Question 1

What is the radius of curvature of the path of a 3.0-keV proton in a perpendicular magnetic field of magnitude 0.80 T?

Accepted Answer

A)  9.9 mm
B)  1.1 cm
C)  1.3 cm
D)  1.4 cm
E)  7.6 mmF) B) and C)
G) A) and C)

Question 2

An electron moving in the positive x direction experiences a magnetic force in the positive z direction. If Bx = 0, what is the direction of the magnetic field?

Accepted Answer

A)  negative y direction
B)  positive y direction
C)  negative z direction
D)  positive z direction
E)  negative x directionF) A) and D)
G) D) and E)

Question 3

An explorer walks into a lab in a science building. She has a compass in her hand and finds that the south pole of her compass points toward the room's east wall when she is nearer that wall and toward the west wall when she is nearer that wall. You could explain this if magnetized metal had been installed in the east and west walls with north poles pointing into the room. If no magnetic material was installed in the north or south walls of the room, she would expect that

Accepted Answer

A)  the south pole of the compass would tend to point toward those walls.
B)  the north pole of the compass would tend to point toward those walls.
C)  the compass needle would not point in any particular direction.
D)  the north pole of the compass needle would tend to point toward the centers of those walls, but the south pole would tend to point toward the sides of those walls.
E)  the south pole of the compass needle would tend to point toward the centers of those walls, but the north pole would tend to point toward the sides of those walls.F) C) and E)
G) B) and D)

Question 4

A current of 4.0 A is maintained in a single circular loop having a circumference of 80 cm. An external magnetic field of 2.0 T is directed so that the angle between the field and the plane of the loop is 20°. Determine the magnitude of the torque exerted on the loop by the magnetic forces acting upon it.

Accepted Answer

A)  0.41 N ⋅ m
B)  0.14 N ⋅ m
C)  0.38 N ⋅ m
D)  0.27 N ⋅ m
E)  0.77 N ⋅ mF) B) and C)
G) C) and D)

Question 5

One reason why we know that magnetic fields are not the same as electric fields is because the force exerted on a charge +q

Accepted Answer

A)  is in opposite directions in electric and magnetic fields.
B)  is in the same direction in electric and magnetic fields.
C)  is parallel to a magnetic field and perpendicular to an electric field.
D)  is parallel to an electric field and perpendicular to a magnetic field.
E)  is zero in both if the charge is not moving.F) C) and D)
G) A) and D)

Question 6

A straight wire carries a current of 40 A in a uniform magnetic field (magnitude = 80 mT) . If the force per unit length on this wire is 2.0 N/m, determine the angle between the wire and the magnetic field.

Accepted Answer

A)  either 39° or 141°
B)  either 25° or 155°
C)  either 70° or 110°
D)  either 42° or 138°
E)  either 65° or 115°F) B) and D)
G) A) and E)

Question 7

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Accepted Answer

A)  D.
B)  E.
C)  F.
D)  G.
E)  H.F) A) and C)
G) A) and B)

Question 8

A rectangular coil (0.20 m × 0.80 m)  has 200 turns and is in a uniform magnetic field of 0.30 T. When the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.080 N ⋅ m. What is the current in the coil?

Accepted Answer

A)  5.0 mA
B)  1.7 A
C)  8.3 mA
D)  1.0 A
E)  42 mAF) None of the above
G) B) and C)

Question 9

A straight 10-cm wire bent at its midpoint so as to form an angle of 90° carries a current of 10 A. It lies in the xy plane in a region where the magnetic field is in the positive z direction and has a constant magnitude of 3.0 mT. What is the magnitude of the magnetic force on this wire?

Accepted Answer

A)  3.2 mN
B)  2.1 mN
C)  5.3 mN
D)  4.2 mN
E)  6.0 mNF) A) and B)
G) B) and C)

Question 10

A charged particle (mass = m, charge = q > 0)  moves in a region of space where the magnetic field has a constant magnitude of B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with speed v?

Accepted Answer

A)  qvB toward the east
B)  Zero
C)  qvB toward the west
D)  qvB upward
E)  qvB toward the southF) C) and E)
G) B) and C)

Question 11

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Accepted Answer

A)  E.
B)  F.
C)  G.
D)  H.
E)  A.F) A) and C)
G) A) and D)

Question 12

A proton is accelerated from rest through a potential difference of 150 V. It then enters a region of uniform magnetic field and moves in a circular path (radius = 12 cm) . What is the magnitude of the magnetic field in this region?

