Question 1

The magnetic force experienced by a charged particle always points

Accepted Answer

A) in the same direction as the magnetic field. 
B) in the opposite direction as the magnetic field. 
C) Either A or B is correct depending on the charge of the particle experiencing the force. 
D) None are correct. 
A) in the same direction as the magnetic field. 
B) in the opposite direction as the magnetic field. 
C) Either A or B is correct depending on the charge of the particle experiencing the force. 
D) None are correct. D

Question 2

An electron is traveling horizontally from E to W in a region of space where the Earth's magnetic field is directed horizontally toward the north.What is the direction of the magnetic force on the electron?

Accepted Answer

A) north 
B) south 
C) east 
D) up 
E) down 
A) north 
B) south 
C) east 
D) up 
E) down D

Question 3

In a copper wire,electrons move to the right.The direction of the magnetic field is toward you (out of the page).In which direction is the magnetic force on the copper wire?

Accepted Answer

A) to the top of the page 
B) to the bottom of the page 
C) into the page 
D) out of the page 
E) to the left 
A) to the top of the page 
B) to the bottom of the page 
C) into the page 
D) out of the page 
E) to the left A

Question 4

A straight wire of length 5.0 m carries a current I and it is placed on a horizontal table in a horizontal uniform magnetic field of magnitude 0.016 T.The wire makes an angle of 25S1U1P1$\circ$S1S1P0 with the magnetic field lines.If the magnitude of the magnetic force on the wire is 0.62 N,what is the current I?

Accepted Answer

A) 35 A 
B) 18 A 
C) 45 A 
D) 24 A 
E) 65 A 
A) 35 A 
B) 18 A 
C) 45 A 
D) 24 A 
E) 65 A

Question 5

A straight section of a current-bearing wire passes through a 15-cm wide region of space between the poles of an electromagnet.The magnetic field,when the electromagnet is on,is inclined at a 72 degree angle relative to the wire.If,when the magnet is turned on and produces a field of 1.0 T,the wire experiences a force of 0.18 N,what current is flowing in the wire?

Accepted Answer

A) 1.2 A 
B) 1.3 A 
C) 3.7 A 
D) 3.9 A 
E) None are correct. 
A) 1.2 A 
B) 1.3 A 
C) 3.7 A 
D) 3.9 A 
E) None are correct.

Question 6

Initially at rest,a small copper sphere with a mass of 2.0 * 10-6 kg and a charge of 3.0 *10-4 C is accelerated through a 5000 V potential difference before entering a region with a 4.0 T magnetic field that is directed perpendicular to the its velocity.What is the radius of curvature of the copper sphere's motion in the magnetic field region?

Accepted Answer

A) 2.0 m 
B) 4.1 m 
C) 8.3 m 
D) 650 m 
E) 1300 m 
A) 2.0 m 
B) 4.1 m 
C) 8.3 m 
D) 650 m 
E) 1300 m

Question 7

Find the magnetic field that produces a maximum torque of 3.14 Nm on a coil of wire with 22 loops a length of 30 cm and a width of 20 cm.The coil has a resistance of 50 ohms and is connected to a 120-V battery.

Accepted Answer

A) 0.020 T 
B) 0.048 T 
C) 0.99 T 
D) 5.7 T 
E) 22 T 
A) 0.020 T 
B) 0.048 T 
C) 0.99 T 
D) 5.7 T 
E) 22 T

Question 8

An electron with a speed of 6.00 * 105 m/s enters a uniform magnetic field of 0.0600 T at an angle $\theta$ to the magnetic field lines.The electron will travel in a helical path of radius 4.80 *10-5 m.Find the angle $\theta$.

Accepted Answer

A) 25.3S1U1P1$\circ$S1S1P0 
B) 32.3S1U1P1$\circ$S1S1P0 
C) 57.6S1U1P1$\circ$S1S1P0 
D) 61.4S1U1P1$\circ$S1S1P0 
A) 25.3S1U1P1$\circ$S1S1P0 
B) 32.3S1U1P1$\circ$S1S1P0 
C) 57.6S1U1P1$\circ$S1S1P0 
D) 61.4S1U1P1$\circ$S1S1P0

Question 9

Carbon-12 and Carbon-14 atoms,(12 and 14 atomic mass units,respectively)each missing one electron,so that they carry +1e electric charge,each are accelerated through the same electric potential and pass through a hole in a vertical lead plate into a region of uniform magnetic field,also oriented vertically.What is the ratio of the radii of curvature r12/r14 for these two atoms' paths?

Accepted Answer

A) 0.86 
B) 0.93 
C) 1.1 
D) 1.2 
E) You would need to know the potential through which they were accelerated. 
A) 0.86 
B) 0.93 
C) 1.1 
D) 1.2 
E) You would need to know the potential through which they were accelerated.

Question 10

A 20-cm long conducting wire of 5-g carrying 5-A current is placed in a uniform magnetic field.The strength and direction of the magnetic field needed to levitate the wire are

Accepted Answer

A) 49.05 mT into the page. 
B) 49.05 mT out of the page. 
C) 25 mT into the page. 
D) 25 mT out of the page. 
E) 15 mT into the page. 
A) 49.05 mT into the page. 
B) 49.05 mT out of the page. 
C) 25 mT into the page. 
D) 25 mT out of the page. 
E) 15 mT into the page.

Question 11

A cyclotron with a magnetic field of 9 T is used to accelerate protons with a speed of 50% the speed of light.What is the cyclotron frequency of these protons?

Accepted Answer

A) 225 MHz 
B) 137 MhZ 
C) 789 kHz 
D) 14 Mhz 
E) 25 kHz 
A) 225 MHz 
B) 137 MhZ 
C) 789 kHz 
D) 14 Mhz 
E) 25 kHz

Question 12

A positively charged rod is brought close to a freely suspended compass needle as shown in the figure.The compass needle will

Accepted Answer

A) rotate clockwise. 
B) rotate counterclockwise. 
C) not be affected. 
A) rotate clockwise. 
B) rotate counterclockwise. 
C) not be affected.

Question 13

The figure shown depicts the cross section of a current carrying ring of wire having a radius of 4 cm.A 1.25 A current flows in the ring in the direction indicated in the drawing.The ring is free to rotate,clockwise or counterclockwise,about an axis normal to the page which passes through its center.The ring is connected to a spring as shown.The spring is fixed to a wall at the other end.When the ring is in the vertical position,the spring is at its natural length.One may assume that the length of the spring is long enough such that any extension or compression follows Hooke's law.Determine the current in the loop if the magnitude of the change in length of the spring when a magnetic field B = 2 T applied along the vertical axis is 2.5 mm.

Accepted Answer

A) 125 N/m 
B) 133 N/m 
C) 100 N/m 
D) 150 N/m 
A) 125 N/m 
B) 133 N/m 
C) 100 N/m 
D) 150 N/m

Question 14

One of the first cyclotrons,built by Lawrence and Livingston in the 1930's,accelerated protons circles in the space between two magnetic poles.The magnetic poles were shaped like flat disks with a diameter of 25 cm and the magnetic field between the plates was uniform and oriented perpendicular to the plates.The plates and proton trajectories were horizontal.The plates were parallel to each other and separated by 5 cm.The protons started traveling slowly in small circles at the center of the disks,and would begin making larger and larger circles,travelling faster and faster,until they left the region between the plates.When the protons left the magnetic region at the edge of the plates,they were travelling at 1.2 *107 m/s.What was the magnetic field between the plates?

Accepted Answer

A) 0.50 T 
B) 0.75 T 
C) 1.0 T 
D) 1.25 T 
E) 1.5 T 
A) 0.50 T 
B) 0.75 T 
C) 1.0 T 
D) 1.25 T 
E) 1.5 T

Question 15

An electron enters a uniform magnetic field of 0.0600 T at an angle of 61.4S1U1P1$\circ$S1S1P0 to the magnetic field lines.The electron will travel in a helical path of radius 4.80 * 10-5 m.Find the speed of the electron.

Accepted Answer

A) 6.13 * 105 m/s 
B) 6.00 * 105 m/s 
C) 5.06 * 105 m/s 
D) 5.76 * 105 m/s 
A) 6.13 * 105 m/s 
B) 6.00 * 105 m/s 
C) 5.06 * 105 m/s 
D) 5.76 * 105 m/s

Question 16

A 30.0   C charged particle moves along the x-axis with a speed of 30.0 m/s.It enters a magnetic field given by   .Determine the magnitude of the magnetic force on the particle.

Accepted Answer

A) 1.72 * 10-4 N 
B) 2.31 * 10-4 N 
C) 4.69 * 10-4 N 
D) 5.25 * 10-4 N 
E) 6.34 * 10-4 N 
A) 1.72 * 10-4 N 
B) 2.31 * 10-4 N 
C) 4.69 * 10-4 N 
D) 5.25 * 10-4 N 
E) 6.34 * 10-4 N

Question 17

Hall probe is a device widely used for measuring magnetic field strengths.One Hall probe consists of a current carrying strip of bismuth that is 0.20 mm thick and 4 mm wide.The charge carrier density of bismuth is 1.35 * 1025 m-3.When the strip is placed in a magnetic field perpendicular to the direction of 2.1-A current,it develops a Hall voltage of 3.5 mV across the strip.The strength of the magnetic field is

Accepted Answer

A) 72 T. 
B) 8 T. 
C) 1.5 T. 
D) 0.72 T. 
E) 21 mT. 
A) 72 T. 
B) 8 T. 
C) 1.5 T. 
D) 0.72 T. 
E) 21 mT.

Question 18

The figure shown depicts the cross section of a current carrying ring of wire having a radius of 4 cm.A 1-A current flows in the ring in the direction indicated in the drawing.The ring is free to rotate,clockwise or counterclockwise,about an axis normal to the page which passes through its center.The ring is connected to a spring with a spring constant of 100 N/m as shown.The spring is fixed to a wall at the other end.When the ring is in the vertical position,the spring is at its natural length.One may assume that the length of the spring is long enough such that any extension or compression follows Hooke's law.If the magnitude of the change in length of the spring when a magnetic field B is applied along the vertical axis is 1.25 mm,what is the magnitude of the magnetic field?

Accepted Answer

A) 4.0 T 
B) 2.0 T 
C) 0.50 T 
D) 1.0 T 
A) 4.0 T 
B) 2.0 T 
C) 0.50 T 
D) 1.0 T

Question 19

An electron moving with velocity v to the right enters a region of uniform magnetic field that points out of the paper.After the electron enters the field,it will be

Accepted Answer

A) deflected out of the plane of the paper in the direction of the field. 
B) deflected into the plane of the paper opposite to the field. 
C) deflected downwards in the plane of the paper. 
D) deflected upward in the plane of the paper. 
E) undeviated. 
A) deflected out of the plane of the paper in the direction of the field. 
B) deflected into the plane of the paper opposite to the field. 
C) deflected downwards in the plane of the paper. 
D) deflected upward in the plane of the paper. 
E) undeviated.

Question 20

An electron traveling with a velocity of 6.0 * 105 m/s along the   direction enters a uniform magnetic field of 0.60 T pointing in the   direction.The magnitude of the force on the electron is

Accepted Answer

A) 2.6 * 10-14 N. 
B) 5.8 * 10-14 N. 
C) 8.5 * 10-14 N. 
D) 9.4 * 10-14 N. 
A) 2.6 * 10-14 N. 
B) 5.8 * 10-14 N. 
C) 8.5 * 10-14 N. 
D) 9.4 * 10-14 N.

Exam 27: Magnetism

The magnetic force experienced by a charged particle always points

An electron is traveling horizontally from E to W in a region of space where the Earth's magnetic field is directed horizontally toward the north.What is the direction of the magnetic force on the electron?

In a copper wire,electrons move to the right.The direction of the magnetic field is toward you (out of the page).In which direction is the magnetic force on the copper wire?

Find the magnetic field that produces a maximum torque of 3.14 Nm on a coil of wire with 22 loops a length of 30 cm and a width of 20 cm.The coil has a resistance of 50 ohms and is connected to a 120-V battery.

An electron with a speed of 6.00 * 105 m/s enters a uniform magnetic field of 0.0600 T at an angle θ\thetaθ to the magnetic field lines.The electron will travel in a helical path of radius 4.80 *10-5 m.Find the angle θ\thetaθ .

A 20-cm long conducting wire of 5-g carrying 5-A current is placed in a uniform magnetic field.The strength and direction of the magnetic field needed to levitate the wire are

A cyclotron with a magnetic field of 9 T is used to accelerate protons with a speed of 50% the speed of light.What is the cyclotron frequency of these protons?

A positively charged rod is brought close to a freely suspended compass needle as shown in the figure.The compass needle will

An electron enters a uniform magnetic field of 0.0600 T at an angle of 61.4 ∘\circ∘ to the magnetic field lines.The electron will travel in a helical path of radius 4.80 * 10-5 m.Find the speed of the electron.

A 30.0 C charged particle moves along the x-axis with a speed of 30.0 m/s.It enters a magnetic field given by .Determine the magnitude of the magnetic force on the particle.

An electron moving with velocity v to the right enters a region of uniform magnetic field that points out of the paper.After the electron enters the field,it will be

An electron traveling with a velocity of 6.0 * 105 m/s along the direction enters a uniform magnetic field of 0.60 T pointing in the direction.The magnitude of the force on the electron is

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An electron with a speed of 6.00 * 10⁵ m/s enters a uniform magnetic field of 0.0600 T at an angle $\theta$ to the magnetic field lines.The electron will travel in a helical path of radius 4.80 *10^-5 m.Find the angle $\theta$ .

An electron enters a uniform magnetic field of 0.0600 T at an angle of 61.4^$\circ$ to the magnetic field lines.The electron will travel in a helical path of radius 4.80 * 10^-5 m.Find the speed of the electron.

An electron traveling with a velocity of 6.0 * 10⁵ m/s along the direction enters a uniform magnetic field of 0.60 T pointing in the direction.The magnitude of the force on the electron is