Question 1

A vertical wire carries a current vertically downward. To the east of this wire, the magnetic field points

Accepted Answer

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

Question 2

Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 0.20 m. What is the strength of the magnetic field midway between the two wires? (μ0 = 4π × 10-7 T ∙ m/A)

Accepted Answer

A) 1.0 × 10-5 T 
B) 2.0 × 10-5 T 
C) 3.0 × 10-5 T 
D) 4.0 × 10-5 T 
E) 5.0 × 10-5 T 
A) 1.0 × 10-5 T 
B) 2.0 × 10-5 T 
C) 3.0 × 10-5 T 
D) 4.0 × 10-5 T 
E) 5.0 × 10-5 T

Question 3

A proton travels at a speed of 5.0 × 107 m/s through a 1.0-T magnetic field. What is the magnitude of the magnetic force on the proton if the angle between the proton's velocity and the magnetic field vector is 30°? (e = 1.60 × 10-19 C

Accepted Answer

A) 2.0 × 10-14 N 
B) 4.0 × 10-14 N 
C) 2.0 × 10-12 N 
D) 4.0 × 10-12 N 
A) 2.0 × 10-14 N 
B) 4.0 × 10-14 N 
C) 2.0 × 10-12 N 
D) 4.0 × 10-12 N

Question 4

A wire is carrying current vertically downward. What is the direction of the force on this wire due to Earth's magnetic field?

Accepted Answer

A) horizontally towards the north 
B) horizontally towards the south 
C) horizontally towards the east 
D) horizontally towards the west 
E) vertically upward 
A) horizontally towards the north 
B) horizontally towards the south 
C) horizontally towards the east 
D) horizontally towards the west 
E) vertically upward

Question 5

A proton is to orbit Earth at the equator using Earth's magnetic field to supply part of the necessary centripetal force. In what direction should the proton move?

Accepted Answer

A) upward 
B) northward 
C) southward 
D) eastward 
E) westward 
A) upward 
B) northward 
C) southward 
D) eastward 
E) westward

Question 6

A rectangular coil, with corners labeled ABCD, has length L and width w. It is placed between the poles of a magnet, as shown in the figure If there is a current I flowing through this coil in the direction shown, what is the direction of the force acting on section BC of this coil?

Accepted Answer

A) perpendicular to and into the page 
B) perpendicular to and out of the page 
C) in the direction of the magnetic field 
D) in the opposite direction of the magnetic field 
E) The force is zero. 
A) perpendicular to and into the page 
B) perpendicular to and out of the page 
C) in the direction of the magnetic field 
D) in the opposite direction of the magnetic field 
E) The force is zero.

Question 7

A long, straight, horizontal wire carries current toward the east. An electron moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the electron?

Accepted Answer

A) toward the north 
B) toward the south 
C) upward 
D) downward 
E) toward the west 
A) toward the north 
B) toward the south 
C) upward 
D) downward 
E) toward the west

Question 8

Two long parallel wires are placed side-by-side on a horizontal table and carry current in the same direction. The current in one wire is 20 A, and the current in the other wire is 5 A. If the magnetic force on the 20-A wire has magnitude F, what is the magnitude of the magnetic force on the 5-A wire? No external magnetic fields are present.

Accepted Answer

A) 4F 
B) 2F 
C) F 
D) F/2 
E) F/4 
A) 4F 
B) 2F 
C) F 
D) F/2 
E) F/4

Question 9

A long wire carrying a 2.0-A current is placed along the y-axis. What is the magnitude of the magnetic field at a point that is 0.60 m from the origin along the x-axis? (μ0 = 4π × 10-7 T ∙ m/A)

Accepted Answer

A) 0.67 µT 
B) 1.3 µT 
C) 0.12 µT 
D) 6.7 T 
E) 12 T 
A) 0.67 µT 
B) 1.3 µT 
C) 0.12 µT 
D) 6.7 T 
E) 12 T

Question 10

The magnetic force on a current-carrying wire in a magnetic field is the strongest when

Accepted Answer

A) the current is in the direction of the magnetic field lines. 
B) the current is in the direction opposite to the magnetic field lines. 
C) the current is at a 180° angle with respect to the magnetic field lines. 
D) the current is perpendicular to the magnetic field lines. 
E) the current is at a 0° angle with respect to the magnetic field lines. 
A) the current is in the direction of the magnetic field lines. 
B) the current is in the direction opposite to the magnetic field lines. 
C) the current is at a 180° angle with respect to the magnetic field lines. 
D) the current is perpendicular to the magnetic field lines. 
E) the current is at a 0° angle with respect to the magnetic field lines.

Question 11

A wire in the shape of an "M" lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E. It is placed in a uniform magnetic field of 0.85 T in the same plane, directed as shown on the right side of the figure. The figure indicates the dimensions of the wire. Note that AB is parallel to DE and to the baseline from which the magnetic field direction is measured. What are the magnitude and direction of the net force acting on this wire?

