Question 1

A proton travels through a potential of 1.0 kV and then moves into a magnetic field of 0.040 T. What is the radius of the proton's resulting orbit?

Accepted Answer

A) 0.080 m 
B) 0.11 m 
C) 0.14 m 
D) 0.17 m 
E) 0.19 m 
A) 0.080 m 
B) 0.11 m 
C) 0.14 m 
D) 0.17 m 
E) 0.19 m B

Question 2

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

Accepted Answer

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

Question 3

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

Accepted Answer

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. 
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. E

Question 4

In a Hall experiment a conducting strip of thickness d = 100 μm is placed in a magnetic field B = 0.0 5 T. The magnetic field is perpendicular to the direction of the strip along which there is a 10-A current. What is the Hall voltage measured across the strip if the charge carrier density is 2.5 × 1028/m3 in this material?

Accepted Answer

A) 1.3 μV 
B) 2.5 μV 
C) 0.72 μV 
D) 6.2 μV 
E) 4.2 μV 
A) 1.3 μV 
B) 2.5 μV 
C) 0.72 μV 
D) 6.2 μV 
E) 4.2 μV

Question 5

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

Accepted Answer

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 
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 6

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?

Accepted Answer

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

Question 7

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?

Accepted Answer

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

Question 8

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?

Accepted Answer

A) 20° 
B) 25° 
C) 30° 
D) 35° 
E) 60° 
A) 20° 
B) 25° 
C) 30° 
D) 35° 
E) 60°

Question 9

A loop of diameter d = 12 cm, carrying a current I = 0.4 A is placed inside a magnetic field   = (0.2 T)   + (0.4 T)   . The normal to the loop is parallel to the unit vector   . What is the potential energy of the loop?

Accepted Answer

A) -4.5 × 10-4 J 
B) +9.0 × 10-4 J 
C) -9.0 × 10-4 J 
D) -2.3 × 10-4 J 
E) +4.5 × 10-4 J 
A) -4.5 × 10-4 J 
B) +9.0 × 10-4 J 
C) -9.0 × 10-4 J 
D) -2.3 × 10-4 J 
E) +4.5 × 10-4 J

Question 10

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?

Accepted Answer

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

Question 11

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?

Accepted Answer

A) 25° 
B) 67° 
C) 3° 
D) 45° 
E) 11° 
A) 25° 
B) 67° 
C) 3° 
D) 45° 
E) 11°

Question 12

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

Accepted Answer

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

Question 13

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.)

Accepted Answer

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

Question 14

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

Accepted Answer

(a) 0.26 m

Question 15

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?

Accepted Answer

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 
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 16

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

Accepted Answer

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. 
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 17

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

Accepted Answer

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 
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 18

A proton is moving at a speed of 3.2 × 106 m/s at an angle of 80° to a uniform magnetic field of strength 1.5 × 10-4 T. What is the distance moved by the proton along the spiral path as it completes one revolution? (This distance is called the "pitch" of the helix.)

Accepted Answer

A) 1370 m 
B) 1390 m 
C) 240 m 
D) 220 m 
E) cannot be determined 
A) 1370 m 
B) 1390 m 
C) 240 m 
D) 220 m 
E) cannot be determined

Question 19

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,

Accepted Answer

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. 
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 20

A circular loop of wire of cross-sectional area 0.12 m2 consists of 200 turns, each carrying 0.50 A. It is placed in a magnetic field of 0.050 T oriented at 30° to the plane of the loop. What torque acts on the loop?

Accepted Answer

A) 0.25 m∙N 
B) 0.52 m∙N 
C) 2.5 m∙N 
D) 5.2 m∙N 
E) 25 m∙N 
A) 0.25 m∙N 
B) 0.52 m∙N 
C) 2.5 m∙N 
D) 5.2 m∙N 
E) 25 m∙N

Exam 27: Magnetism

A proton travels through a potential of 1.0 kV and then moves into a magnetic field of 0.040 T. What is the radius of the proton's resulting orbit?

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

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

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

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 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 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 loop of diameter d = 12 cm, carrying a current I = 0.4 A is placed inside a magnetic field = (0.2 T) + (0.4 T) . The normal to the loop is parallel to the unit vector . What is the potential energy of the loop?

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

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.)

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?

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

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

A proton is moving at a speed of 3.2 × 106 m/s at an angle of 80° to a uniform magnetic field of strength 1.5 × 10-4 T. What is the distance moved by the proton along the spiral path as it completes one revolution? (This distance is called the "pitch" of the helix.)

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 circular loop of wire of cross-sectional area 0.12 m2 consists of 200 turns, each carrying 0.50 A. It is placed in a magnetic field of 0.050 T oriented at 30° to the plane of the loop. What torque acts on the loop?

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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 proton is moving at a speed of 3.2 × 10⁶ m/s at an angle of 80° to a uniform magnetic field of strength 1.5 × 10^-4 T. What is the distance moved by the proton along the spiral path as it completes one revolution? (This distance is called the "pitch" of the helix.)

A circular loop of wire of cross-sectional area 0.12 m² consists of 200 turns, each carrying 0.50 A. It is placed in a magnetic field of 0.050 T oriented at 30° to the plane of the loop. What torque acts on the loop?