of 0.50 T. What is the magnitude of the force it experiences?

A)zero
B)0.15 N
C)0.30 N
D)0.50 N
E)0.60 N

Question 47

Two equal charges enter a magnetic field oriented along the positive z-axis. The particles are initially at the origin. Charge A has a velocity = v₀ + v₀ + v₀ and charge B has a velocity = 2v₀ + + . In both cases the path of the motion will be a helix. What will be the difference in the patterns of motion?

A)The helix for B will have wider circles spread further apart.
B)The helix for B will have wider circles closer to each other.
C)The helix for B will have same-size circles as A, but spread further apart.
D)The helix for B will have same-size circles as A, but grouped closer to each other.
E)Both helixes will look the same.

Question 48

A proton, moving west, enters a magnetic field of a certain strength. Because of this magnetic field the proton curves upward. What is the direction of this magnetic field?

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

Question 49

In a mass spectrometer a particle of mass m and charge q is accelerated through a potential difference V and allowed to enter a magnetic field B, where it is deflected in a semi-circular path of radius R. The magnetic field is uniform and oriented perpendicular to the velocity of the particle. Derive an expression for the mass of the particle in terms of B, q, V, and R.

A)qB²R²/V
B)qB²R²/(2V)
C)q²B²R²/V
D)q²B²R²/(2V)
E)qB²R²/(V²)

Question 50

FIGURE 27-9
A wire in the shape of an "M" lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E. It is placed in a uniform magnetic field of 0.75 T in the same plane, directed as shown on the right side of Fig. 27-9. The figure indicates the dimensions of the wire.
(a) What is the magnitude and direction of the force acting on section AB of this wire?
(b) What is the magnitude and direction of the force acting on section BC of this wire?
(c) What is the magnitude and direction of the force acting on section CD of this wire?
(d) What is the magnitude and direction of the force acting on section DE of this wire?
(e) What is the magnitude and direction of the force acting on the wire

Question 51

What fundamental fact underlies the operation of essentially all electric motors?

A)Opposite electric charges attract and like charges repel.
B)A current-carrying conductor placed perpendicular to a magnetic field will experience a force.
C)Alternating current and direct current are both capable of doing work.
D)Iron is the only element that is magnetic.
E)A magnetic north pole carries a positive electric charge, and a magnetic south pole carries a negative electric charge.

Question 52

FIGURE 27-5
A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Fig. 27-5. If there is no current flowing through the coil, what is the force acting on section AB of the coil?

A)ILB sinθ
B)ILB cos θ
C)ILB
D)0 N
E)None of the other answers is correct.

Question 53

A fifteen turn rectangular loop of wire of width 10 cm and length 20 cm has a current of 2.5 A flowing through it. Two sides of the loop are oriented parallel to a uniform magnetic field of strength 0.037 T, the other two sides being perpendicular to the magnetic field.
(a) The torque on the loop is
(b) The magnetic moment of this coil is

Question 54

An electron moves with a speed of 8.0 × 10⁶ m/s along the +x axis. It enters a region where there is a magnetic field of 2.5 T, directed at an angle of 60° to the +x axis and lying in the xy plane.
(a) Calculate the magnitude of the magnetic force on the electron.
(b) Calculate the magnitude of the acceleration of the electron.

Question 55

FIGURE 27-6
A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Fig. 27-6. If there is a current I flowing through this coil, what is the force acting on section BC of this coil?

A)ILB/2
B)0 N
C)ILB sinθ
D)ILB cos θ
E)ILB

Question 56

A charged particle is moving with speed v perpendicular to a uniform magnetic field. A second identical charged particle is moving with speed 2v perpendicular to the same magnetic field. The frequency of revolution of the first particle is f. The frequency of revolution of the second particle is

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

Question 57

FIGURE 27-8
A voltmeter is used to measure the voltage across a Hall strip conducting a current in the negative y-direction as shown in Fig. 27-8. The charge carriers are known to be positive in this strip. What is the direction of the magnetic field used in this experiment if the reading on the voltmeter is negative when the probes are connected as shown?