Accepted Answer

A) 0.40 N perpendicular out of the page 
B) 0.10 N perpendicular into the page 
C) 0.40 N perpendicular into the page 
D) 0.10 N perpendicular out of the page 
E) 0.20 N perpendicular out of the page 
A) 0.40 N perpendicular out of the page 
B) 0.10 N perpendicular into the page 
C) 0.40 N perpendicular into the page 
D) 0.10 N perpendicular out of the page 
E) 0.20 N perpendicular out of the page

Question 12

The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 μT. What is the magnetic field at a distance of 1 cm from this wire?

Accepted Answer

A) 2 μT 
B) 4 μT 
C) 6 μT 
D) 8 μT 
E) 10 μT 
A) 2 μT 
B) 4 μT 
C) 6 μT 
D) 8 μT 
E) 10 μT

Question 13

A long straight wire carrying a 4-A current is placed along the x-axis as shown in the figure. What is the direction of the magnetic field at a point P due to this wire?

Accepted Answer

A) into the plane of the page 
B) out of the plane of the page 
C) along the -x-axis 
D) along the +x-axis 
E) along the +y-axis 
A) into the plane of the page 
B) out of the plane of the page 
C) along the -x-axis 
D) along the +x-axis 
E) along the +y-axis

Question 14

A wire lying in the plane of the page carries a current toward the bottom of the page, as shown in the figure. What is the direction of the magnetic force it produces on an electron that is moving to the left directly toward the wire, as shown?

Accepted Answer

A) straight into the page 
B) straight out of the page 
C) directly toward the top of the page 
D) directly toward the bottom of the page 
E) directly to the left away from the wire 
A) straight into the page 
B) straight out of the page 
C) directly toward the top of the page 
D) directly toward the bottom of the page 
E) directly to the left away from the wire

Question 15

Which one of the following statements is correct?

Accepted Answer

A) Earth's geographic north pole is the north pole of Earth's magnetic field. 
B) Earth's geographic south pole is the south pole of Earth's magnetic field. 
C) The north pole of a magnet points towards Earth's geographic north pole. 
D) The north pole of a magnet points towards Earth's geographic south pole. 
E) None of the above statements is correct. 
A) Earth's geographic north pole is the north pole of Earth's magnetic field. 
B) Earth's geographic south pole is the south pole of Earth's magnetic field. 
C) The north pole of a magnet points towards Earth's geographic north pole. 
D) The north pole of a magnet points towards Earth's geographic south pole. 
E) None of the above statements is correct.

Question 16

An electron moving perpendicular to a uniform magnetic field of 3.2 × 10-2 T moves in a circle of radius 0.40 cm. How fast is this electron moving? (e = 1.60 × 10-19 C, melectron = 9.11 × 10-31kg)

Accepted Answer

A) 2.2 × 107 m/s 
B) 1.9 × 107 m/s 
C) 1.9 × 106 m/s 
D) 3.0 × 107 m/s 
E) 0.80 × 107 m/s 
A) 2.2 × 107 m/s 
B) 1.9 × 107 m/s 
C) 1.9 × 106 m/s 
D) 3.0 × 107 m/s 
E) 0.80 × 107 m/s

Question 17

A wire lying in the plane of this page carries a current directly toward the top of the page. What is the direction of the magnetic force this current produces on an electron that is moving perpendicular to the page and outward from it on the left side of the wire?

Accepted Answer

A) perpendicular to the page and towards you 
B) perpendicular to the page and away from you 
C) toward the top of the page 
D) toward the bottom of the page 
E) The force is zero. 
A) perpendicular to the page and towards you 
B) perpendicular to the page and away from you 
C) toward the top of the page 
D) toward the bottom of the page 
E) The force is zero.

Question 18

A single current-carrying circular loop of radius R is placed next to a long, straight wire, as shown in the figure. The current I in the wire flows to the right. In which direction must current flow in the loop to produce a net magnetic field of zero at its center?

Accepted Answer

A) counterclockwise 
B) clockwise 
C) It could be either clockwise or counterclockwise. 
D) The current in the loop should be zero. 
A) counterclockwise 
B) clockwise 
C) It could be either clockwise or counterclockwise. 
D) The current in the loop should be zero.

