Question 1

The magnetic domains in a magnetized piece of iron are characterized by which orientation?

Accepted Answer

A)  anti-parallel (opposite direction) to the magnetic axis 
B)  perpendicular to the magnetic axis 
C)  parallel to the magnetic axis 
D)  random 
A)  anti-parallel (opposite direction) to the magnetic axis 
B)  perpendicular to the magnetic axis 
C)  parallel to the magnetic axis 
D)  random C

Question 2

A copper wire of length 10 cm is in a magnetic field of 0.30 T. If it has a mass of 20 g, what minimum current through the wire would cause a magnetic force equal to its weight?

Accepted Answer

A)  4.9 A 
B)  6.5 A 
C)  2.0 A 
D)  1.3 A 
A)  4.9 A 
B)  6.5 A 
C)  2.0 A 
D)  1.3 A B

Question 3

A solenoid with 500 turns, 0.10 m long, carrying a current of 2.0 A and with a radius of 10 - 2 m will have what strength magnetic field at its center? (magnetic permeability in empty space µ0 = 4 $\pi$ * 10 - 7 T.m/A)

Accepted Answer

A)  31*10 - 4 T 
B)  1.3 *10 - 2 T 
C)  2.5 *10 - 2 T 
D)  62 *10 - 4 T 
A)  31*10 - 4 T 
B)  1.3 *10 - 2 T 
C)  2.5 *10 - 2 T 
D)  62 *10 - 4 T B

Question 4

When a magnetic field causes a charged particle to move in a circular path, the only quantity listed below which the magnetic force changes significantly as the particle goes around in a circle is the particle's:

Accepted Answer

A)  energy. 
B)  time to go around the circle once. 
C)  momentum. 
D)  radius for the circle. 
A)  energy. 
B)  time to go around the circle once. 
C)  momentum. 
D)  radius for the circle.

Question 5

A beam of electrons is sent in the positive x direction in a region with a uniform magnetic field B in the positive y direction and a uniform electric field E in the positive z direction. At which of the following speeds would the electrons be deflected in the positive z direction?

Accepted Answer

A)  v = E/B 
B)  There is no speed for which this will happen. 
C)  v  E/B 
A)  v = E/B 
B)  There is no speed for which this will happen. 
C)  v  E/B

Question 6

Geophysicists today generally attribute the existence of the Earth's magnetic field to which of the following?

Accepted Answer

A)  solar flares 
B)  iron ore deposits in the crust 
C)  currents within the liquid interior 
D)  nickel-iron deposits in the crust 
A)  solar flares 
B)  iron ore deposits in the crust 
C)  currents within the liquid interior 
D)  nickel-iron deposits in the crust

Question 7

A 2.0-m wire segment carrying a current of 0.60 A oriented parallel to a uniform magnetic field of 0.25 T experiences a force of what magnitude?

Accepted Answer

A)  0.30 N 
B)  6.7 N 
C)  0.15 N 
D)  zero 
A)  0.30 N 
B)  6.7 N 
C)  0.15 N 
D)  zero

Question 8

A proton moving with a speed of 6.0 *105 m/s perpendicular to a uniform magnetic field of 0.20 T will follow which of the paths described below? (qp = 1.6 *10-19 C and mp = 1.67 * 10-27 kg)

Accepted Answer

A)  a circular path of 1.6-cm radius 
B)  a circular path of 3.1-cm radius 
C)  a circular path of 6.3-cm radius 
D)  a straight line path 
A)  a circular path of 1.6-cm radius 
B)  a circular path of 3.1-cm radius 
C)  a circular path of 6.3-cm radius 
D)  a straight line path

Question 9

A proton, mass 1.67 * 10 - 27 kg and charge +1.6 *10 - 19 C, moves in a circular orbit perpendicular to a uniform magnetic field of 0.50 T. Find the time for the proton to make one complete circular orbit.

Accepted Answer

A)  8.7 *10 - 8 s 
B)  1.3 *10 - 7 s 
C)  9.8 *10 - 7 s 
D)  4.3 *10 - 8 s 
A)  8.7 *10 - 8 s 
B)  1.3 *10 - 7 s 
C)  9.8 *10 - 7 s 
D)  4.3 *10 - 8 s

Question 10

The magnetic force on a charged particle moving at a constant speed in a uniform magnetic field will be doubled when the angle between the velocity of the particle and the direction of the magnetic field changes from 25.0° to

Accepted Answer

A)  57.7°. 
B)  12.5°. 
C)  12.2°. 
D)  50.0°. 
A)  57.7°. 
B)  12.5°. 
C)  12.2°. 
D)  50.0°.

Question 11

A stationary positive charge +Q is located in a magnetic field B, which is directed toward the right as indicated. The direction of the magnetic force on Q is:

Accepted Answer

A)  toward the right. 
B)  up. 
C)  There is no magnetic force. 
D)  down. 
A)  toward the right. 
B)  up. 
C)  There is no magnetic force. 
D)  down.

Question 12

Assume that a uniform magnetic field is directed into this page. If a proton is released with an initial velocity directed from the bottom edge to the top edge of the page, which of the following describes the direction of the resultant force acting on the proton?

Accepted Answer

A)  into the page 
B)  to the left 
C)  to the right 
D)  out of the page 
A)  into the page 
B)  to the left 
C)  to the right 
D)  out of the page

Question 13

Two parallel wires carry the a current I in the same direction. Midway between these wires is a third wire, also parallel to the other two, which carries a current 0.5 I, but in the direction opposite from the first two wires. In which direction are the net forces on the outer wires?

Accepted Answer

A)  Both forces are toward the center wire. 
B)  Since the net forces are zero, there is no direction. 
C)  Both forces are away from the center wire. 
D)  Both forces on the two wires are in the same direction in space. 
A)  Both forces are toward the center wire. 
B)  Since the net forces are zero, there is no direction. 
C)  Both forces are away from the center wire. 
D)  Both forces on the two wires are in the same direction in space.

Question 14

Two insulated current-carrying straight wires of equal length are arranged in the lab so that Wire A carries a current northward and Wire B carries a current eastward, the wires crossing at their midpoints separated only by their insulation. Which of the statements below is true?

Accepted Answer

A)  There are no forces in this situation. 
B)  The net force on Wire B is southward. 
C)  There are forces, but the net force on each wire is zero. 
D)  The net force on Wire A is westward. 
A)  There are no forces in this situation. 
B)  The net force on Wire B is southward. 
C)  There are forces, but the net force on each wire is zero. 
D)  The net force on Wire A is westward.

Question 15

Two long parallel wires 40 cm apart are carrying currents of 10 A and 30 A in the same direction. What is the magnitude of the magnetic field halfway between the wires?

Accepted Answer

A)  4.0 * 10-5 T 
B)  1.0 * 10-5 T 
C)  3.0 * 10-5 T 
D)  2.0 *10-5 T 
A)  4.0 * 10-5 T 
B)  1.0 * 10-5 T 
C)  3.0 * 10-5 T 
D)  2.0 *10-5 T

Question 16

A proton moving at a speed of 3.8 *106 m/s cuts across the lines of a magnetic field at an angle of 40°. The strength of the field is 0.25 *10-4 T. What is the magnitude of the force acting on the proton? (qp = 1.6 *10-19 C)

Accepted Answer

A)  1.4 *10-17 N 
B)  2.3 * 10-17 N 
C)  9.8 *10-18 N 
D)  5.1 *10-18 N 
A)  1.4 *10-17 N 
B)  2.3 * 10-17 N 
C)  9.8 *10-18 N 
D)  5.1 *10-18 N

Question 17

There is a current I flowing in a clockwise direction in a square loop of wire that is in the plane of the paper. If the magnetic field B is toward the right, and if each side of the loop has length L, then the net magnetic torque acting on the loop is:

Accepted Answer

A)  IBL2. 
B)  2ILB. 
C)  ILB. 
D)  zero. 
A)  IBL2. 
B)  2ILB. 
C)  ILB. 
D)  zero.

Question 18

The magnetic pole of the Earth nearest the geographic South Pole corresponds to which of the following?

Accepted Answer

A)  a magnetic south pole 
B)  a magnetic Antarctic pole 
C)  a magnetic north pole 
D)  a magnetic arctic pole 
A)  a magnetic south pole 
B)  a magnetic Antarctic pole 
C)  a magnetic north pole 
D)  a magnetic arctic pole

Question 19

The magnetic force on a charged particle moving at a constant speed in a uniform magnetic field will be halved when the angle between the velocity of the particle and the direction of the magnetic field changes from 25.0° to

Accepted Answer

A)  50.0°. 
B)  12.5°. 
C)  57.7°. 
D)  12.2°. 
A)  50.0°. 
B)  12.5°. 
C)  57.7°. 
D)  12.2°.

Question 20

Two singly ionized isotopes, X and Y, of the same element move with the same speed perpendicular to a uniform magnetic field. Isotope X follows a path of radius 3.35 cm while isotope Y moves along a path 3.43 cm in radius. What is the ratio of the two isotope masses, mY/mX?

Accepted Answer

A)  0.977 
B)  0.954 
C)  1.05 
D)  1.02 
A)  0.977 
B)  0.954 
C)  1.05 
D)  1.02

Exam 20: Magnetic Fields and Forces

The magnetic domains in a magnetized piece of iron are characterized by which orientation?

A copper wire of length 10 cm is in a magnetic field of 0.30 T. If it has a mass of 20 g, what minimum current through the wire would cause a magnetic force equal to its weight?

A solenoid with 500 turns, 0.10 m long, carrying a current of 2.0 A and with a radius of 10 - 2 m will have what strength magnetic field at its center? (magnetic permeability in empty space µ0 = 4 π\piπ * 10 - 7 T.m/A)

When a magnetic field causes a charged particle to move in a circular path, the only quantity listed below which the magnetic force changes significantly as the particle goes around in a circle is the particle's:

A beam of electrons is sent in the positive x direction in a region with a uniform magnetic field B in the positive y direction and a uniform electric field E in the positive z direction. At which of the following speeds would the electrons be deflected in the positive z direction?

