Question 1

The current is from left to right in the conductor shown. The magnetic field is into the page and point S is at a higher potential than point T. The charge carriers are:

Accepted Answer

A)  positive 
B)  negative 
C)  neutral 
D)  absent 
E)  moving near the speed of light 
A)  positive 
B)  negative 
C)  neutral 
D)  absent 
E)  moving near the speed of light

Question 2

An electron moves in the negative x direction, through a uniform magnetic field that is in the negative y direction. The magnetic force on the electron is:

Accepted Answer

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

Question 3

In a certain mass spectrograph, an ion beam passes through a velocity filter consisting of mutually perpendicular fields and . The beam then enters a region of another magnetic field perpendicular to the beam. The radius of curvature of the resulting ion beam is proportional to:

Accepted Answer

A)  EB'/B 
B)  EB/B' 
C)  BB'/E 
D)  B/EB' 
E)  E/BB' 
A)  EB'/B 
B)  EB/B' 
C)  BB'/E 
D)  B/EB' 
E)  E/BB'

Question 4

An electron (charge = -1.6 *10-19C) is moving at 3.0 * 105 m/s in the positive x direction. A magnetic field of 0.80 T is in the positive z direction. The magnetic force on the electron is:

Accepted Answer

A)  0 N 
B)  4.5 * 10-14 N in the positive z direction 
C)  4.5 *10-14 N in the negative z direction 
D)  4.5 *10-14 N in the positive y direction 
E)  4.5 * 10-14 N in the negative y direction 
A)  0 N 
B)  4.5 * 10-14 N in the positive z direction 
C)  4.5 *10-14 N in the negative z direction 
D)  4.5 *10-14 N in the positive y direction 
E)  4.5 * 10-14 N in the negative y direction

Question 5

You are facing a loop of wire which carries a clockwise current of 3.0 A and which surrounds an area of 5.8 x 10−2m2. The magnetic dipole moment of the loop is:

Accepted Answer

A)  3.0 A.m2, into the page 
B)  3.0 A.m2, out of the page 
C)  0.17 A.m2, into the page 
D)  0.17 A.m2, out of the page 
E)  0.17 A.m2, left to right 
A)  3.0 A.m2, into the page 
B)  3.0 A.m2, out of the page 
C)  0.17 A.m2, into the page 
D)  0.17 A.m2, out of the page 
E)  0.17 A.m2, left to right

Question 6

A square loop of wire lies in the plane of the page and carries a current I as shown. There is a uniform magnetic field directed towards the top of the page, as indicated. The loop will tend to rotate:

Accepted Answer

A)  about PQ with KL coming out of the page 
B)  about PQ with KL going into the page 
C)  about RS with MK coming out of the page 
D)  about RS with MK going into the page 
E)  about an axis perpendicular to the page 
A)  about PQ with KL coming out of the page 
B)  about PQ with KL going into the page 
C)  about RS with MK coming out of the page 
D)  about RS with MK going into the page 
E)  about an axis perpendicular to the page

Question 7

A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each 15 cm long. A 0.7 T uniform magnetic field is in the plane of the triangle and is perpendicular to the hypotenuse. The resultant magnetic force on the two equal sides has a magnitude of:

Accepted Answer

A)  0 N 
B)  0.21 N 
C)  0.30 N 
D)  0.41 N 
E)  0.51 N 
A)  0 N 
B)  0.21 N 
C)  0.30 N 
D)  0.41 N 
E)  0.51 N

Question 8

A loop of current-carrying wire has a magnetic dipole moment of 5.0 * 10-4 A.m2. If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?

Accepted Answer

A)  -9.5 x 10-5 J 
B)  -1.5 x 10-4 J 
C)  -1.8 x 10-4 J 
D)  +1.5 x 10-4 J 
E)  +9.5 x 10-5 J 
A)  -9.5 x 10-5 J 
B)  -1.5 x 10-4 J 
C)  -1.8 x 10-4 J 
D)  +1.5 x 10-4 J 
E)  +9.5 x 10-5 J

Question 9

At one instant an electron (charge = -1.6 *10-19C) is moving in the xy plane, the components of its velocity being vx = 5.0 * 105 m/s and vy = 3.0 * 105 m/s. A magnetic field of 0.80 T is in the positive x direction. At that instant the magnitude of the magnetic force on the electron is:

Accepted Answer

A)  0 N 
B)  3.8 * 10-14 N 
C)  6.0 * 10-14 N 
D)  6.4 *10-14 N 
E)  1.0 *10-14 
A)  0 N 
B)  3.8 * 10-14 N 
C)  6.0 * 10-14 N 
D)  6.4 *10-14 N 
E)  1.0 *10-14

Question 10

A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each 15 cm long. A 0.7 T uniform magnetic field is parallel to the hypotenuse. The total magnetic force on the two equal sides has a magnitude of:

Accepted Answer

A)  0 N 
B)  0.21 N 
C)  0.30 N 
D)  0.41 N 
E)  0.51 N 
A)  0 N 
B)  0.21 N 
C)  0.30 N 
D)  0.41 N 
E)  0.51 N

Question 11

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:

Accepted Answer

A)  0.5 
B)  1 
C)  2 
D)  4 
E)  8 
A)  0.5 
B)  1 
C)  2 
D)  4 
E)  8

Question 12

A magnetic field exerts a force on a charged particle:

Accepted Answer

A)  always 
B)  never 
C)  if the particle is moving across the field lines 
D)  if the particle is moving along the field lines 
E)  if the particle is at rest 
A)  always 
B)  never 
C)  if the particle is moving across the field lines 
D)  if the particle is moving along the field lines 
E)  if the particle is at rest

Question 13

A conducting strip of width 1.5 mm is in a magnetic field. As a result, there is a potential difference of 4.3 mV across the width of the strip. What is the magnitude of the electric field in the strip?

