Practice Quiz 7
Figure 1
1) A rectangular loop of wire, with dimensions shown in Figure 1, carries a current of 2 A and is placed in a
magnetic field of 0.8 T. The wire rotates in the magnetic field and at one point it is perpendicular to the magnetic
field. What is the magnitude of the torque acting on the wire?
A) 0 Nm
B) 1 Nm
C) 2 Nm
D) 4 Nm
Answer: B
2) A rectangular loop of wire carrying a 4.0-A current and with certain dimensions is placed in a magnetic field of
0.60 T. The magnitude of the torque acting on this wire when it makes a 60° angle with the field is 1.1 Nm. What is
the area of this wire?
A) 0.40 m2
B) 0.26 m2
C) 0.80 m2
D) 0.53 m2
Answer: D
Figure 2
3) A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown
in Figure 2. 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
Answer: B
Figure 3
4) A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown
in Figure 3. If there is a current I flowing through this coil, what is the force acting on section AB of this coil?
A) ILB sinθ
B) ILB
C) 0 N
D) ILB/2
Answer: B
5) 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
Answer: B
6) An electron moving perpendicular to a magnetic field of 2.2 × 10-2 T moves in a circle of certain radius. If the
electron is moving with a speed of 1.5 × 107 m/s, what is the radius of the circle?
A) 1.5 × 10-3 m
B) 2.2 × 10-3 m
C) 3.9 × 10-4 m/s
D) 3.9 × 10-3 m/s
Answer: D
7) 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) 3.9 × 10-15 N
B) 2.6 × 10-15 N
C) 0 N
D) 1.3 × 10-15 N
Answer: D
8) 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) towards the west
Answer: A
9) 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) towards the west
Answer: A
10) Which of the following statements is correct?
A) Earth's north pole is magnetic north.
B) The north pole of a magnet points towards the Earth's north pole.
C) The SI unit of the magnetic field is the gauss.
D) Like poles of a magnet attract each other and unlike poles repel.
Answer: B
11) Which of the following represents the SI unit of magnetic field?
A) N/(C m/s)
B) N A/m
C) N C/(m/s)
D) N m/A
Answer: A
12) A +2-µC charge is at rest in a magnetic field of 2 T pointing along the +x-axis. What is the force acting on this
charge in the magnetic field?
A) -4 µN
B) +4 µN
C) +2 µN
D) 0 N
Answer: D
13) 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) 13 × 10-16 N
D) 6.7 × 10-16 N
Answer: D
14) 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) 3.9 × 10-15 N
B) 2.6 × 10-15 N
C) 0 N
D) 1.3 × 10-15 N
Answer: D
15) 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) 3.9 × 10-15 N
B) 2.6 × 10-15 N
C) 0 N
D) 1.3 × 10-15 N
Answer: D