A)negative x direction
B)positive x direction
C)positive z direction
D)negative z direction
E)positive y direction

Question 58

FIGURE 27-7
A Hall effect experiment is set-up with a conducting strip placed inside a magnetic field. A voltmeter is used to measure the voltage in the direction perpendicular to the direction of the current through the strip, as shown in Fig. 27-7. A current I runs in the positive y-direction, while the magnetic field is oriented in the positive z-direction. If the reading of the voltmeter is positive when the wires are connected to its terminals as shown below, what is the sign of the charge carriers in this strip?

A)negative
B)negative on the edges and positive in the middle of the strip
C)could be either one
D)positive on the edges and negative in the middle of the strip
E)positive

Question 59

FIGURE 27-4
Three particles travel through a region of space where the magnetic field is out of the page, as shown in Fig. 27-4. The electric charge of each of the three particles is, respectively,

A)1 is neutral, 2 is negative, and 3 is positive.
B)1 is neutral, 2 is positive, and 3 is negative.
C)1 is positive, 2 is neutral, and 3 is negative.
D)1 is positive, 2 is negative, and 3 is neutral.
E)1 is negative, 2 is neutral, and 3 is positive.

Question 60

The maximum torque on a current carrying loop occurs when the angle between the loop's magnetic moment and the magnetic field vector is

A)0°
B)45°
C)90°
D)180°
E)none of the given answers

Question 61

A proton moving with a velocity of 4.0 × 10⁴ m/s along the +y-axis enters a magnetic field of 0.20 T directed towards the -x-axis. What is the magnitude force acting on the proton?

A)8.0 × 10^-15 N
B)3.9 × 10^-15 N
C)2.6 × 10^-15 N
D)0 N
E)1.3 × 10^-15 N

Question 62

A force =( 6 × 10^-3 N ) - (4 × 10^-3 N) - (8 × 10^-3 N) is acting on a charge q = 2 × 10^-9 C moving inside a uniform magnetic field with a velocity = (2 × 10⁶ m/s) + (3 × 10⁶ m/s) . Calculate the components of the magnetic field knowing that the x-component of the field is equal to zero.

A) =- (4T) + (0.5 T)
B) =- (3T) + (2T)
C) = - (2 T) + (1 T)
D) = (2 T) - (1 T)
E) = (4 T) - (0.5 T)

Question 63

A wire carries a current of 11.4 A in a direction that makes an angle of 11.4° with a magnetic field of magnitude 11.4 × 10^-3 T. The magnitude of the force on 11.4 cm of this wire is

A)1.48 × 10^-2 N.
B)0.013 N.
C)11.4 × 10^-3 N.
D)2.93 × 10^-3 N.
E)0.130 N.

Question 64

A 1.0-m long wire is carrying a certain amount of current. The wire is placed perpendicular to a magnetic field of strength 0.20 T. If the wire experiences a force of 0.60 N, what is the magnitude of the current moving through the wire?

A)2.0 A
B)1.0 A
C)3.0 A
D)4.0 A
E)5.0 A

Question 65

FIGURE 27-10
A horizontal, long current-carrying wire is hanging from a vertical thread. The current is oriented into the plane of Fig. 27-10 shown above. A uniform magnetic field B = 0.4 T is applied along the negative y-axis and the wire is pulled and angle θ away from the vertical by a magnetic force. The wire has a length L = 80 cm, a mass m = 50 g and carries a current I = 0.3A. What is the value of the angle θ?

A)25°
B)67°
C)3°
D)45°
E)11°

Question 66

A stationary proton is in a uniform magnetic field of 0.20 T. What is the magnitude of the magnetic force on the proton?

A)zero
B)1.6 × 10^-20 N
C)3.2 × 10^-20 N
D)1.6 × 10^-21 N
E)3.2 × 10^-21 N

Question 67

A proton moving eastward with a velocity of 5.0 × 10³ m/s enters a magnetic field of 0.20 T pointing northward. What is the magnitude and direction of the force that acts on the proton?

A)0 N
B)1.6 × 10^-16 N upwards
C)1.6 × 10^-16 N downwards
D)1.1 × 10^-16 N eastwards
E)4.4 × 10^-16 N westwards

Question 68

An electron traveling due north with speed 4.0 × 10⁵ m/s enters a region where the Earth's magnetic field has the magnitude 5.0 × 10^-5 T and is directed downward at 45° below horizontal. What force acts on the electron?

