Question 1

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 2

The figure shows a uniform magnetic field directed to the left and a wire carrying a current into the page.The magnetic force acting on the wire is:

Accepted Answer

A) toward the top of the page 
B) toward the bottom of the page 
C) toward the left 
D) toward the right 
E) zero 
A) toward the top of the page 
B) toward the bottom of the page 
C) toward the left 
D) toward the right 
E) zero

Question 3

The direction of the magnetic field in a certain region of space is determined by firing a test charge into the region with its velocity in various directions in different trials.The field direction is:

Accepted Answer

A) one of the directions of the velocity when the magnetic force is zero 
B) the direction of the velocity when the magnetic force is a maximum 
C) the direction of the magnetic force 
D) perpendicular to the velocity when the magnetic force is zero 
E) none of the above 
A) one of the directions of the velocity when the magnetic force is zero 
B) the direction of the velocity when the magnetic force is a maximum 
C) the direction of the magnetic force 
D) perpendicular to the velocity when the magnetic force is zero 
E) none of the above

Question 4

A coil of 1000 turns of wire has a radius of 12 cm and carries a counterclockwise current of 15A.If it is lying flat on the ground, and the Earth's magnetic field points due north, has a magnitude of 5.8 x 10-5 T, and makes a downward angle of 25° with the vertical, what is the torque on the loop?

Accepted Answer

A) 1.7 x 10-2 N·m west 
B) 3.6 x 10-2 N·m west 
C) 1.7 x 10-2 N·m east 
D) 3.6 x 10-2 N·m east 
E) 3.6 x 10-2 N·m south 
A) 1.7 x 10-2 N·m west 
B) 3.6 x 10-2 N·m west 
C) 1.7 x 10-2 N·m east 
D) 3.6 x 10-2 N·m east 
E) 3.6 x 10-2 N·m south

Question 5

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 6

The diagrams show five possible orientations of a magnetic dipole in a uniform magnetic field .For which of these does the magnetic torque on the dipole have the greatest magnitude?

Accepted Answer

A) I 
B) II 
C) III 
D) IV 
E) V 
A) I 
B) II 
C) III 
D) IV 
E) V

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 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 8

A hydrogen atom that has lost its electron is moving east in a region where the magnetic field is directed from south to north.It will be deflected:

Accepted Answer

A) up 
B) down 
C) north 
D) south 
E) not at all 
A) up 
B) down 
C) north 
D) south 
E) not at all

Question 9

A beam of electrons is sent horizontally down the axis of a tube to strike a fluorescent screen at the end of the tube.On the way, the electrons encounter a magnetic field directed vertically downward.The spot on the screen will therefore be deflected:

Accepted Answer

A) upward 
B) downward 
C) to the right as seen from the electron source 
D) to the left as seen from the electron source 
E) not at all 
A) upward 
B) downward 
C) to the right as seen from the electron source 
D) to the left as seen from the electron source 
E) not at all

Question 10

A strip 1.2 mm wide is moving at a speed of 25 cm/s through a uniform magnetic field of 5.6 T.What is the maximum Hall voltage across the strip?

Accepted Answer

A) 1.7 mV 
B) 8.5 mV 
C) 27 mV 
D) 1.2 V 
E) 17 V 
A) 1.7 mV 
B) 8.5 mV 
C) 27 mV 
D) 1.2 V 
E) 17 V

Question 11

A loop of current-carrying wire has a magnetic dipole moment of 5.0 * 10-4 A.m2.The moment initially is aligned with a 0.50-T magnetic field.To rotate the loop so its dipole moment is perpendicular to the field and hold it in that orientation, you must do work of:

Accepted Answer

A) 0 J 
B) 2.5*10-4 J 
C) -2.5 *10-4 J 
D) 1.0 * 10-3 J 
E) -1.0 * 10-3 J 
A) 0 J 
B) 2.5*10-4 J 
C) -2.5 *10-4 J 
D) 1.0 * 10-3 J 
E) -1.0 * 10-3 J

Exam 28: Magnetic Fields

A magnetic field exerts a force on a charged particle:

The figure shows a uniform magnetic field directed to the left and a wire carrying a current into the page.The magnetic force acting on the wire is:

The direction of the magnetic field in a certain region of space is determined by firing a test charge into the region with its velocity in various directions in different trials.The field direction is:

A coil of 1000 turns of wire has a radius of 12 cm and carries a counterclockwise current of 15A.If it is lying flat on the ground, and the Earth's magnetic field points due north, has a magnitude of 5.8 x 10-5 T, and makes a downward angle of 25° with the vertical, what is the torque on the loop?

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?

The diagrams show five possible orientations of a magnetic dipole in a uniform magnetic field .For which of these does the magnetic torque on the dipole have the greatest magnitude?

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 hydrogen atom that has lost its electron is moving east in a region where the magnetic field is directed from south to north.It will be deflected:

A beam of electrons is sent horizontally down the axis of a tube to strike a fluorescent screen at the end of the tube.On the way, the electrons encounter a magnetic field directed vertically downward.The spot on the screen will therefore be deflected:

A strip 1.2 mm wide is moving at a speed of 25 cm/s through a uniform magnetic field of 5.6 T.What is the maximum Hall voltage across the strip?

A loop of current-carrying wire has a magnetic dipole moment of 5.0 * 10-4 A.m2.The moment initially is aligned with a 0.50-T magnetic field.To rotate the loop so its dipole moment is perpendicular to the field and hold it in that orientation, you must do work of:

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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?

A loop of current-carrying wire has a magnetic dipole moment of 5.0 * 10^-4 A.m².The moment initially is aligned with a 0.50-T magnetic field.To rotate the loop so its dipole moment is perpendicular to the field and hold it in that orientation, you must do work of: