Chapter #28 Solutions - University Physics with Modern Physics Volume 2 (Chapters 21-40) - Gary Westfall, Wolfgang Bauer - 2nd Edition

1cc. A wire is carrying a current, iin, into the page as shown in the figure. In which direction does the magnetic field point at points P and Q?...a) to the right at P and upward (toward the top of the page) at Qb) upward at P and to the right at Qc) downward at P and to the right at Qd) upward at P and to the left at Q Get solution

1mcq. Two long, straight wires are parallel to each other. The wires carry currents of different magnitudes. If the amount of current flowing in each wire is doubled, the magnitude of the force between the wires will bea) twice the magnitude of the original force.b) four times the magnitude of the original force.c) the same as the magnitude of the original force.d) half of the magnitude of the original force. Get solution

2cc. Wire 1 has a current flowing out of the page, iout, as shown in the figure. Wire 2 has a current flowing into the page, iin. What is the direction of the magnetic field at point P?...a) upward in the plane of the pageb) to the rightc) downward in the plane of the paged) to the lefte) The magnetic field at point P is zero. Get solution

2mcq. A current element produces a magnetic field in the region surrounding it. At any point in space, the magnetic field produced by this current element points in a direction that isa) radial from the current element to the point in space.b) parallel to the current element.c) perpendicular to the current element and to the radial direction. Get solution

3cc. In Figure 28.2, compass needles show the magnetic field around a currentcarrying wire. In the figure, the northpointing end of the compass needle corresponds toa) the red end.b) the gray end.c) either the red end or the gray end, depending on how the compass is moved toward the wire.d) The end cannot be identified from the information contained in the figure.Figure 28.2 Wire (yellow circle) with current running through it: (a) into the page (indicated by the cross); (b) out of the page (indicated by the dot). The orientation of a compass needle placed close to the wire is shown at different locations around the wire.a) ...b) ... Get solution

3mcq. The number of turns in a solenoid is doubled, and its length is halved. How does its magnetic field change?a) It doubles.b) It is halved.c) It quadruples.d) It remains unchanged. Get solution

4cc. Two parallel wires are near each other, as shown in the figure. Wire 1 carries a current i, and wire 2 carries a current 2i. Which statement about the magnetic forces that the two wires exert on each other is correct?...a) The two wires exert no forces on each other.b) The two wires exert attractive forces of the same magnitude on each other.c) The two wires exert repulsive forces of the same magnitude on each other.d) Wire 1 exerts a stronger force on wire 2 than wire 2 exerts on wire 1.e) Wire 2 exerts a stronger force on wire 1 than wire 1 exerts on wire 2. Get solution

4mcq. Consider two parallel current-carrying wires. The magnetic fields cause attractive forces between the wires, so it appears that the magnetic field due to one wire is doing work on the other wire. How is this explained?a) The magnetic force can do no work on isolated charges; this says nothing about the work it can do on charges confined in a conductor.b) Since only an electric field can do work on charges, it is actually the electric fields doing the work here.c) This apparent work is due to another type of force. Get solution

5cc. A wire is carrying a current, i, in the positive y-direction, as shown in the figure. The wire is located in a uniform magnetic field, ... oriented in such a way that the magnetic force on the wire is maximized. The magnetic force acting on the wire, ... is in the negative x-direction. What is the direction of the magnetic field?...a) the positive x-directionb) the negative x-directionc) the negative y-directiond) the positive z-directione) the negative z-direction Get solution

5mcq. In a solenoid in which the wires are wound such that each loop touches the adjacent ones, which of the following will increase the magnetic field inside the magnet?a) making the radius of the loops smallerb) increasing the radius of the wirec) increasing the radius of the solenoidd) decreasing the radius of the wiree) immersing the solenoid in gasoline Get solution

6cc. Two identical wire loops carry the same current, i, as shown in the figure. What is the direction of the magnetic field at point P?...a) upward (toward the top of the page)b) toward the rightc) downwardd) toward the lefte) The magnetic field at point P is zero. Get solution

6mcq. Two insulated wires cross at a 90° angle. Currents are sent through the two wires. Which one of the figures best represents the configuration of the wires if the current in the horizontal wire flows in the positive x-direction and the current in the vertical wire flows in the positive y-direction?(a) ...(b) ...(c) ...(d) ... Get solution

7cc. Three wires are carrying currents of the same magnitude, i, in the directions shown in the figure. Four Amperian loops (a), (b), (c), and (d) are shown. For which Amperian loop is the magnitude of ... the greatest?...a) loop ab) loop bc) loop cd) loop de) All four loops yield the same value of ... Get solution

7mcq. What is a good rule of thumb for designing a simple magnetic coil? Specifically, given a circular coil of radius ~1 cm, what is the approximate magnitude of the magnetic field, in gausses per amp per turn? (Note: 1 G = 0.0001 T.)a) 0.0001 G/(A-turn)b) 0.01 G/(A-turn)c) 1 G/(A-turn)d) 100 G/(A-turn) Get solution

8cc. You have a solenoid with a fixed number of turns connected to a power supply that can supply a fixed amount of current. To double the field inside the solenoid, you cana) double the radius of the solenoid.b) halve the radius of the solenoid.c) double the length of the solenoid.d) halve the length of the solenoid. Get solution

8mcq. A solid cylinder carries a current that is uniform over its cross section. Where is the magnitude of the magnetic field the greatest?a) at the center of the cylinder’s cross sectionb) in the middle of the cylinderc) at the surfaced) none of the above Get solution

9mcq. Two long, straight wires have currents flowing in them in the same direction, as shown in the figure. The force between the wires is...a) attractive.b) repulsive.c) zero. Get solution

10mcq. In a magneto-optic experiment, a liquid sample in a 10-mL spherical vial is placed in a highly uniform magnetic field, and a laser beam is directed through the sample. Which of the following should be used to create the uniform magnetic field required by the experiment?a) a 5-cm-diameter flat coil consisting of one turn of 4-gauge wireb) a 10-cm-diameter, 20-turn, single-layer, tightly wound coil made of 18-gauge wirec) a 2-cm-diameter, 10-cm-long, tightly wound solenoid made of 18-gauge wired) a set of two coaxial 10-cm-diameter coils at a distance of 5 cm apart, each consisting of one turn of 4-gauge wire Get solution

11mcq. Assume that a lightning bolt can be modeled as a long, straight line of current. If 15.0 C of charge passes by a point in 1.50 · 10–3 s, what is the magnitude of the magnetic field at a distance of 26.0 m from the lightning bolt?a) 7.69 · 10–5 Tb) 9.22 · 10–3 Tc) 4.21 · 10–2 Td) 1.11 · 10–1 Te) 2.22 · 102 T Get solution

12mcq. Two solenoids have the same length, but solenoid 1 has 15 times more turns and 1/9 as large a radius and carries 7 times as much current as solenoid 2. Calculate the ratio of the magnitude of the magnetic field inside solenoid 1 to that of the magnetic field inside solenoid 2.a) 105b) 123c) 144d) 168e) 197 Get solution

13mcq. The wire in the figure carries a current i and contains a circular arc of radius R and angle π/2 and two straight sections that are mutually perpendicular and, if extended, would intersect the center, C, of the arc. What is the magnetic field at point C due to the wire?...a) ...b) ...c) ...d) ...e) ... Get solution

14mcq. Wire 1 carries a current i1, and wire 2 carries a current i2 in the opposite direction, as shown in the figure. What is the direction of the force exerted by wire 1 on a length L of wire 2?a) toward wire 1b) away from wire 1c) Wire 1 does not exert a force on wire 2 in this situation.... Get solution

15cq. Many electrical applications use twisted-pair cables in which the ground and signal wires spiral about each other. Why? Get solution

16cq. Discuss how the accuracy of a compass needle in showing the true direction of north can be affected by the magnetic field due to currents in wires and appliances in a residential building. Get solution

17cq. Can an ideal solenoid, one with no magnetic field outside the solenoid, exist? If not, does that invalidate the derivation of the magnetic field inside the solenoid (Section 28.4)? Get solution

18cq. Conservative forces tend to act on objects in such a way as to minimize a system’s potential energy. Use this principle to explain the direction of the force on the current-carrying loop described in Example 28.1.Example 28.1 Force on a Loop......... Get solution

19cq. Two particles, each with charge q and mass m, are traveling in a vacuum on parallel trajectories a distance d apart and at a speed v (much less than the speed of light). Calculate the ratio of the magnitude of the magnetic force that each exerts on the other to the magnitude of the electric force that each exerts on the other: Fm/Fe. Get solution

20cq. A long, straight, cylindrical tube of inner radius a and outer radius b carries a total current i uniformly across its cross section. Determine the magnitude of the magnetic field due to the tube at the midpoint between the inner and outer radii. Get solution

21cq. Three identical straight wires are connected in a T, as shown in the figure. If current i flows into the junction, what is the magnetic field at point P, a distance d from the junction?... Get solution

22cq. In a certain region, there is a constant and uniform magnetic field, ... Any electric field in the region is also unchanging in time. Find the current density, ... in this region. Get solution

23cq. The magnetic character of bulk matter is determined largely by electron spin magnetic moments, rather than by orbital dipole moments. (Nuclear contributions are negligible, as the proton’s spin magnetic moment is about 658 times smaller than that of the electron.) If the atoms or molecules of a substance have unpaired electron spins, the associated magnetic moments give rise to paramagnetism or to ferromagnetism if the interactions between atoms or molecules are strong enough to align them in domains. If the atoms or molecules have no net unpaired spins, then magnetic perturbations of electrons’ orbits give rise to diamagnetism.a) Molecular hydrogen gas (H2) is weakly diamagnetic. What does this imply about the spins of the two electrons in the hydrogen molecule?b) What would you expect the magnetic behavior of atomic hydrogen gas (H) to be? Get solution

24cq. Exposed to sufficiently high magnetic fields, materials saturate, or approach a maximum magnetization. Would you expect the saturation (maximum) magnetization of paramagnetic materials to be much less than, roughly the same as, or much greater than that of ferromagnetic materials? Explain why. Get solution

25cq. A long, straight wire carries a current, as shown in the figure. A single electron is shot directly toward the wire from above. The trajectory of the electron and the wire are in the same plane. Will the electron be deflected from its initial path, and if so, in which direction?... Get solution

26cq. A square loop, with sides of length L, carries current i. Find the magnitude of the magnetic field from the loop at the center of the loop, as a function of i and L. Get solution

27cq. A current of constant density, J0, flows through a very long cylindrical conducting shell with inner radius a and outer radius b. What is the magnetic field in the regions r a, a r b, and r > b? Does Barb = Br>b for r = b? Get solution

28cq. Parallel wires, a distance D apart, carry a current, i, in opposite directions as shown in the figure. A circular loop, of radius R = D/2, has the same current flowing in a counterclockwise direction. Determine the magnitude and the direction of the magnetic field from the loop and the parallel wires at the center of the loop, as a function of i and R.... Get solution

29cq. The current density in a cylindrical conductor of radius R varies as J(r) = J0e–r/R (in the region from zero to R). Express the magnitude of the magnetic field in the regions r R and r > R. Produce a sketch of the radial dependence, B(r). Get solution

30. Two long parallel wires are separated by 3.0 mm. The current flowing in one of the wires is twice that in the other wire. If the magnitude of the force on a 1.0-m length of one of the wires is 7.0 µN, what are the magnitudes of the two currents? Get solution

31. An electron is shot from an electron gun with a speed of 4.0 · 105 m/s and moves parallel to and at a distance of 5.0 cm above a long, straight wire carrying a current of 15 A. Determine the magnitude and the direction of the acceleration of the electron the instant it leaves the electron gun. Get solution

32. An electron moves in a straight line at a speed of 5.00 · 106 m/s. What are the magnitude and the direction of the magnetic field created by the moving electron at a distance d = 5.00 m ahead of it on its line of motion? How does the answer change if the moving particle is a proton? Get solution

33. Suppose that the magnetic field of the Earth were due to a single current moving in a circle of radius 2.00 · 103 km through the Earth’s molten core. The strength of the Earth’s magnetic field on the surface near a magnetic pole is about 6.00 · 10–5 T. About how large a current would be required to produce such a field? Get solution

34. A square ammeter has sides of length 3.00 cm. The sides of the ammeter are capable of measuring the magnetic field they are subject to. When the ammeter is clamped around a wire carrying a direct current, as shown in the figure, the average value of the magnetic field measured in the sides is 3.00 G. What is the current in the wire?... Get solution

35. A long, straight wire carrying a 2.00-A current lies along the x-axis. A particle with charge q = –3.00 µC moves parallel to the y-axis through the point (x,y,z) = (0,2,0). Where in the xy-plane should another long, straight wire be placed so that there is no magnetic force on the particle at the point where it crosses the plane? Get solution

36. Find the magnetic field in the center of a wire semicircle like that shown in the figure, with radius R = 10.0 cm, if the current in the wire is i = 12.0 A.... Get solution

37. Two very long wires run parallel to the z-axis, as shown in the figure. They each carry a current, i1 = i2 = 25.0 A, flowing in the direction of the positive z-axis. The magnetic field of the Earth is given by ... = (2.60 · 10–5)ŷ T (in the xy-plane and pointing due north). A magnetic compass needle is placed at the origin. Determine the angle θ between the compass needle and the x-axis. (Hint: The compass needle will align its axis along the direction of the net magnetic field.)... Get solution

38. Two identical coaxial coils of wire of radius 20.0 cm are directly on top of each other, separated by a 2.00-mm gap. The lower coil is on a flat table and has a current i in the clockwise direction; the upper coil carries an identical current and has a mass of 0.0500 kg. Determine the magnitude and the direction that the current in the upper coil has to have to keep it levitated at the distance 2.00 mm above the lower coil. Get solution

39. A long, straight wire lying along the x-axis carries a current, i, flowing in the positive x-direction. A second long, straight wire lies along the y-axis and has a current i in the positive y-direction. What are the magnitude and the direction of the magnetic field at point z = b on the z-axis? Get solution

40. A square loop of wire with a side length of 10.0 cm carries a current of 0.300 A. What is the magnetic field in the center of the square loop? Get solution

41. The figure shows the cross section through three long wires with a linear mass distribution of 100. g/m. They carry currents i1, i2, and i3 in the directions shown. Wires 2 and 3 are 10.0 cm apart and are attached to a vertical surface, and each carries a current of 600. A. What current, i1, will allow wire 1 to “float” at a perpendicular distance d = 10.0 cm from the vertical surface? (Neglect the thickness of the wires.)... Get solution

42. A hairpin configuration is formed of two semi-infinite straight wires that are 2.00 cm apart and joined by a semicircular piece of wire (whose radius must be 1.00 cm and whose center is at the origin of xyz-coordinates). The top wire lies along the line y = 1.00 cm, and the bottom wire lies along the line y = –1.00 cm; these two wires are in the left side (x xy-plane. The current in the hairpin is 3.00 A, and it is directed toward the right in the top wire, clockwise around the semicircle, and to the left in the bottom wire. Find the magnetic field at the origin of the coordinate system. Get solution

43. A long, straight wire is located along the x-axis (y = 0 and z = 0). The wire carries a current of 7.00 A in the positive x-direction. What are the magnitude and the direction of the force on a particle with a charge of 9.00 C located at (+1.00 m,+2.00 m,0), when it has a velocity of 3000. m/s in each of the following directions?a) the positive x-directionb) the positive y-directionc) the negative z-direction Get solution

44. A long, straight wire has a 10.0-A current flowing in the positive x-direction, as shown in the figure. Close to the wire is a square loop of copper wire that carries a 2.00-A current in the direction shown. The near side of the loop is d = 0.500 m away from the wire. The length of each side of the square is a = 1.00 m.a) Find the net force between the two current-carrying objects.b) Find the net torque on the loop.... Get solution

45. A square box with sides of length 1.00 m has one corner at the origin of a coordinate system, as shown in the figure. Two coils are attached to the outside of the box. One coil is on the box face that is in the xz-plane at y = 0, and the second is on the box face in the yz-plane at x = 1.00 m. Each of the coils has a diameter of 1.00 m and contains 30.0 turns of wire carrying a current of 5.00 A in each turn. The current in each coil is clockwise when the coil is viewed from outside the box. What are the magnitude and the direction of the magnetic field at the center of the box?... Get solution

46. The current density in a cylindrical conductor of radius R varies as J(r) = J0r/R (in the region from zero to R). Express the magnitude of the magnetic field in the regions r R and r > R. Produce a sketch of the radial dependence, B(r). Get solution

47. The figure shows a cross section across the diameter of a long, solid, cylindrical conductor. The radius of the cylinder is R = 10.0 cm. A current of 1.35 A is uniformly distributed throughout the conductor and is flowing out of the page. Calculate the direction and the magnitude of the magnetic field at positions ra = 0.0 cm, rb = 4.00 cm, rc = 10.0 cm, and rd = 16.0 cm.... Get solution

48. A coaxial wire consists of a copper core of radius 1.00 mm surrounded by a copper sheath of inside radius 1.50 mm and outside radius 2.00 mm. A current, i, flows in one direction in the core and in the opposite direction in the sheath. Graph the magnitude of the magnetic field as a function of the distance from the center of the wire. Get solution

49. A very large sheet of conducting material located in the xy-plane, as shown in the figure, has a uniform current flowing in the y-direction. The current density is 1.5 A/cm. Use Ampere’s Law to calculate the direction and the magnitude of the magnetic field just above the center of the sheet (not close to any edges).... Get solution

50. A current of 2.00 A is flowing through a 1000-turn solenoid of length L = 40.0 cm. What is the magnitude of the magnetic field inside the solenoid? Get solution

51. Solenoid A has twice the diameter, three times the length, and four times the number of turns of solenoid B. The two solenoids have currents of equal magnitudes flowing through them. Find the ratio of the magnitude of the magnetic field in the interior of solenoid A to that of solenoid B. Get solution

52. A long solenoid (diameter of 6.00 cm) is wound with 1000 turns per meter of thin wire through which a current of 0.250 A is maintained. A wire carrying a current of 10.0 A is inserted along the axis of the solenoid. What is the magnitude of the magnetic field at a point 1.00 cm from the axis? Get solution

53. A long, straight wire carries a current of 2.5 A.a) What is the strength of the magnetic field at a distance of 3.9 cm from the wire?b) If the wire still carries 2.5 A, but is used to form a long solenoid with 32 turns per centimeter and a radius of 3.9 cm, what is the strength of the magnetic field inside the solenoid? Get solution

55. A particle detector utilizes a solenoid that has 550 turns of wire per centimeter. The wire carries a current of 22 A. A cylindrical detector that lies within the solenoid has an inner radius of 0.80 m. Electron and positron beams are directed into the solenoid parallel to its axis. What is the minimum momentum perpendicular to the solenoid axis that a particle can have if it is to be able to enter the detector? Get solution

54. Figure 28.20a shows a Helmholtz coil used to generate uniform magnetic fields. Suppose the Helmholtz coil consists of two sets of coaxial wire loops with 15 turns of radius R = 75.0 cm, which are separated by R, and each coil carries a current of 0.123 A flowing in the same direction. Calculate the magnitude and the direction of the magnetic field in the center between the coils.Figure 28.20 (a) A typical Helmholtz coil used in physics labs generates a nearly uniform magnetic field in its interior.... Get solution

56. An electron has a spin magnetic moment of magnitude µ = 9.285 · 10–24A m2. Consequently, it has energy associated with its orientation in a magnetic field. If the difference between the energy of an electron that is “spin up” in a magnetic field of magnitude B and the energy of one that is “spin down” in the same magnetic field (where “up” and “down” refer to the direction of the magnetic field) is 9.460 · 10–25 J, what is the field magnitude, B? Get solution

57. When a magnetic dipole is placed in a magnetic field, it has a natural tendency to minimize its potential energy by aligning itself with the field. If there is sufficient thermal energy present, however, the dipole may rotate so that it is no longer aligned with the field. Using kBT as a measure of the thermal energy, where kB is Boltzmann’s constant and T is the temperature in kelvins, determine the temperature at which there is sufficient thermal energy to rotate the magnetic dipole associated with a hydrogen atom from an orientation parallel to an applied magnetic field to one that is antiparallel to the applied field. Assume that the strength of the field is 0.15 T. Get solution

58. Aluminum becomes superconducting at a temperature around 1.0 K if exposed to a magnetic field of magnitude less than 0.0105 T. Determine the maximum current that can flow in an aluminum superconducting wire with radius R = 1.0 mm. Get solution

59. If you want to construct an electromagnet by running a current of 3.00 A through a solenoid with 500. windings and length 3.50 cm and you want the magnetic field inside the solenoid to have the magnitude B = 2.96 T, you can insert a ferrite core into the solenoid. What value of the relative magnetic permeability should this ferrite core have in order to make this work? Get solution

60. What is the magnitude of the magnetic field inside a long, straight tungsten wire of circular cross section with diameter 2.4 mm and carrying a current of 3.5 A, at a distance of 0.60 mm from its central axis? Get solution

61. You charge up a small rubber ball of mass 200. g by rubbing it over your hair. The ball acquires a charge of 2.00 µC. You then tie a 1.00-m-long string to it and swing it in a horizontal circle, providing a centripetal force of 25.0 N. What is the magnetic moment of the system? Get solution

62. Consider a model of the hydrogen atom in which an electron orbits a proton in the plane perpendicular to the proton’s spin angular momentum (and magnetic dipole moment) at a distance equal to the Bohr radius, a0 = 5.292 · 10–11 m. (This is an oversimplified classical model.) The spin of the electron is allowed to be either parallel to the proton’s spin or antiparallel to it; the orbit is the same in either case. But since the proton produces a magnetic field at the electron’s location, and the electron has its own intrinsic magnetic dipole moment, the energy of the electron differs depending on its spin. The magnetic field produced by the proton’s spin may be modeled as a dipole field, like the electric field due to an electric dipole discussed in Chapter 22. Calculate the energy difference between the two electron-spin configurations. Consider only the interaction between the magnetic dipole moment associated with the electron’s spin and the field produced by the proton’s spin. Get solution

63. Consider an electron to be a uniformly dense sphere of charge, with a total charge of –e = –1.602 · 10–19 C, spinning at an angular frequency, ω.a) Write an expression for its classical angular momentum of rotation, L.b) Write an expression for its magnetic dipole moment, µ.c) Find the ratio, γe = µ/L, known as the gyromagnetic ratio. Get solution

64. Two 50-turn coils, each with a diameter of 4.00 m, are placed 1.00 m apart, as shown in the figure. A current of 7.00 A is flowing in the wires of both coils; the direction of the current is clockwise for both coils when viewed from the left. What is the magnitude of the magnetic field in the center between the two coils?... Get solution

66. You are standing at a spot where the magnetic field of the Earth is horizontal, points due northward, and has magnitude 40.0 µT. Directly above your head, at a height of 12.0 m, a long, horizontal cable carries a steady direct current of 500. A due northward. Calculate the angle θ by which your magnetic compass needle is deflected from true magnetic north by the effect of the cable. Don’t forget the sign of θ —is the deflection eastward or westward? Get solution

65. The wires in the figure are separated by a vertical distance d. Point B is at the midpoint between the two wires; point A is a distance d/2 from the lower wire. The horizontal distance between A and B is much larger than d. Both wires carry the same current, i. The strength of the magnetic field at point A is 2.00 mT. What is the strength of the field at point B?... Get solution

67. The magnetic dipole moment of the Earth is approximately 8.0 · 1022 A m2. The source of the Earth’s magnetic field is not known; one possibility might be the circulation of ions in the Earth’s molten outer core. Assume that the circulating ions move a circular loop of radius 2500 km. What “current” must they produce to yield the observed field? Get solution

68. A circular wire loop has a radius R = 0.12 m and carries a current i = 0.10 A. The loop is placed in the xy-plane in a uniform magnetic field given by ... = –1.5ẑ T, as shown in the figure. Determine the direction and the magnitude of the loop’s magnetic moment and calculate the potential energy of the loop in the position shown. If the wire loop can move freely, how will it orient itself to minimize its potential energy, and what is the value of the lowest potential energy?... Get solution

70. In a coaxial cable, the solid core carries a current i. The sheath also carries a current i but in the opposite direction, and it has an inner radius a and an outer radius b. The current density is equally distributed over each conductor. Find an expression for the magnetic field at a distance a from the center of the core. Get solution

69. A 0.90-m-long solenoid has a radius of 5.0 mm. When the wire carries a 0.20-A current, the magnetic field inside the solenoid is 5.0 mT. How many turns of wire are there in the solenoid? Get solution

71. A 50-turn rectangular coil of wire with dimensions 10.0 cm by 20.0 cm lies in a horizontal plane, as shown in the figure. The axis of rotation of the coil is aligned north and south. It carries a current i = 1.00 A and is in a magnetic field pointing from west to east. A mass of 50.0 g hangs from one side of the coil. Determine the strength the magnetic field has to have to keep the coil in the horizontal orientation.... Get solution

72. Two long, straight parallel wires are separated by a distance of 20.0 cm. Each wire carries a current of 10.0 A in the same direction. What is the magnitude of the resulting magnetic field at a point that is 12.0 cm from each wire? Get solution

73. A particle with a mass of 1.00 mg and a charge q is moving at a speed of 1000. m/s along a horizontal path 10.0 cm below and parallel to a straight current-carrying wire. Determine q if the magnitude of the current in the wire is 10.0 A. Get solution

74. A conducting coil consisting of n turns of wire is placed in a uniform magnetic field given by ... = 2.00ŷ T, as shown in the figure. The radius of the coil is R = 5.00 cm, and the angle between the magnetic field vector and the unit normal vector to the coil is θ = 60.0°. The current through the coil is i = 5.00 A.a) Specify the direction of the current in the coil, given the direction of the magnetic dipole moment, ..., shown in the figure.b) Calculate the number of turns, n, the coil must have for the torque on the loop to be 3.40 N m.c) If the radius of the loop is decreased to R = 2.50 cm, what should the number of turns, N, be for the torque to remain unchanged? Assume that i, B, and θ stay the same.... Get solution

75. A loop of wire of radius R = 25.0 cm has a smaller loop of radius r = 0.900 cm at its center, with the planes of the two loops perpendicular to each other. When a current of 14.0 A is passed through both loops, the smaller loop experiences a torque due to the magnetic field produced by the larger loop. Determine this torque, assuming that the smaller loop is sufficiently small that the magnetic field due to the larger loop is the same across its entire surface. Get solution