Accepted Answer

A)  18 mT
B)  12 mT
C)  15 mT
D)  22 mT
E)  10 mTF) All of the above
G) B) and C)

Question 13

You stand near the Earth's equator. A positively charged particle that starts moving parallel to the surface of the Earth in a straight line directed east is initially deflected upwards. If you know there are no electric fields in the vicinity, a possible reason why the particle does not initially acquire a downward component of velocity is because near the equator the magnetic field lines of the Earth are directed

Accepted Answer

A)  upward.
B)  downward.
C)  from south to north.
D)  from north to south.
E)  from east to west.F) C) and D)
G) B) and E)

Question 14

A proton is accelerated from rest through a potential difference of 2.5 kV and then moves perpendicularly through a uniform 0.60-T magnetic field. What is the radius of the resulting path?

Accepted Answer

A)  15 mm
B)  12 mm
C)  18 mm
D)  24 mm
E)  8.5 mmF) A) and B)
G) None of the above

Question 15

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H.  When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Accepted Answer

A)  A.
B)  B.
C)  C.
D)  D.
E)  E.F) A) and D)
G) None of the above

Question 16

On the average, in a ferromagnetic domain permanent atomic magnetic moments are aligned ____ to one another.

Accepted Answer

A)  antiparallel
B)  parallel
C)  perpendicular
D)  alternately parallel and antiparallel
E)  randomly relativeF) B) and D)
G) B) and C)

Question 17

A straight wire is bent into the shape shown. Determine the net magnetic force on the wire when the current I travels in the direction shown in the magnetic field  . ​  ​

Accepted Answer

A)  2IBL in the −z direction
B)  2IBL in the +z direction
C)  4IBL in the +z direction
D)  4IBL in the −z direction
E)  zeroF) B) and E)
G) A) and E)

Question 18

A proton with a kinetic energy of 0.20 keV follows a circular path in a region where the magnetic field is uniform and has a magnitude of 60 mT. What is the radius of this path?

Accepted Answer

A)  4.1 cm
B)  2.9 cm
C)  3.4 cm
D)  5.1 cm
E)  2.4 cmF) A) and B)
G) None of the above

Question 19

An unusual lightning strike has a vertical portion with a positive current of +400 A upwards. The Earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 μT. In N, the force exerted by the Earth's magnetic field on the 25-m-long current is

Accepted Answer

A)  0.
B)  0.012 N, East.
C)  0.012 N, West.
D)  0.30 N, West.
E)  300 N, East.F) C) and E)
G) B) and D)

Question 20

When a ferromagnetic material that has been magnetized is brought to a temperature greater than the Curie temperature, what happens to its residual magnetism?

Accepted Answer

A)  Nothing happens to the residual magnetism.
B)  The residual magnetism disappears.
C)  The residual magnetism reaches it's highest value.
D)  All the magnetic domains causing magnetism become a single domain.
E)  The material of the magnet melts causing currents that are magnetic.F) A) and E)
G) C) and D)

Exam 30: Magnetic Fields and Forces

One reason why we know that magnetic fields are not the same as electric fields is because the force exerted on a charge +q

Correct Answer
verified

A proton with a kinetic energy of 0.20 keV follows a circular path in a region where the magnetic field is uniform and has a magnitude of 60 mT. What is the radius of this path?

Correct Answer
verified

A charged particle (mass = m, charge = q > 0) moves in a region of space where the magnetic field has a constant magnitude of B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with speed v?

Correct Answer
verified

A straight 10-cm wire bent at its midpoint so as to form an angle of 90° carries a current of 10 A. It lies in the xy plane in a region where the magnetic field is in the positive z direction and has a constant magnitude of 3.0 mT. What is the magnitude of the magnetic force on this wire?

Correct Answer
verified

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Correct Answer
verified

When a ferromagnetic material that has been magnetized is brought to a temperature greater than the Curie temperature, what happens to its residual magnetism?

Correct Answer
verified

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Correct Answer
verified

An electron moving in the positive x direction experiences a magnetic force in the positive z direction. If Bx = 0, what is the direction of the magnetic field?

Correct Answer
verified

A straight wire carries a current of 40 A in a uniform magnetic field (magnitude = 80 mT) . If the force per unit length on this wire is 2.0 N/m, determine the angle between the wire and the magnetic field.

