PHYSICS CHAPTER 28-33 PRACTICE
QUESTIONS AND ANSWERS
ANSWER KEY ON LAST PAGE
1. The magnetic force on a charged particle is in the direction of its velocity if:
A) it is moving in the direction of the field
B) it is moving opposite to the direction of the field
C) it is moving perpendicular to the field
D) it is moving in some other direction
E) never
2. A proton (charge e), traveling perpendicular to a magnetic field, experiences the same
force as an alpha particle (charge 2e) which is also traveling perpendicular to the
same field. The ratio of their speeds, vproton/valpha is:
A) 0.5
B) 1
C) 2
D) 4
E) 8
3. At one instant an electron (charge = –1.6 × 10–19 C) is moving in the xy plane, the
components of its velocity being vx = 5 × 105 m/s and vy = 3 × 105 m/s. A magnetic field
of 0.8 T is in the positive x direction. At that instant the magnitude of the magnetic
force on the electron is:
A) 0
B) 3.8 × 10–14 N
C) 5.1 × 10–14 N
D) 6.4 × 10–14 N
E) 7.5 × 10–14 N
4. An electron is launched with velocity ² in a uniform magnetic field 4. The angle
𝜃 between ² and 4 is between 0 and 90o. As a result, the electron follows a helix,
its velocity vector ² returning to its initial value in a time interval of:
A) 2πm/eB
B) 2πmv/eB
C) 2πmv sin𝜃 /eB
D) 2πmv cos𝜃 /eB
E) none of these
,PHYSICS CHAPTER 28-33 PRACTICE
QUESTIONS AND ANSWERS
5. An electron is travelling in the positive x direction. A uniform electric field ® is in
the negative y direction. If a uniform magnetic field with the appropriate magnitude
and direction also exists in the region, the total force on the electron will be zero. The
appropriate direction for the magetic field is:
A) the positive y direction
B) the negative y direction
C) into the page
D) out of the page
E) the negative x direction
6. A cyclotron operates with a given magnetic field and at a given frequency. If R denotes
the radius of the final orbit, the final particle energy is proportional to:
A) 1/R
B) R
C) R2
D) R3
E) R4
7. The figure shows a uniform magnetic field 4 directed to the left and a wire carrying
a current into the page. The magnetic force acting on the wire is:
A) toward the top of the page
B) toward the bottom of the page
C) toward the left
D) toward the right
E) zero
,PHYSICS CHAPTER 28-33 PRACTICE
QUESTIONS AND ANSWERS
8. The units of magnetic dipole moment are:
A) ampere
B) ampere meter
C) ampere meter2
D) ampere/meter
E) ampere/meter2
9. The magnetic dipole moment of a current-carrying loop of wire is in the positive z
direction. If a uniform magnetic field is in the positive x direction the magnetic
torque on the loop is:
A) 0
B) in the positive y direction
C) in the negative y direction
D) in the positive z direction
E) in the negative z direction
10. The magnitude of the magnetic field at point P, at the center of the semicircle shown,
is given by:
A) 20i/R2
B) 0i/2𝜋R
C) 0i/4𝜋R
D)
0i/2R
E)
0i/4R
11. The magnetic field a distance 2 cm from a long straight current-carrying wire is 2.0
×10-5 T. The current wire is:
A) 0.16 A
B) 1.0 A
C) 2.0 A
D) 4.0 A
E) 25 A
, PHYSICS CHAPTER 28-33 PRACTICE
QUESTIONS AND ANSWERS
Page 3
QUESTIONS AND ANSWERS
ANSWER KEY ON LAST PAGE
1. The magnetic force on a charged particle is in the direction of its velocity if:
A) it is moving in the direction of the field
B) it is moving opposite to the direction of the field
C) it is moving perpendicular to the field
D) it is moving in some other direction
E) never
2. A proton (charge e), traveling perpendicular to a magnetic field, experiences the same
force as an alpha particle (charge 2e) which is also traveling perpendicular to the
same field. The ratio of their speeds, vproton/valpha is:
A) 0.5
B) 1
C) 2
D) 4
E) 8
3. At one instant an electron (charge = –1.6 × 10–19 C) is moving in the xy plane, the
components of its velocity being vx = 5 × 105 m/s and vy = 3 × 105 m/s. A magnetic field
of 0.8 T is in the positive x direction. At that instant the magnitude of the magnetic
force on the electron is:
A) 0
B) 3.8 × 10–14 N
C) 5.1 × 10–14 N
D) 6.4 × 10–14 N
E) 7.5 × 10–14 N
4. An electron is launched with velocity ² in a uniform magnetic field 4. The angle
𝜃 between ² and 4 is between 0 and 90o. As a result, the electron follows a helix,
its velocity vector ² returning to its initial value in a time interval of:
A) 2πm/eB
B) 2πmv/eB
C) 2πmv sin𝜃 /eB
D) 2πmv cos𝜃 /eB
E) none of these
,PHYSICS CHAPTER 28-33 PRACTICE
QUESTIONS AND ANSWERS
5. An electron is travelling in the positive x direction. A uniform electric field ® is in
the negative y direction. If a uniform magnetic field with the appropriate magnitude
and direction also exists in the region, the total force on the electron will be zero. The
appropriate direction for the magetic field is:
A) the positive y direction
B) the negative y direction
C) into the page
D) out of the page
E) the negative x direction
6. A cyclotron operates with a given magnetic field and at a given frequency. If R denotes
the radius of the final orbit, the final particle energy is proportional to:
A) 1/R
B) R
C) R2
D) R3
E) R4
7. The figure shows a uniform magnetic field 4 directed to the left and a wire carrying
a current into the page. The magnetic force acting on the wire is:
A) toward the top of the page
B) toward the bottom of the page
C) toward the left
D) toward the right
E) zero
,PHYSICS CHAPTER 28-33 PRACTICE
QUESTIONS AND ANSWERS
8. The units of magnetic dipole moment are:
A) ampere
B) ampere meter
C) ampere meter2
D) ampere/meter
E) ampere/meter2
9. The magnetic dipole moment of a current-carrying loop of wire is in the positive z
direction. If a uniform magnetic field is in the positive x direction the magnetic
torque on the loop is:
A) 0
B) in the positive y direction
C) in the negative y direction
D) in the positive z direction
E) in the negative z direction
10. The magnitude of the magnetic field at point P, at the center of the semicircle shown,
is given by:
A) 20i/R2
B) 0i/2𝜋R
C) 0i/4𝜋R
D)
0i/2R
E)
0i/4R
11. The magnetic field a distance 2 cm from a long straight current-carrying wire is 2.0
×10-5 T. The current wire is:
A) 0.16 A
B) 1.0 A
C) 2.0 A
D) 4.0 A
E) 25 A
, PHYSICS CHAPTER 28-33 PRACTICE
QUESTIONS AND ANSWERS
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