Accepted Answer

A)  0.35 V/m 
B)  1.2 V/m 
C)  1.9 V/m 
D)  2.9 V/m 
E)  6.4 V/m 
A)  0.35 V/m 
B)  1.2 V/m 
C)  1.9 V/m 
D)  2.9 V/m 
E)  6.4 V/m

Question 14

An electron is launched with velocity in a uniform magnetic field . The angle $\theta$between and is between 0 and 90o. As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:

Accepted Answer

A)  2πm/eB 
B)  2πmv/eB 
C)  2πmv sin$\theta$/eB 
D)  2πmv cos$\theta$/eB 
E)  none of these 
A)  2πm/eB 
B)  2πmv/eB 
C)  2πmv sin$\theta$/eB 
D)  2πmv cos$\theta$/eB 
E)  none of these

Question 15

The Hall effect can be used to calculate the charge-carrier number density in a conductor. If a conductor carrying a current of 2.0 A is 0.5 mm thick, and the Hall effect voltage is 4.5 µV when it is in a uniform magnetic field of 1.2 T, what is the density of charge carriers in the conductor?

Accepted Answer

A)  1.0 x 1028/m3  
B)  6.7 x 1027/m3 
C)  4.6 x 1027/m3 
D)  1.7 x 1027/m3 
E)  1.2 x 1027/m3 
A)  1.0 x 1028/m3  
B)  6.7 x 1027/m3 
C)  4.6 x 1027/m3 
D)  1.7 x 1027/m3 
E)  1.2 x 1027/m3

Exam 28: Magnetic Fields

The current is from left to right in the conductor shown. The magnetic field is into the page and point S is at a higher potential than point T. The charge carriers are:

An electron moves in the negative x direction, through a uniform magnetic field that is in the negative y direction. The magnetic force on the electron is:

In a certain mass spectrograph, an ion beam passes through a velocity filter consisting of mutually perpendicular fields and . The beam then enters a region of another magnetic field perpendicular to the beam. The radius of curvature of the resulting ion beam is proportional to:

An electron (charge = -1.6 *10-19C) is moving at 3.0 * 105 m/s in the positive x direction. A magnetic field of 0.80 T is in the positive z direction. The magnetic force on the electron is:

You are facing a loop of wire which carries a clockwise current of 3.0 A and which surrounds an area of 5.8 x 10−2m2. The magnetic dipole moment of the loop is:

A square loop of wire lies in the plane of the page and carries a current I as shown. There is a uniform magnetic field directed towards the top of the page, as indicated. The loop will tend to rotate:

A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each 15 cm long. A 0.7 T uniform magnetic field is in the plane of the triangle and is perpendicular to the hypotenuse. The resultant magnetic force on the two equal sides has a magnitude of:

A loop of current-carrying wire has a magnetic dipole moment of 5.0 * 10-4 A.m2. If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?

At one instant an electron (charge = -1.6 *10-19C) is moving in the xy plane, the components of its velocity being vx = 5.0 * 105 m/s and vy = 3.0 * 105 m/s. A magnetic field of 0.80 T is in the positive x direction. At that instant the magnitude of the magnetic force on the electron is:

A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each 15 cm long. A 0.7 T uniform magnetic field is parallel to the hypotenuse. The total magnetic force on the two equal sides has a magnitude of:

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 magnetic field exerts a force on a charged particle:

A conducting strip of width 1.5 mm is in a magnetic field. As a result, there is a potential difference of 4.3 mV across the width of the strip. What is the magnitude of the electric field in the strip?

An electron is launched with velocity in a uniform magnetic field . The angle θ\thetaθ between and is between 0 and 90o. As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:

The Hall effect can be used to calculate the charge-carrier number density in a conductor. If a conductor carrying a current of 2.0 A is 0.5 mm thick, and the Hall effect voltage is 4.5 µV when it is in a uniform magnetic field of 1.2 T, what is the density of charge carriers in the conductor?

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An electron (charge = -1.6 10^-19C) is moving at 3.0 10⁵ m/s in the positive x direction. A magnetic field of 0.80 T is in the positive z direction. The magnetic force on the electron is:

You are facing a loop of wire which carries a clockwise current of 3.0 A and which surrounds an area of 5.8 x 10⁻²m². The magnetic dipole moment of the loop is:

A loop of current-carrying wire has a magnetic dipole moment of 5.0 * 10^-4 A.m². If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?

At one instant an electron (charge = -1.6 10^-19C) is moving in the xy plane, the components of its velocity being v_x = 5.0 10⁵ m/s and v_y = 3.0 * 10⁵ m/s. A magnetic field of 0.80 T is in the positive x direction. At that instant the magnitude of the magnetic force on the electron is:

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, v_proton/v_alpha is:

An electron is launched with velocity in a uniform magnetic field . The angle $\theta$ between and is between 0 and 90^o. As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of: