Chapter 20

A rigid rectangular loop, measuring 0.30 m by 0.40 m, carries a current of 9.9 A, as shown in the figure. A uniform external magnetic field of magnitude 1.8 T in the -x direction is present. Segment CD is in the xz-plane and forms a 19° angle with the z-axis, as shown. What is the y component of the magnetic force on segment AB of the loop? (Figure from Q104)

+5.1 N

An electron moving in the +y direction, at right angles to a magnetic field, experiences a magnetic force in the -x direction. The direction of the magnetic field is in the

+z direction.

A proton is projected with a velocity of 7.0 km/s into a magnetic field of 0.60 T perpendicular to the motion of the proton. What is the magnitude of the magnetic force that acts on the proton? (e = 1.60 × 10^-19 C)

0 N

A wire in the shape of an ʺMʺ lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E, as shown in the figure. It is placed in a uniform magnetic field of0.65 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 force acting on section BC of this wire? (Figure from Q109)

0 N

A flat circular loop of wire of radius 0.50 m that is carrying a 2.0-A current is in a uniform magnetic field of 0.30 T. What is the magnitude of the magnetic torque on the loop when the plane of its area is perpendicular to the magnetic field?

0.00 N · m

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? (Figure from Q125)

0.00 N · m

A charged particle of mass 0.0040 kg is subjected to a 4.0-T magnetic field which acts at a right angle to its motion. If the particle moves in a circle of radius 0.10 m at a speed of 2.0 m/s, what is the magnitude of the charge on the particle?

0.020 C

What is the force per meter on a straight wire carrying 5.0 A when it is placed in a magnetic field of 0.020 T so that the wire makes an angle of 27° with respect to the magnetic field lines.

0.045 N/m

A wire in the shape of an ʺMʺ lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E, as shown in the figure. It is placed in a uniform magnetic field of 0.55 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 force acting on section CD of this wire? (Figure from Q110)

0.066 N perpendicular out of the page

A wire in the shape of an ʺMʺ 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? (Figure from Q112)

0.10 N perpendicular out of the page

A wire in the shape of an ʺMʺ lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E, as shown in the figure. It is placed in a uniform magnetic field of0.75 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 force acting on section AB of this wire? (Figure from Q108)

0.11 N perpendicular out of the page

A proton, starting from rest, accelerates through a potential difference of 1.0 kV and then moves into a magnetic field of 0.040 T at a right angle to the field. What is the radius of the protonʹs resulting orbit? (e = 1.60 × 10^-19 C, mproton = 1.67 × 10^-27 kg)

0.11 m

A wire in the shape of an ʺMʺ lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E, as shown in the figure. It is placed in a uniform magnetic field of0.85 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 force acting on section DE of this wire? (Figure from Q111)

0.12 N perpendicular into the page

Alpha particles, each having a charge of +2e and a mass of 6.64 ×10-27 kg, are accelerated in a uniform 0.80-T magnetic field to a final orbit radius of 0.30 m. The field is perpendicular to the velocity of the particles. How long does it take an alpha particle to make one complete circle in the final orbit? (e = 1.60 × 10-19 C)

0.15 μs

A proton having a speed of 3.0 × 106 m/s in a direction perpendicular to a uniform magnetic field moves in a circle of radius 0.20 m within the field. What is the magnitude of the magnetic field? (e = 1.60 × 10^-19 C, mproton = 1.67 × 10^-27 kg)

0.16 T

An ideal solenoid 20 cm long is wound with 5000 turns of very thin wire. What strength magnetic field is produced at the center of the solenoid when a current of 10 A flows through it?(μ0 = 4π × 10^-7 T · m/A)

0.31 T

A flat circular loop of wire is in a uniform magnetic field of 0.30 T. The diameter of the loop is 1.0 m, and a 2.0-A current flows in it. What is the magnitude of the magnetic torque on the loop when the plane of the loop is parallel to the magnetic field?

0.47 N · m

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 makes a 30° angle with the field. At that instant, what is the magnitude of the torque acting on the wire due to the magnetic field? (Figure from Q123)

0.48 N · m

A flat circular coil has 200 identical loops of very thin wire. Each loop has an area of 0.12 m2 and carries 0.50 A of current. This coil is placed in a magnetic field of 0.050 T oriented at 30° to the plane of the loop. What is the magnitude of the magnetic torque on the coil?

0.52 N · m

A flat rectangular loop of wire carrying a 4.0-A current is placed in a uniform 0.60-T magnetic field. The magnitude of the torque acting on this loop when the plane of the loop makes a 30° angle with the field is measured to be 1.1 N · m. What is the area of this loop?

0.53 m^2

A flat circular loop carrying a current of 2.0 A is in a magnetic field of 3.5 T. The loop has an area of 0.12 m2 and its plane is oriented at a 37° angle to the field. What is the magnitude of the magnetic torque on the loop?

0.67 N · m

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)

0.67 μT

A straight wire carries a current of 10 A at an angle of 30° with respect to the direction of a uniform 0.30-T magnetic field. Find the magnitude of the magnetic force on a 0.50-m length of the wire.

0.75 N

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 parallel to the field. At that instant, what is the magnitude of the torque acting on the wire due to the magnetic field? (Figure from Q124)

0.96 N · m

The maximum torque on a flat current-carrying loop occurs when the angle between the plane of the loopʹs area and the magnetic field vector is

0°

Three particles travel through a region of space where the magnetic field is out of the page, as shown in the figure. What are the signs of the charges of these three particles? (figure from Q13)

1 is negative, 2 is neutral, and 3 is positive.

A very long thin wire produces a magnetic field of 0.0020 × 10^-4 T at a distance of 1.0 mm from the wire. What is the magnitude of the current? (μ0 = 4π × 10^-7 T · m/A)

1.0 mA

A rigid rectangular loop, measuring 0.30 m by 0.40 m, carries a current of 5.5 A, as shown in the figure. A uniform external magnetic field of magnitude 2.9 T in the -x direction is present. Segment CD is in the xz-plane and forms a 35° angle with the z-axis, as shown. What is the magnitude of the torque that the magnetic field exerts on the loop?

1.1 N · m

A proton moving with a velocity of 4.0 × 104 m/s enters a magnetic field of 0.20 T. If the angle between the velocity of the proton and the direction of the magnetic field is 60°, what is the magnitude of the magnetic force on the proton? (e = 1.60 × 10^-19 C)

1.1 × 10^-15 N

A straight wire is carrying a current of 2.0 A. It is placed at an angle of 60° with respect to a magnetic field of strength 0.20 T. If the wire experiences a force of 0.40 N, what is the length of the wire?

1.2 m

A proton moving with a velocity of 4.0 × 104 m/s along the +y-axis enters a magnetic field of 0.20 T directed towards the -x-axis. What is the magnitude of the magnetic force acting on the proton? (e = 1.60 × 10^-19 C)

1.3 × 10^-15 N

The magnetic field due to the current in a long, straight wire is 8.0 μT at a distance of 4.0 cm from the center of the wire. What is the current in the wire? (μ0 = 4π × 10^-7 T · m/A)

1.6 A

An ideal solenoid of length 10 cm consists of a wire wrapped tightly around a wooden core. The magnetic field strength is 4.0 T inside the solenoid. If the solenoid is stretched to25 cm by applying a force to it, what does the magnetic field become?

1.6 T

An electron moves with a speed of 5.0 × 104 m/s perpendicular to a uniform magnetic field of magnitude 0.20 T. What is the magnitude of the magnetic force on the electron? (e = 1.60 × 10^-19 C)

1.6 × 10-15 N

A proton moving eastward with a velocity of 5.0 km/s enters a magnetic field of 0.20 T pointing northward. What are the magnitude and direction of the force that the magnetic field exerts on the proton? (e = 1.60 × 10^-19 C)

1.6 × 10^-16 N upwards

A beam of electrons is accelerated through a potential difference of 1.0 kV before entering a velocity selector. If the magnetic field of the velocity selector has a magnitude of 0.010 T, what magnitude of the electric field is required if the electrons are not to be deflected as they pass through the velocity selector? ((e = 1.60 × 10^-19 C, melectron = 9.11 × 10^-31 kg)

1.9 × 105 V/m

An electron moves with a speed of 3.0 × 104 m/s perpendicular to a uniform magnetic field of 0.40 T. What is the magnitude of the magnetic force on the electron? (e = 1.60 × 10^-19 C)

1.9 × 10^-15 N

A doubly charged ion with speed 6.9 × 106 m/s enters a uniform 0.80-T magnetic field, traveling perpendicular to the field. Once in the field, it moves in a circular arc of radius 30 cm. What is the mass of this ion? (e = 1.60 × 10^-19 C)

11 × 10^-27 kg

Two long parallel wires are 0.400 m apart and carry currents of 4.00 A and 6.00 A. What is the magnitude of the force per unit length that each wire exerts on the other wire? (μ0 = 4π × 10-7 T · m/A)

12.0 μN/m

How many turns should a 10-cm long ideal solenoid have if it is to generate a 1.5-mT magnetic field when 1.0 A of current runs through it? (μ0 = 4π × 10-7 T · m/A)

120

An ideal solenoid that is 34.0 cm long is carrying a current of 2.00 A. If the magnitude of the magnetic field generated at the center of the solenoid is 9.00 mT, how many turns of wire does this solenoid contain? (μ0 = 4π × 10-7 T · m/A)

1220

The figure shows a velocity selector that can be used to measure the speed of a charged particle. A beam of particles of charge +q is directed along the axis of the instrument. A parallel plate capacitor sets up an electric field E which is oriented perpendicular to a uniform magnetic field B. If the plates are separated by 3.0 mm and the value of the magnetic field is 0.30 T, what potential difference between the plates will allow particles of speed v = 5.0 × 10^5 m/s to pass straight through without deflection? (From figure Q163)

1400 V

An ideal solenoid with 400 turns has a radius of 0.040 m and is 40 cm long. If this solenoid carries a current of 12 A, what is the magnitude of the magnetic field at the center of the solenoid? (μ0 = 4π × 10^-7 T · m/A)

15 mT

How much current must flow through a long straight wire for the magnetic field strength to be 1.0 mT at 1.0 cm from a wire? (μ0 = 4π × 10^-7 T · m/A)

16 A

Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 20 cm. At what point between the two wires do they produce the same strength magnetic field?

16 cm from the 20 A wire

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 4 cm from this wire?

2 μT

At what distance from a long straight wire carrying a current of 5.0 A is the magnitude of the magnetic field due to the wire equal to the strength of Earthʹs magnetic field of about 5.0× 10-5 T? (μ0 = 4π × 10^-7 T · m/A)

2.0 cm

A flat circular coil of wire having 200 turns and diameter 6.0 cm carries a current of 7.0 A. It is placed in a magnetic field of 0.60 T with the plane of the coil making an angle of 30° with the magnetic field. What is the magnitude of the magnetic torque on the coil?

2.1 N · m

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)

2.2 × 10^7 m/s

What is the magnetic moment of a rectangular loop having 120 turns that carries 6.0 A if its dimensions are 4.0 cm × 8.0 cm?

2.3 A · m^2

Two long parallel wires that are 0.30 m apart carry currents of 5.0 A and 8.0 A in the opposite direction. Find the magnitude of the force per unit length that each wire exerts on the other wire and indicate if the force is attractive or repulsive. (μ0 = 4π × 10-7 T · m/A)

2.7 × 10-5 N repulsive

An electron moves with a speed of 8.0 × 10^6 m/s along the +x-axis. It enters a region where there is a magnetic field of 2.5 T, directed at an angle of 60° to the +x-axis and lying in the xy-plane. Calculate the magnitude of the magnetic force on the electron. (e = 1.60 × 10^-19 C)

2.8 × 10^-12 N

A high power line carries a current of 1.0 kA. What is the strength of the magnetic field this line produces at the ground, 10 m away? (μ0 = 4π × 10^-7 T · m/A)

20 μT

Three long parallel wires each carry 2.0-A currents in the same direction. The wires are oriented vertically, and they pass through three of the corners of a horizontal square of side 4.0 cm. What is the magnitude of the magnetic field at the fourth (unoccupied) corner of the square due to these wires? (μ0 = 4π × 10^-7 T · m/A)

21 μT

An ideal solenoid having a coil density of 5000 turns per meter is 10 cm long and carries a current of 4.0 A. What is the strength of the magnetic field at its center?

25 mT

A charged particle is observed traveling in a circular path of radius R in a uniform magnetic field. If the particle were traveling twice as fast, the radius of the circular path would be

2R.

A straight 1.0-m long wire is carrying a current. The wire is placed perpendicular to a magnetic field of strength 0.20 T. If the wire experiences a force of 0.60 N, what is the current in the wire?

3.0 A

Alpha particles, each having a charge of +2e and a mass of 6.64 ×10-27 kg, are accelerated in a uniform 0.50 T magnetic field to a final orbit radius of 0.50 m. The field is perpendicular to the velocity of the particles. What is the kinetic energy of an alpha particle in the final orbit? (1 eV= 1.60 × 10-19 J, e = 1.60 × 10-19 C)

3.0 MeV

An electron moves with a speed of 8.0 × 106 m/s along the +x-axis. It enters a region where there is a magnetic field of 2.5 T, directed at an angle of 60° to the +x-axis and lying in the xy-plane. Calculate the magnitude of the acceleration of the electron. (e = 1.60 × 10^-19 C, me1 = 9.11 × 10^-31 kg)

3.0 × 10^18 m/s^2

An ideal solenoid is wound with 470 turns on a wooden form that is 4.0 cm in diameter and 50 cm long. The windings carry a current in the sense shown in the figure. The current produces a magnetic field of magnitude 4.1 mT, at the center of the solenoid.What is the current I in the solenoid windings? (μ0 = 4π × 10^-7 T · m/A) (Figure from Q160)

3.5 A

The magnitude of the magnetic field that a long and extremely thin current-carrying wire produces at a distance of 3.0 μm from the center of the wire is 2.0 × 10^-3 T. How much current is flowing through the wire? (μ0 = 4π × 10-7 T · m/A)

30 mA

A straight wire that is 0.60 m and carrying a current of 2.0 A is placed at an angle with respect to the magnetic field of strength 0.30 T. If the wire experiences a force of magnitude 0.18 N, what angle does the wire make with respect to the magnetic field?

30°

At point P the magnetic field due to a long straight wire carrying a current of 2.0 A is 1.2 μT. How far is P from the wire? (μ0 = 4π × 10^-7 T · m/A)

33 cm

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 protonʹs velocity and the magnetic field vector is 30°? (e = 1.60 × 10^-19 C)

4.0 × 10-12 N

A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to balance the weight of the rod?

4.9 A

A long straight wire carrying a 4-A current is placed along the x-axis as shown in the figure. What is the magnitude of the magnetic field at a point P, located at y = 2 cm, due to the current in this wire? (μ0 = 4π × 10^-7 T · m/A) (Figure from Q138)

40 μT

Two parallel straight wires are 7.0 cm apart and 50 m long. Each one carries a 18-A current in the same direction. One wire is securely anchored, and the other is attached in the center to a movable cart. If the force needed to move the wire when it is not attached to the cart is negligible, with what magnitude force does the wire pull on the cart? (μ0 = 4π × 10-7 T · m/A)

46 mN

When two long parallel wires carry unequal currents, the magnitude of the magnetic force that one wire exerts on the other is F. If the current in both wires is now doubled, what is the magnitude of the new magnetic force on each wire?

4F

A very long straight current-carrying wire produces a magnetic field of 20 mT at a distance d from the wire. To measure a field of 5 mT due to this wire, you would have to go to a distance from the wire of

4d.

The magnetic field at point P due to a 2.0-A current flowing in a long, straight, thin wire is 8.0 μT. How far is point P from the wire? (μ0 = 4π × 10^-7 T · m/A)

5.0 cm

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)

5.0 × 10-5 T

An electron moving perpendicular to a uniform magnetic field of 0.22 T moves in a circle with a speed of 1.5 × 10^7 m/s. What is the radius of the circle? (e = 1.60 × 10-19 C, melectron = 9.11 × 10^-31kg)

5.2 cm

Three very long, straight, parallel wires each carry currents of 4.0 A, directed out of the page as shown in the figure. These wires pass through the vertices of a right isosceles triangle as shown. Assume that all the quantities shown in the figure are accurate to two significant figures. What is the magnitude of the magnetic field at point P at the midpoint of the hypotenuse of the triangle? (μ0 = 4π × 10^-7 T · m/A) (Figure from Q150)

57 μT

In a mass spectrometer, a single-charged particle has a speed of 1.00 × 10^6 m/s and enters a uniform magnetic field of 0.200 T at a right angle to the field. The radius of the resulting circular orbit is 20.75 cm. What is the mass of the particle? (e = 1.60 × 10^-19 C)

6.64 × 10-27 kg

Two long parallel wires that are 0.40 m apart carry currents of 10 A in opposite directions. What is the magnetic field strength in the plane of the wires at a point that is 20 cm from one wire and 60 cm from the other? (μ0 = 4π × 10-7 T · m/A)

6.7 μT

A flat circular wire loop of area 0.25 m2 carries a current of 5.0 A. This coil lies on a horizontal table with the current flowing in the counterclockwise direction when viewed from above. At this point, the earthʹs magnetic field is 1.2 × 10^-5 T directed 60° below the horizontal. What is the magnitude of the torque that the earthʹs magnetic field exerts on this loop?

7.5 × 10-6 N · m

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?

8 μT

How much current must pass through a 400-turn ideal solenoid that is 4.0 cm long to generate a 1.0-T magnetic field at the center? (μ0 = 4π × 10^-7 T · m/A)

80 A

The figure shows a mass spectrograph that is operated with deuterons, which have a charge of+e and a mass of 3.34 × 10^-27 kg. The deuterons emerge with negligible velocity from the source, which is grounded. The speed of the deuterons as they pass through the accelerator grid is 8.0× 10^5 m/s. A uniform magnetic field of magnitude B = 0.20 T, directed out of the plane, is present to the right of the grid and is perpendicular to the velocity of the deuterons. The deuterons make a circular orbit in the magnetic field. What is the radius of this orbit, and what is the initial direction of their deflection just as they enter the magnetic field? (e = 1.60 × 10^-19 C) (From figure Q161)

84 mm, downward

Which of the following are units for the magnetic moment? (There could be more than one correct choice.) A) (T)/(N · m) B) (T)/(m^2) C) (N · m)/(T) D) A · m^2

C) (N · m)/(T) D) A · m^2

Which one of the following statements is correct? A) The north pole of a magnet points towards Earthʹs geographic south pole. B) Earthʹs geographic south pole is the south pole of Earthʹs magnetic field. C) The north pole of a magnet points towards Earthʹs geographic north pole. D) Earthʹs geographic north pole is the north pole of Earthʹs magnetic field. E) None of the above statements is correct.

C) The north pole of a magnet points towards Earthʹs geographic north pole.

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.

F

Two long, parallel wires carry currents of different magnitudes. If the amount of current in one of the wires is doubled, what happens to the magnitude of the force that each wire exerts on the other?

It is increased by a factor of 2.

Two long, parallel wires carry currents of different magnitudes. If the current in one of the wires is doubled and the current in the other wire is halved, what happens to the magnitude of the magnetic force that each wire exerts on the other?

It stays the same.

A particle carrying a charge of +e travels in a circular path of radius R in a uniform magnetic field. If instead the particle carried a charge of +2e, the radius of the circular path would have been

R/2.

A proton, moving in a uniform magnetic field, moves in a circle perpendicular to the field lines and takes time T for each circle. If the protonʹs speed tripled, what would now be its time to go around each circle?

T

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 currentI flowing through this coil in the direction shown, what is the direction of the force acting on section BC of this coil? (Figure from question Q35)

The force is zero.

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?

The force is zero.

A long straight wire has a constant current flowing to the right. A rectangular metal loop is situated above the wire, and also has a constant current flowing through it, as shown in the figure. Which one of the following statements is true? (Figure from Q68)

The net magnetic force on the rectangle is downward, and the net torque on it is zero.

A charged particle moving along the +x-axis enters a uniform magnetic field pointing along the +z-axis. Because of an electric field along the +y-axis, the charge particle does not change velocity. What is the sign of this particle?

The particle could be either positive or negative.

An object is hung using a metal spring. If now a current is passed through the spring, what will happen to this system?

The spring will contract, raising the weight.

Which one of the following statements is correct? A) When a current-carrying wire is in your left hand, with your thumb in the direction of the current, your fingers point in the direction of the magnetic field lines. B) When a current-carrying wire is in your right hand, with your thumb in the direction of the current, your fingers point in the direction of the magnetic field lines. C) When a current-carrying wire is in your right hand, with your thumb in the direction of the current, your fingers point opposite to the direction of the magnetic field lines.

When a current-carrying wire is in your right hand, with your thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.

If a calculated quantity has units of (N · s)/(C · m), that quantity could be

a magnetic field.

If a calculated quantity has units of (N)/(A · m) , that quantity could be

a magnetic field.

When the switch is closed in the circuit shown in the figure, the wire between the poles of the horseshoe magnet deflects upward. From this you can conclude that the left end of the magnet is (Figure at Q37)

a south magnetic pole.

A charged particle moving along the +x-axis enters a uniform magnetic field pointing along the +z-axis. A uniform electric field is also present. Due to the combined effect of both fields, the particle does not change its velocity. What is the direction of the electric field?

along the +y-axis

An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, then the magnetic field must have a component

along the -z-axis

Consider an ideal solenoid of lengthL, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the length of the solenoid becomes twice as long (to 2L), but all other quantities remained the same, the magnetic field inside the solenoid will

become one-half as strong as initially.

A negatively-charged particle moves across a constant uniform magnetic field that is perpendicular to the velocity of the particle. The magnetic force on this particle

causes the particle to accelerate.

A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current

circles the wire in a counter-clockwise direction.

A straight bar magnet is initially 4 cm long, with the north pole on the right and the south pole on the left. If you cut the magnet in half, the right half will

contain a north pole on the right and a south pole on the left.

A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire as you view it in such a way that the current is coming directly toward you?

counterclockwise, around the y-axis

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? (Figure from Q60)

directly toward the bottom of the page

When you double the number of windings in an ideal solenoid while keeping all other parameters (radius, length and current) fixed, the magnetic field at the center of the solenoid will

double.

For the horseshoe magnet shown in the figure, the left end is a north magnetic pole and the right end is a south magnetic pole. When the switch is closed in the circuit, which way will the wire between the poles of the horseshoe magnet initially deflect? (Figure from Q38)

downward

In a certain velocity selector consisting of perpendicular electric and magnetic fields, the charged particles move toward the east, and the magnetic field is directed to the north. What direction should the electric field point?

downward

If you were to cut a small permanent bar magnet in half,

each piece would in itself be a smaller bar magnet with both north and south poles.

We observe that a moving charged particle experiences no magnetic force. From this we can definitely conclude that

either no magnetic field exists or the particle is moving parallel to the field.

In a velocity selector consisting of perpendicular electric and magnetic fields, the speeds of the charged particles passing through the selector are increased or decreased until they are equal to the desired speed.

false

A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field lines. Ignoring the particleʹs weight, the particle will

follow a circular path.

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

horizontally towards the east

A charged particle moves with a constant speed through a region where a uniform magnetic field is present. If the magnetic field points straight upward, the magnetic force acting on this particle will be strongest when the particle moves

in a plane parallel to Earthʹs surface.

A positive charge is moving to the right and experiences an upward magnetic force, as shown in the figure (from Q4). In which direction must the magnetic field have a component?

into the page

Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at a point exactly between the two wires

is zero.

When a ferromagnetic material is placed in an external magnetic field, the net magnetic field of its magnetic domains becomes

larger.

A charged particle that is moving in a static uniform magnetic field

may experience a magnetic force, but its speed will not change.

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?

out of the plane of the page

An electron is moving to the right, as shown in the figure. Suddenly it encounters uniform magnetic field pointing out of the page. Which one of the three paths shown will it follow in the field? (Figure from Q12)

path A

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 currentI flowing through this coil in the direction shown, what is the direction of the force acting on section AB of this coil? (Figure from Q33)

perpendicular to and into the page

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 currentI flowing through this coil in the direction shown, what is the direction of the force acting on section CD of this coil? (Figure from question Q34)

perpendicular to and out of the page

The direction of the force on a current-carrying wire in a magnetic field is

perpendicular to both the current and the magnetic field.

Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current directly toward you, and the wire on your left carries current directly away from you. From your point of view, the magnetic field at a point exactly midway between the two wires

points downward.

Consider an ideal solenoid of lengthL, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the radius of the solenoid is doubled to 2b, but all the other quantities remain the same, the magnetic field inside the solenoid will

remain the same.

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

south.

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

the current is perpendicular to the magnetic field lines.

A flat circular wire loop lies in a horizontal plane on a table and carries current in a counterclockwise direction when viewed from above. At this point, the earthʹs magnetic field points to the north and dips below the horizontal. Which side of the coil tends to lift off of the table due to the magnetic torque on the loop?

the south side

Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in the same direction,

the wires pull toward each other.

Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in opposite directions,

the wires push away from each other.

A proton has an initial velocity to the south but is observed to curve upward as the result of a magnetic field. This magnetic field must have a component

to the east.

An electron has an initial velocity to the south but is observed to curve upward as the result of a magnetic field. This magnetic field must have a component

to the west.

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

toward the north

At a particular instant, a proton moves toward the east in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it is

toward the north.

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?

toward the south

At a particular instant, an electron moves toward the east in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it is

toward the south.

After landing on an unexplored Klingon planet, Spock tests for the direction of the magnetic field by firing a beam of electrons in various directions and by recording the following observations: Electrons moving upward feel a magnetic force in the northwest direction. Electrons moving horizontally toward the north are pushed downward. Electrons moving horizontally toward the southeast are pushed upward. Mr. Spock therefore concludes that the magnetic field at this landing site is in which direction?

toward the southwest

A vertical wire carries a current straight up in a region where the magnetic field vector points toward the north. What is the direction of the magnetic force on this wire?

toward the west

A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward We may conclude that the magnetic field must have a component

towards the east.

An electron, moving west, enters a magnetic field. Because of this field the electron curves upward. We may conclude that the magnetic field must have a component

towards the north.

A proton, moving east, enters a magnetic field. Because of this magnetic field the proton curves downward. We may conclude that the magnetic field must have a component

towards the south.

A proton, moving west, enters a magnetic field. Because of this magnetic field the proton curves upward. We may conclude that the magnetic field must have a component

towards the south.

An electron, moving south, enters a magnetic field. Because of this field, the electron curves upward. We may conclude that the magnetic field must have a component

towards the west.

A negatively charged particle -Q is moving to the right, directly above a wire having a current I flowing to the right, as shown in the figure. In what direction is the magnetic force exerted on the particle due to the current? (Figure from Q59)

upward

A ring with a clockwise current (as viewed from above the ring) is situated with its center directly above another ring, which has a counter-clockwise current, as shown in the figure. In what direction is the net magnetic force exerted on the top ring due to the bottom ring? (Figure from Q48)

upward

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

westward

A 2.0-m straight wire carrying a current of 0.60 A is oriented parallel to a uniform magnetic field of 0.50 T. What is the magnitude of the magnetic force on it?

zero

If a calculated quantity has units of T · m/A, that quantity could be

μ0.