A)2.3 × 10^-18 N
B)3.2 × 10^-18 N
C)2.3 × 10^-19 N
D)3.2 × 10^-19 N
E)2.3 × 10^-20 N

Question 69

A wire of a certain length is carrying a current of 2.0 A. It is placed at an angle of 60° with respect to a magnetic field of strength 0.20 T. If the wire experiences a force of 0.40 N, what is the length of the wire?

A)1.0 m
B)1.2 m
C)1.4 m
D)1.6 m
E)1.8 m

Question 70

A wire of a certain length, carrying a current of 2.0 A, is placed perpendicular to a magnetic field of strength 0.20 T. If the wire experiences a force of 0.40 N what is the length of the wire?

A)2.0 m
B)3.0 m
C)1.0 m
D)20 m
E)40 m

Question 71

A current is flowing in a wire in direction 3 + 4 where the direction of the magnetic field is 5 + 12 . The force on the wire is

A)0.78 - 0.58
+ 0.24
.
B)0.78 + 0.58
+ 0.24
.
C)0.78 + 0.58
- 0.24
.
D) .
E)0.71( +
).

Question 72

A 2-m long wire is carrying a current of 2 A. The wire is placed at an angle of 60° with respect to a magnetic field. If the wire experiences a force of 0.2 N, what is the strength of the magnetic field?

A)0.02 T
B)0.03 T
C)0.04 T
D)0.05 T
E)0.06 T

Question 73

An electron moves with a speed of 3.0 × 10⁴ m/s perpendicular to a uniform magnetic field of 0.40 T. What is the magnitude of the magnetic force on the electron?

A)4.8 × 10^-14 N
B)1.9 × 10^-15 N
C)5 × 10^-20 N
D)2.2 × 10^-24 N
E)zero

Question 74

A proton moving with a velocity of 4.0 × 10⁴ m/s enters a magnetic field of 0.20 T. If the angle between the velocity of the proton and the direction of the magnetic field is 60°, what is the magnitude of the force on the proton?

A)1.8 × 10^-15 N
B)0.60 × 10^-15 N
C)1.1 × 10^-15 N
D)2.2 × 10^-15 N
E)3.3 × 10^-15 N

Question 75

A straight wire 20 cm long, carrying a current of 4 A, is in a uniform magnetic field of 0.6 T. What is the force on the wire when it is at an angle of 30° with respect to the field?

A)0.2 N
B)0.3 N
C)0.4 N
D)0.5 N
E)0.6 N

Question 76

A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to cancel the weight of the rod?

A)1.2 A
B)2.5 A
C)4.9 A
D)7.6 A
E)9.8 A

Question 77

A proton is projected with a velocity of 7.0 × 10³ m/s into a magnetic field of 0.60 T perpendicular to the motion of the proton. What is the force that acts on the proton?

A)0 N
B)3.4 × 10^-16 N
C)4.2 × 10^-16 N
D)13 × 10^-16 N
E)6.7 × 10^-16 N

Question 78

A wire carrying a 2-A current is placed at an angle of 60° with the respect to a magnetic field of strength 0.2 T. If the length of the wire is 0.6 m what is the magnitude of the magnetic force acting on the wire?

A)0.4 N
B)0.2 N
C)0.6 N
D)0.8 N
E)1.0 N

Question 79

A wire, 0.60 m in length, is carrying a current of 2.0 A and is placed at a certain angle with respect to the magnetic field of strength 0.30 T. If the wire experiences a force of 0.18 N, what angle does the wire make with respect to the magnetic field?

A)20°
B)25°
C)30°
D)35°
E)60°

Question 80

A charge q = 3 × 10^-6 C of mass m = 2 × 10^-6 kg, and speed v = 5 × 10⁶ m/s enters a uniform magnetic field. The mass experiences an acceleration a = 3 × 10⁴ m/s². What is the minimum magnetic field that would produce such an acceleration?

A)0.1 T
B)0.004 T
C)0.001 T
D)0.01 T
E)0.04 T