Geophysicists today generally attribute the existence of the Earth's magnetic field to which of the following?

A 2.0-m wire segment carrying a current of 0.60 A oriented parallel to a uniform magnetic field of 0.25 T experiences a force of what magnitude?

A proton moving with a speed of 6.0 *105 m/s perpendicular to a uniform magnetic field of 0.20 T will follow which of the paths described below? (qp = 1.6 *10-19 C and mp = 1.67 * 10-27 kg)

A proton, mass 1.67 * 10 - 27 kg and charge +1.6 *10 - 19 C, moves in a circular orbit perpendicular to a uniform magnetic field of 0.50 T. Find the time for the proton to make one complete circular orbit.

The magnetic force on a charged particle moving at a constant speed in a uniform magnetic field will be doubled when the angle between the velocity of the particle and the direction of the magnetic field changes from 25.0° to

A stationary positive charge +Q is located in a magnetic field B, which is directed toward the right as indicated. The direction of the magnetic force on Q is:

Assume that a uniform magnetic field is directed into this page. If a proton is released with an initial velocity directed from the bottom edge to the top edge of the page, which of the following describes the direction of the resultant force acting on the proton?

Two parallel wires carry the a current I in the same direction. Midway between these wires is a third wire, also parallel to the other two, which carries a current 0.5 I, but in the direction opposite from the first two wires. In which direction are the net forces on the outer wires?

Two insulated current-carrying straight wires of equal length are arranged in the lab so that Wire A carries a current northward and Wire B carries a current eastward, the wires crossing at their midpoints separated only by their insulation. Which of the statements below is true?

Two long parallel wires 40 cm apart are carrying currents of 10 A and 30 A in the same direction. What is the magnitude of the magnetic field halfway between the wires?

A proton moving at a speed of 3.8 *106 m/s cuts across the lines of a magnetic field at an angle of 40°. The strength of the field is 0.25 *10-4 T. What is the magnitude of the force acting on the proton? (qp = 1.6 *10-19 C)

There is a current I flowing in a clockwise direction in a square loop of wire that is in the plane of the paper. If the magnetic field B is toward the right, and if each side of the loop has length L, then the net magnetic torque acting on the loop is:

The magnetic pole of the Earth nearest the geographic South Pole corresponds to which of the following?

The magnetic force on a charged particle moving at a constant speed in a uniform magnetic field will be halved when the angle between the velocity of the particle and the direction of the magnetic field changes from 25.0° to

Two singly ionized isotopes, X and Y, of the same element move with the same speed perpendicular to a uniform magnetic field. Isotope X follows a path of radius 3.35 cm while isotope Y moves along a path 3.43 cm in radius. What is the ratio of the two isotope masses, mY/mX?

Introduction

Motion, Forces, and Newtons Laws

Forces and Motion in One Dimension

Forces and Motion in Two and Three Dimensions

Circular Motion and Gravitation

Work and Energy

Momentum, Impulse, and Collisions

Rotational Motion

Energy and Momentum of Rotational Motion

Fluids

Harmonic Motion and Elasticity

Waves

Sound

Temperature and Heat

Gases and Kinetic Theory

Thermodynamics

Electric Forces and Fields

Electric Potential

Electric Currents and Circuits

Magnetic Induction

Alternating-Current Circuits and Machines

Electromagnetic Waves

Geometrical Optics

Wave Optics

Applications of Optics

Relativity

Quantum Theory

Atomic Theory

Nuclear Physics

Physics in the 21st Century

Filters

A solenoid with 500 turns, 0.10 m long, carrying a current of 2.0 A and with a radius of 10 ^- ²m will have what strength magnetic field at its center? (magnetic permeability in empty space µ₀ = 4 $\pi$ * 10 ^- ⁷T.m/A)

A proton moving with a speed of 6.0 10⁵ m/s perpendicular to a uniform magnetic field of 0.20 T will follow which of the paths described below? (q_p = 1.6 10^-¹⁹ C and m_p = 1.67 * 10^-²⁷ kg)

A proton, mass 1.67 * 10 ^- ²⁷kg and charge +1.6 *10 ^- ¹⁹ C, moves in a circular orbit perpendicular to a uniform magnetic field of 0.50 T. Find the time for the proton to make one complete circular orbit.

A proton moving at a speed of 3.8 10⁶ m/s cuts across the lines of a magnetic field at an angle of 40°. The strength of the field is 0.25 10^-⁴ T. What is the magnitude of the force acting on the proton? (q_p = 1.6 *10^-¹⁹ C)

Two singly ionized isotopes, X and Y, of the same element move with the same speed perpendicular to a uniform magnetic field. Isotope X follows a path of radius 3.35 cm while isotope Y moves along a path 3.43 cm in radius. What is the ratio of the two isotope masses, m_Y/m_X?