Deck 19: Magnetism

Question 1

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

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

Answer 1

a magnetic south pole

Question 2

Electrical charges and magnetic poles have many similarities,but one difference is:

A)opposite magnetic poles repel.
B)one magnetic pole cannot create magnetic poles in other materials.
C)a magnetic pole cannot be isolated.
D)magnetic poles do not produce magnetic fields.

Answer 2

a magnetic pole cannot be isolated.

Question 3

A bar magnet is attached solidly to a frictionless surface and its length is aligned with the x axis.To the right of the first magnet a short distance away is a second bar magnet with its center placed on the x axis and its length perpendicular to the x axis.The second magnet is free to move.Once placed in position at rest,which best describes the initial motion of the second magnet?

A)The magnet will move away from the fixed magnet.
B)The magnet will not move.
C)The magnet will move toward the fixed magnet.
D)The magnet will start to rotate.

Answer 3

The magnet will start to rotate.

Question 4

A proton moves across the Earth's equator in a northeasterly direction.At this point the Earth's magnetic field has a direction due north and is parallel to the surface.What is the direction of the force acting on the proton at this instant?

A)toward the northwest
B)out of the Earth's surface
C)into the Earth's surface
D)toward the northeast

Question 5

The right-hand rule allows one to find a property of the interaction of a magnetic field with a charged particle.The right-hand rule applied to moving charges:

A)results in positive charges moving clockwise.
B)results in negative charges moving clockwise.
C)can be used for positive charges only.
D)gives the direction of the force on a charge moving in a magnetic field.

Question 6

If a proton is released at the equator and falls toward the Earth under the influence of gravity,the magnetic force on the proton will be toward the:

A)north.
B)south.
C)east.
D)west.

Question 7

The magnetic field of the Earth is believed responsible for which of the following?

A)deflection of both charged and uncharged cosmic rays
B)deflection of charged cosmic rays
C)ozone in the upper atmosphere
D)solar flares

Question 8

Three identical bar magnets,each 2 cm long,are placed in a straight line on a frictionless surface with their ends equally spaced with 2 cm between ends.They are constrained so they cannot rotate,but they can slide along the straight line.The left magnet has its north pole nearest the north pole of the middle magnet,and the right magnet has its south pole toward the middle magnet's south pole.Once they are in place and released from rest,which of the following best describes the motion of the magnets?

A)The end magnets will move away from the center magnet.
B)The magnets will not move since they are equally spaced.
C)The magnets will snap together.
D)None of the above would happen.

Question 9

The term magnetic declination refers to which of the following?

A)angle between Earth's magnetic field and Earth's surface
B)Earth's magnetic field strength at the equator
C)tendency for Earth's field to reverse itself
D)angle between directions to true north and magnetic north

Question 10

Which of the following is not a hard magnetic material?

A)iron
B)cobalt
C)nickel
D)both b and c

Question 11

The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the particle velocity and field?

A)zero
B)180°
C)90°
D)45°

Question 12

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:

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

Question 13

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

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

Question 14

A soft magnetic material has which property?

A)It cannot be magnetized.
B)It is easy to magnetize.
C)It is hard to magnetize.
D)It attracts slowly moving charges.

Question 15

There is a magnetic force on a particle.It is possible that the particle is:

A)uncharged.
B)stationary.
C)moving in the direction of the magnetic field.
D)not part of a wire.

Question 16

The dip angle is:

A)another term for magnetic declination.
B)a measure of the tendency for a compass to point south.
C)close to or at zero near the equator.
D)close to or at zero just north of Hudson Bay.

Question 17

Which of the following locations has the smallest (in magnitude)magnetic declination?

A)Washington state
B)the South Carolina - Georgia border
C)the San Francisco - Oakland area
D)western Colorado

Question 18

An electron which moves with a speed of 4.5 × 10⁴ m/s perpendicular to a uniform magnetic field of 0.57 T experiences a force of what magnitude? (e = 1.6 × 10−¹⁹ C)

A)zero
B)6.57E-33 N
C)2.05E-15 N
D)1.26E-14 N
E)4.10E-15 N

Question 19

Assume that a uniform magnetic field is directed into this page.If an electron 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 electron?

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

Question 20

Different units can be used to measure the same physical quantity,differing only by some multiplicative factor.The cgs unit for magnetic field,the gauss,is equal to ________ tesla.

A)10⁴
B)10^-4
C)0.5
D)These units do not measure the same physical quantity.