Correct Answer
verified

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Correct Answer
verified

A straight wire is bent into the shape shown. Determine the net magnetic force on the wire when the current I travels in the direction shown in the magnetic field .

Correct Answer
verified

On the average, in a ferromagnetic domain permanent atomic magnetic moments are aligned ____ to one another.

Correct Answer
verified

A rectangular coil (0.20 m × 0.80 m) has 200 turns and is in a uniform magnetic field of 0.30 T. When the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.080 N ⋅ m. What is the current in the coil?

Correct Answer
verified

Correct Answer
verified

A proton is accelerated from rest through a potential difference of 150 V. It then enters a region of uniform magnetic field and moves in a circular path (radius = 12 cm) . What is the magnitude of the magnetic field in this region?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

A proton is accelerated from rest through a potential difference of 2.5 kV and then moves perpendicularly through a uniform 0.60-T magnetic field. What is the radius of the resulting path?

Correct Answer
verified

What is the radius of curvature of the path of a 3.0-keV proton in a perpendicular magnetic field of magnitude 0.80 T?

Correct Answer
verified

An unusual lightning strike has a vertical portion with a positive current of +400 A upwards. The Earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 μT. In N, the force exerted by the Earth's magnetic field on the 25-m-long current is

Correct Answer
verified

Exam 30: Magnetic Fields and Forces

One reason why we know that magnetic fields are not the same as electric fields is because the force exerted on a charge +q

Correct AnswerverifiedShow Answer

A proton with a kinetic energy of 0.20 keV follows a circular path in a region where the magnetic field is uniform and has a magnitude of 60 mT. What is the radius of this path?

Correct AnswerverifiedShow Answer

A charged particle (mass = m, charge = q > 0) moves in a region of space where the magnetic field has a constant magnitude of B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with speed v?

Correct AnswerverifiedShow Answer

A straight 10-cm wire bent at its midpoint so as to form an angle of 90° carries a current of 10 A. It lies in the xy plane in a region where the magnetic field is in the positive z direction and has a constant magnitude of 3.0 mT. What is the magnitude of the magnetic force on this wire?

Correct AnswerverifiedShow Answer

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Correct AnswerverifiedShow Answer

When a ferromagnetic material that has been magnetized is brought to a temperature greater than the Curie temperature, what happens to its residual magnetism?

Correct AnswerverifiedShow Answer

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Correct AnswerverifiedShow Answer

An electron moving in the positive x direction experiences a magnetic force in the positive z direction. If Bx = 0, what is the direction of the magnetic field?

Correct AnswerverifiedShow Answer

A straight wire carries a current of 40 A in a uniform magnetic field (magnitude = 80 mT) . If the force per unit length on this wire is 2.0 N/m, determine the angle between the wire and the magnetic field.

Correct AnswerverifiedShow Answer

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

Correct AnswerverifiedShow Answer

A straight wire is bent into the shape shown. Determine the net magnetic force on the wire when the current I travels in the direction shown in the magnetic field . ​ ​

Correct AnswerverifiedShow Answer

On the average, in a ferromagnetic domain permanent atomic magnetic moments are aligned ____ to one another.

Correct AnswerverifiedShow Answer

A rectangular coil (0.20 m × 0.80 m) has 200 turns and is in a uniform magnetic field of 0.30 T. When the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.080 N ⋅ m. What is the current in the coil?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

A proton is accelerated from rest through a potential difference of 150 V. It then enters a region of uniform magnetic field and moves in a circular path (radius = 12 cm) . What is the magnitude of the magnetic field in this region?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

A proton is accelerated from rest through a potential difference of 2.5 kV and then moves perpendicularly through a uniform 0.60-T magnetic field. What is the radius of the resulting path?

Correct AnswerverifiedShow Answer

What is the radius of curvature of the path of a 3.0-keV proton in a perpendicular magnetic field of magnitude 0.80 T?

Correct AnswerverifiedShow Answer

An unusual lightning strike has a vertical portion with a positive current of +400 A upwards. The Earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 μT. In N, the force exerted by the Earth's magnetic field on the 25-m-long current is

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
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Correct Answer
verified

Correct Answer
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Correct Answer
verified

Correct Answer
verified

A straight wire is bent into the shape shown. Determine the net magnetic force on the wire when the current I travels in the direction shown in the magnetic field .

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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