Question 19

An electron is accelerated from rest through a potential difference of 3.75 kV. It enters a region where a uniform 4.0-mT magnetic field is perpendicular to the velocity of the electron. Calculate the radius of the path this electron will follow in the magnetic field. (e = 1.60 × 10-19 C, melectron = 9.11 × 10-31 kg)

Accepted Answer

A) 1.2 cm 
B) 2.2 cm 
C) 3.2 cm 
D) 4.2 cm 
E) 5.2 cm 
A) 1.2 cm 
B) 2.2 cm 
C) 3.2 cm 
D) 4.2 cm 
E) 5.2 cm

Question 20

A flat rectangular loop of wire is placed between the poles of a magnet, as shown in the figure. It has dimensions w = 0.60 m and L = 1.0 m, and carries a current I = 2.0 A in the direction shown. The magnetic field due to the magnet is uniform and of magnitude 0.80 T.
- The loop rotates in the magnetic field and at one point the plane of the loop is perpendicular to the field. At that instant, what is the magnitude of the torque acting on the wire due to the magnetic field?

Accepted Answer

A) 0.00 N ? m 
B) 0.40 N ? m 
C) 0.48 N ? m 
D) 0.83 N ? m 
E) 0.96 N ? m 
A) 0.00 N ? m 
B) 0.40 N ? m 
C) 0.48 N ? m 
D) 0.83 N ? m 
E) 0.96 N ? m

Exam 24: Magnetic Fields and Forces

A vertical wire carries a current vertically downward. To the east of this wire, the magnetic field points

Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 0.20 m. What is the strength of the magnetic field midway between the two wires? (μ0 = 4π × 10-7 T ∙ m/A)

A proton travels at a speed of 5.0 × 107 m/s through a 1.0-T magnetic field. What is the magnitude of the magnetic force on the proton if the angle between the proton's velocity and the magnetic field vector is 30°? (e = 1.60 × 10-19 C

A wire is carrying current vertically downward. What is the direction of the force on this wire due to Earth's magnetic field?

A proton is to orbit Earth at the equator using Earth's magnetic field to supply part of the necessary centripetal force. In what direction should the proton move?

A rectangular coil, with corners labeled ABCD, has length L and width w. It is placed between the poles of a magnet, as shown in the figure If there is a current I flowing through this coil in the direction shown, what is the direction of the force acting on section BC of this coil?

A long, straight, horizontal wire carries current toward the east. An electron moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the electron?

A long wire carrying a 2.0-A current is placed along the y-axis. What is the magnitude of the magnetic field at a point that is 0.60 m from the origin along the x-axis? (μ0 = 4π × 10-7 T ∙ m/A)

The magnetic force on a current-carrying wire in a magnetic field is the strongest when

The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 μT. What is the magnetic field at a distance of 1 cm from this wire?

A long straight wire carrying a 4-A current is placed along the x-axis as shown in the figure. What is the direction of the magnetic field at a point P due to this wire?

A wire lying in the plane of the page carries a current toward the bottom of the page, as shown in the figure. What is the direction of the magnetic force it produces on an electron that is moving to the left directly toward the wire, as shown?

Which one of the following statements is correct?

An electron moving perpendicular to a uniform magnetic field of 3.2 × 10-2 T moves in a circle of radius 0.40 cm. How fast is this electron moving? (e = 1.60 × 10-19 C, melectron = 9.11 × 10-31kg)

A wire lying in the plane of this page carries a current directly toward the top of the page. What is the direction of the magnetic force this current produces on an electron that is moving perpendicular to the page and outward from it on the left side of the wire?

A single current-carrying circular loop of radius R is placed next to a long, straight wire, as shown in the figure. The current I in the wire flows to the right. In which direction must current flow in the loop to produce a net magnetic field of zero at its center?

Representing Motion

Motion in One Dimension

Vectors and Motion in Two Dimensions

Forces and Newtons Laws of Motion

Applying Newtons Laws

Gravity

Rotational Motion

Equilibrium Ad Elasticity

Momentum

Energy and Work

Using Energy

Thermal Properties of Matter

Fluids

Oscillations

Traveling Waves and Sound

Superposition and Standing Waves

Wave Optics

Ray Optics

Optical Instruments

Electric Fields and Forces

Electric Potential

Current and Resistance

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Em Induction and Em Waves

Ac Electricity

Relativity

Quantum Physics

Atoms and Molecules

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Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 0.20 m. What is the strength of the magnetic field midway between the two wires? (μ₀ = 4π × 10^-7 T ∙ m/A)

A proton travels at a speed of 5.0 × 10⁷ m/s through a 1.0-T magnetic field. What is the magnitude of the magnetic force on the proton if the angle between the proton's velocity and the magnetic field vector is 30°? (e = 1.60 × 10^-19 C

A long wire carrying a 2.0-A current is placed along the y-axis. What is the magnitude of the magnetic field at a point that is 0.60 m from the origin along the x-axis? (μ₀ = 4π × 10^-7 T ∙ m/A)

An electron moving perpendicular to a uniform magnetic field of 3.2 × 10^-2 T moves in a circle of radius 0.40 cm. How fast is this electron moving? (e = 1.60 × 10^-19 C, m_electron = 9.11 × 10^-31kg)