Question 21

A proton is released such that it has an initial speed of 4.1 × 10⁵ m/s from left to right across the page.A magnetic field of 0.8 T is present at an angle of 45° to the horizontal direction (or positive x axis).What is the magnitude of the force experienced by the proton? (q_p = 1.6 × 10−¹⁹ C)

A)5.9E-33 N
B)9.3E-33 N
C)3.7E-14 N
D)4.5E-14 N
E)​3.7E-14 N

Question 22

​An electron is accelerated from rest through 2300 V and then enters a region of uniform magnetic field with magnitude 1.25 T.What is the magnitude of the maximum magnetic force acting on the electron?

A)​5.68E-12 N
B)​4.02E-12 N
C)​4.07E-12 N
D)​2.03E-12 N

Question 23

The path of a charged particle moving parallel to a uniform magnetic field will be a

A)straight line.
B)circle.
C)ellipse.
D)parabola.

Question 24

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

Question 25

A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field.A deuteron has the same charge as the proton but has twice its mass.The ratio of the acceleration of the proton to that of the deuteron is:

A)0.5.
B)1.
C)2.
D)There is no acceleration in this case.

Question 26

A proton moving with a speed of 3.20 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.0786 T will follow which of the paths described below? (q_p = 1.60 × 10−¹⁹ C and m_p = 1.67 × 10−²⁷ kg)

A)a straight-line path
B)a circular path of 4.25 cm radius
C)a circular path of 10.9 cm radius
D)a circular path of 1.52 cm radius
E)a circular path of 54.1 cm radius

Question 27

A proton is released such that its initial velocity is from right to left across this page.The proton's path,however,is deflected in a direction toward the bottom edge of the page due to the presence of a uniform magnetic field.What is the direction of this field?

A)out of the page
B)into the page
C)from bottom edge to top edge of the page
D)from right to left across the page

Question 28

A proton moving at a speed of 4.2 × 10⁶ m/s cuts across the lines of a magnetic field at an angle of 78°.The strength of the field is 0.91 × 10−⁴ T.What is the magnitude of the force acting on the proton? (q_p = 1.6 × 10−¹⁹ C)

A)1.3E-17 N
B)3.1E-17 N
C)6.0E-17 N
D)7.2E-9 N
E)​9.6E-36 N

Question 29

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 3.37 cm while isotope Y moves along a path 3.58 cm in radius.What is the ratio of the two isotope masses,
?

A)0.941
B)1.06
C)0.886
D)1.13
E)Not enough information is given.

Question 30

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 0.86 T.Find the time for the proton to make one complete circular orbit.

A)2.4 × 10−⁸ s
B)7.6 × 10−⁸ s
C)3.8 × 10−⁸ s
D)1.2 × 10−⁸ s
E)Not enough information is given.

Question 31

If a charged particle is moving in a uniform magnetic field,its path can be

A)a straight line.
B)a circle.
C)a helix.
D)any of the above.

Question 32

A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field.A deuteron has the same charge as the proton but has twice its mass.The ratio of the magnetic force on the proton to that on the deuteron is:

A)0.5.
B)1.
C)2.
D)There is no magnetic force in this case.

Question 33

An electron moves through a region of crossed electric and magnetic fields.The electric field E = 2 300 V/m and is directed straight down.The magnetic field B = 0.95 T and is directed to the left.For what velocity v of the electron into the paper will the electric force exactly cancel the magnetic force?

A)2 400 m/s
B)2 200 m/s
C)3 500 m/s
D)4 400 m/s
E)3 800 m/s

Question 34

A proton moves through a magnetic field of magnitude 1.40 T with speed 5.00 *10⁶ m/s.What is the magnitude of the maximum acceleration of the proton? The mass of a proton is 1.67 *10^-27 kg,and its charge is 1.6 *10^-19 C.

A)3.42E+14 m/s
B)6.71E+14 m/s
C)3.35E+21 m/s
D)1.71E+21 m/s

Question 35

A proton,which moves perpendicular to a magnetic field of 1.4 T in a circular path of radius 0.074 m,has what speed? (q_p = 1.60 × 10−¹⁹ C and m_p = 1.67 × 10−²⁷ kg)

A)7.3E+5 m/s
B)2.8E+7 m/s
C)5.1E+6 m/s
D)9.9E+6 m/s
E)3.9E+6 m/s

Question 36

At the Fermilab accelerator in Weston,Illinois,singly-charged ions with momentum 3.3 × 10−¹⁶ kg⋅m/s are held in a circular orbit of radius 1.00 km by an upward magnetic field.What B field must be used to maintain the ions in this orbit? (qion = 1.60 × 10−¹⁹ C)

A)5.3 T
B)2.1 T.
C)2.1 T
D)0.19 T
E)0.48 T

Question 37

​A proton is circling the Earth above the magnetic equator,where Earth's magnetic field is directed horizontally north and has a magnitude of 4.00 × 10^-8 T.If the proton is moving at a speed of 2.7 × 10⁷ m/s,how far above the surface of the Earth is the proton? Earth's radius is 6.38 × 10⁶ m,a proton's mass is 1.67 × 10^-27 kg,and its charge is 1.6 × 10^-19 C.

A)​7.05E+6 m
B)​1.34E+7 m
C)​1.03E+8 m
D)​6.65E+5 m

Question 38

The magnetic field of the Earth at a particular location is directed vertically downward with magnitude of 40.0 μT.An electron is moving horizontally toward the west in this field with a speed of 5.2 × 10⁶ m/s.What are the direction and magnitude of the magnetic force the field exerts on the electron? (e = 1.6 × 10^-19 C)

A)3.33E-17,south
B)3.33E-17,north
C)2.08E-20,south
D)2.08E-20,north

Question 39

A deuteron,with the same charge but twice the mass of a proton,moves with a speed of 6.00 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.0525 T.Which of the paths described below would it follow? (q_p = 1.60 × 10−¹⁹ C and m_d = 3.34 × 10−²⁷ kg)

A)a straight-line path
B)a circular path of 61.1 cm radius
C)a circular path of 23.9 cm radius
D)a circular path of 2.14 cm radius
E)a circular path of 1.70 cm radius

Question 40

In a mass spectrometer,an ion will have a smaller radius for its circular path if

A)its speed is greater.
B)its mass is greater.
C)its charge is greater.
D)the magnetic field is weaker.

Question 41

A horizontal wire of length 3.0 m carries a current of 6.0 A and is oriented so that the current direction is 50° S of W.The Earth's magnetic field is due north at this point and has a strength of 0.14 × 10−⁴ T.What is the direction of the force on the wire?

A)out of the Earth's surface
B)toward the Earth's surface
C)due east
D)40° S of E

Question 42

A proton and an alpha particle are moving perpendicular to a uniform magnetic field with the same speed.If the velocity of the proton is at an angle of 20° with respect to the magnetic field direction,at what angle to the magnetic field direction would the alpha particle be moving if it experiences the same magnitude acceleration as the proton? The alpha particle has 4 times the mass of the proton and twice its charge.

A)43°
B)10°
C)62°
D)9.8°

Question 43

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 force acting on the loop is

A)2ILB.
B)ILB.
C)IBL².
D)zero.

Question 44

If an electron is released at the equator and falls toward the Earth under the influence of gravity,the magnetic force on the electron will be toward the:

A)south.
B)east.
C)west.
D)north.

Question 45

A horizontal wire of length 4.5 m carries a current of 5.8 A and is oriented so that the current direction is 53° S of W.The Earth's magnetic field is due north at this point and has a strength of 0.14 × 10−⁴ T.What is the size of the force on the wire?

A)2.9E-4 N
B)3.4E-4 N
C)1.4E-4 N
D)2.2E-4 N
E)7.8E-5 N

Question 46

A wire in a uniform magnetic field of 0.350 T carries a current of 3.50 A.If the magnitude of the magnetic force per unit length on the wire is 0.278 N/m,what is the angle between the magnetic field and the current?

A)13.1°
B)19.9°
C)4.56°
D)52.6°

Question 47

A charged particle moving perpendicular to a magnetic field has a magnet force on it.But when an observer moves with the particle,so that the particle has a relative velocity of zero with respect to the observer,one would expect there would be no magnetic force.Yet there is still a force.If it is not a magnetic force,then what is the source of this force?

A)It is an electrical force.
B)It is due to the ether.
C)It is a gravitational force.
D)It is something other than any of the above.

Question 48

A copper wire of length 25.0 cm is in a magnetic field of 0.36 T.If it has a mass of 11.0 g,what is the minimum current through the wire that would cause a magnetic force equal to its weight?

A)12 A
B)0.48 A
C)1.2 A
D)3.3 A
E)0.75 A

Question 49

The force exerted on a current-carrying wire located in an external magnetic field is directly proportional to which of the following?

A)current strength
B)field strength
C)both A and B
D)None of the above are valid.

Question 50

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

A)50.0°.
B)12.5°.
C)57.7°.
D)12.2°.

Question 51

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?

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

Question 52

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)57.7°.
B)12.5°.
C)12.2°.
D)50.0°.

Question 53

Which statement regarding the force of a magnetic field on a current-carrying wire is true?​

A)​The magnetic force on the wire is independent of the direction of the current.
B)​The force on the wire is directed parallel to both the wire and the magnetic field.
C)​The force takes its largest value when the magnetic field is parallel to the wire.
D)​All of the above statements are false.

Question 54

A wire is lying horizontally in the north-south direction and the horizontal magnetic field is toward the east.Some positive charges in the wire move north and an equal number of negative charges move south.The direction of the force on the wire will be:

A)east.
B)down,into the page.
C)up,out of the page.
D)There is no magnetic force.

Question 55

The direction of the force on a current carrying wire located in an external magnetic field is which of the following?

A)perpendicular to the current
B)perpendicular to the field
C)Both choices A and B are valid.
D)None of the above are valid.

Question 56

An electron is moving at a speed of 4.8 × 10⁶ m/s at an angle of 30.0° with respect to a uniform magnetic field of 9.2 × 10^-4 T.What is the radius of the resulting helical path? (m_e = 9.11 × 10^-31 kg,q_e = 1.60 × 10^-19 C)

A)2.6 cm
B)3.8 cm
C)5.5 cm
D)1.5 cm
E)2.9 cm

Question 57

A 1.0-m wire segment carrying a current of 0.55 A oriented parallel to a uniform magnetic field of 0.80 T experiences a force of what magnitude?

A)0.44 N
B)0.22 N
C)0.70 N
D)0.35 N
E)0.00 N

Question 58

A current-carrying wire of length 52.0 cm is positioned perpendicular to a uniform magnetic field.If the current is 15.0 A and it is determined that there is a resultant force of 2.3 N on the wire due to the interaction of the current and field,what is the magnetic field strength?

A)0.29 T
B)0.029 T
C)0.020 T
D)0.38 T
E)0.18 T

Question 59

A proton with initial kinetic energy KE is moving in circular motion in a uniform magnetic field.When it has completed one eighth of a revolution,what is its kinetic energy?

A)1.4KE
B)0.71KE
C)KE
D)The value is not given.

Question 60

A proton and an alpha particle are moving perpendicular to a uniform magnetic field with the same speeds.If the velocity of the proton is at an angle of 20° with respect to the magnetic field direction,at what angle to the magnetic field direction would the alpha particle be moving if it experiences the same magnitude magnetic force as the proton? The alpha particle has 4 times the mass of the proton and twice its charge.

A)10°
B)62°
C)43°
D)9.8°

Question 61

A 198-m-long wire carrying a current of 3.5 A will be accompanied by a magnetic field of what strength at a distance of 0.054 m from the wire? (magnetic permeability in empty space µ₀ = 4π × 10−⁷ T⋅m/A)

A)4.1E-5 T
B)8.3E-6 T
C)1.3E-5 T
D)6.5E-6 T
E)zero

Question 62

An incredible amount of electrical energy passes down the funnel of a large tornado every second.Measurements at a distance of 12.8 km from a large tornado showed an almost constant magnetic field of 2.35 × 10−⁸ T associated with the tornado.What was the average current going down the funnel? (µ₀ = 4π × 10−⁷ T⋅m/A)

A)3.0E+3 A
B)1.5E+3 A
C)7.5E+2 A
D)9.6E+2 A
E)4.7E+3 A

Question 63

A superconducting wire carries a current of 7.0 kA.Find the magnetic field at a distance of 1.5 m from the wire.(µ₀ = 4π × 10−⁷ T⋅m/A)

A)9.3E-4 T
B)3.0E-4 T
C)2.9E-3 T
D)1.5E-3 T
E)5.9E-3 T

Question 64

Two long parallel wires 10.0 cm apart carry currents of 3.0 A and 2.9 A in the same direction.Is there any point between the two wires where the magnetic field is zero?

A)yes,midway between the wires
B)yes,4.9 cm from the 3.0-A wire
C)yes,5.1 cm from the 3.0-A wire
D)yes,5.1 cm from the 2.9-A wire
E)no.

Question 65

The current in a long wire creates a magnetic field in the region around the wire.How is the strength of the field at distance r from the wire center related to the magnitude of the field?

A)field directly proportional to r
B)field inversely proportional to r
C)field directly proportional to r²
D)field inversely proportional to r²

Question 66

A high-voltage power line 23.0 m above the ground carries a current of 2 200 A.What is the magnetic field due to the current directly underneath the power line? (µ₀ = 4π × 10−⁷ T⋅m/A)

A)19.1 µT
B)60.1 µT
C)60.9 mT
D)12.0 mT
E)12.0 T

Question 67

Niobium metal becomes a superconductor (with electrical resistance equal to zero)when cooled below 9.00 K.If superconductivity is destroyed when the surface magnetic field exceeds 0.100 T,determine the maximum current a 5.31-mm-diameter niobium wire can carry and remain superconducting.(µ₀ = 4π × 10−⁷ T⋅m/A)

A)2660 A
B)423 A
C)211 A
D)1330 A
E)4170 A

Question 68

A circular current loop is placed in an external magnetic field.How is the torque related to the radius of the loop?

A)directly proportional to radius
B)inversely proportional to radius
C)directly proportional to radius squared
D)inversely proportional to radius squared

Question 69

Two long parallel wires 45.6 cm apart are carrying currents of 13.0 A and 23.0 A in the same direction.What is the magnitude of the magnetic field halfway between the wires?

A)8.77E-6 T
B)3.16E-5 T
C)1.14E-5 T
D)2.02E-5 T
E)4.39E-6 T

Question 70

A 10.0-m-long copper wire with cross-sectional area 1.25 × 10^-4 m² is bent into a square loop,and then connected to a 0.25-V battery.The loop is then placed in a uniform magnetic field of magnitude 0.19 T.What is the maximum torque that can act on this loop? The resistivity of copper is 1.70 × 10^-8 Ω·m.

A)2.2E+2 N·m
B)1.8E+2 N·m
C)9.7E+2 N·m
D)5.6E+2 N·m

Question 71

A circular loop carrying a current of 1.25 A is oriented in a magnetic field of 0.22 T.The loop has an area of 0.10 m² and is mounted on an axis,perpendicular to the magnetic field,which allows the loop to rotate.If the plane of the loop is oriented parallel to the field,what torque is created by the interaction of the loop current and the field?

A)0.018 N⋅m
B)2.8 N⋅m
C)0.028 N⋅m
D)0.014 N⋅m
E)57 N⋅m

Question 72

A current in a long,straight wire produces a magnetic field.The magnetic field lines:

A)go out from the wire to infinity.
B)come in from infinity to the wire.
C)form circles that pass through the wire.
D)form circles that go around the wire.

Question 73

A square coil and a triangular coil each have sides of length L.The triangular coil has twice as many turns as the square coil.If a the same current is sent through each coil,when the coils are placed in the same uniform magnetic field making an angle of 30^° with the planes of the coils,which coil experiences the greater torque?

A)the square coil
B)the triangular coil
C)Both coils experience the same torque.
D)It depends on the magnitude of the magnetic field that the coils are placed in.

Question 74

Square coil A has 2N turns and sides of length L,and square coil B has N turns and sides of length 2L.When a current of 2 amps is sent through coil A and a current of 1 amp is sent through coil B,which coil has the greater magnetic moment?

A)coil A
B)coil B
C)Both have the same magnetic moment.
D)More information is needed.

Question 75

A square loop of wire has a current going around it.The magnetic field from the current on each side of the loop results in a magnetic force on the wire on the opposite side.Each resulting magnetic force on the opposite side wire

A)pushes inward on the loop.
B)is actually zero since a current cannot push on itself.
C)depends on whether the current is clockwise of counterclockwise.
D)pushes outward on the loop.

Question 76

Magnetism had been a known phenomenon for some time before its relation to electric currents was found.That a current in a wire produces a magnetic field was discovered by:

A)Maxwell.
B)Ampere.
C)Oersted.
D)Tesla.

Question 77

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

A)2ILB.
B)ILB.
C)IBL².
D)zero.

Question 78

A circular coil (radius = 0.25 m)has 143 turns and is in a uniform magnetic field.If the orientation of the coil is varied through all possible positions,the maximum torque on the coil by magnetic forces is 0.29 N⋅m when the current in the coil is 2.7 mA.What is the magnitude of the magnetic field?

A)5.47 T
B)0.304 T
C)3.83 T
D)137 T

Question 79

A circular loop carrying a current of 1.6 A is oriented in a magnetic field of 0.30 T.The loop has an area of 0.14 m² and is mounted on an axis,perpendicular to the magnetic field,which allows the loop to rotate.What is the torque on the loop when its plane is oriented at a 21° angle to the field?

A)2.4E-2 N⋅m
B)6.3E-2 N⋅m
C)3.7E-2 N⋅m
D)5.6E-2 N⋅m
E)9.4E-1 N⋅m

Question 80

A rectangular coil (0.13 m × 0.98 m)has 277 turns and is in a uniform magnetic field of 0.50 T.If the orientation of the coil is varied through all possible positions,the maximum torque on the coil by magnetic forces is 0.096 N⋅m.What is the current in the coil?

A)6.2E-4 A
B)1.5E+0 A
C)5.4E-3 A
D)4.2E+2 A
E)8.8E-5 A