76. Two wires, each 25.0 cm long, are connected to two separate 9.00-V batteries, as shown in the figure. The resistance of the first wire is 5.00 Ω, and that of the other wire is unknown (R). If the separation between the wires is 4.00 mm, what value of R will produce a force of magnitude 4.00 · 10–5 N between them? Is the force attractive or repulsive?... Get solution

77. A proton is moving under the combined influence of an electric field (E = 1000. V/m) and a magnetic field (B = 1.20 T), as shown in the figure.a) What is the acceleration of the proton at the instant it enters the crossed fields?b) What would the acceleration be if the direction of the proton’s motion were reversed?... Get solution

79. An electromagnetic doorbell has been constructed by wrapping 70 turns of wire around a long, thin rod, as shown in the figure. The rod has a mass of 30.0 g, a length of 8.00 cm, and a cross-sectional area of 0.200 cm2. The rod is free to pivot about an axis through its center, which is also the...center of the coil. Initially, the rod makes an angle of θ = 25.0° with the horizontal. When θ = 0.00°, the rod strikes a bell. A uniform magnetic field of 900. G is directed at an angle θ = 0.00°.a) If a current of 2.00 A is fl owing in the coil, what is the torque on the rod when θ = 25.0°?b) What is the angular velocity of the rod when it strikes the bell? Get solution

78. A toy airplane of mass 0.175 kg, with a charge of 36 mC, is flying with a speed of 2.8 m/s at a height of 17.2 cm above and parallel to a wire, which is carrying a 25-A current. The airplane experiences some acceleration. Determine this acceleration. Get solution

80. Two long, parallel wires separated by a distance d carry currents in opposite directions. If the left -hand wire carries a current i/2 and the righthand wire carries a current i, determine where the magnetic field is zero. Get solution

81. A horizontally oriented coil of wire of radius 5.00 cm that carries a current, i, is being levitated by the south pole of a vertically oriented bar magnet suspended above its center, as shown in the figure. If the magnetic field on all parts of the coil makes an angle θ = 45.0° with the vertical, determine the magnitude and the direction of the current needed to keep the coil floating in midair. The magnitude of the magnetic field is B = 0.0100 T, the number of turns in the coil is N = 10.0, and the total coil mass is 10.0 g.... Get solution

82. As shown in the figure, a long, hollow, conducting cylinder of inner radius a and outer radius b carries a current that is fl owing out of the page. Suppose that a = 5.00 cm, b = 7.00 cm, and the current i = 100. mA, uniformly distributed over the cylinder wall (between a and b). Find the magnitude of the magnetic field at each of the following distances r from the center of the cylinder:a) r = 4.00 cmb) r = 6.50 cmc) r = 9.00 cm... Get solution

83. A wire of radius R carries a current i. The current density is given by J = J0(1 – r/R), where r is measured from the center of the wire and J0 is a constant. Use Ampere’s Law to find the magnetic field inside the wire at a distance r R from the central axis. Get solution

84. A circular wire of radius 5.0 cm has a current of 3.0 A fl owing in it. The wire is placed in a uniform magnetic field of 5.0 mT.a) Determine the maximum torque on the wire.b) Determine the range of the magnetic potential energy of the wire. Get solution

85. The loop shown in the figure is carrying a current of 3.857 A, and the distance r = 1.411 m. What is the magnitude of the magnetic field at point P inside the loop?... Get solution

86. The loop shown in the figure is carrying a current of 3.961 A. The magnitude of the magnetic field at point P inside the loop is 7.213 · 10–7 T. What is the value of r? Get solution

87. In the current-carrying loop shown in the figure, the distance r = 2.329 m. The magnitude of the magnetic field at point P inside the loop is 5.937 · 10–7 T. What is the current in the loop? Get solution

89. A toroidal magnet has an inner radius of 1.121 m and an outer radius of 1.311 m. Th e magnetic field at a distance of 1.216 m from the center of the toroid is 78.30 mT. There are 22,381 turns of wire in the toroid. What is the current in the toroid? Get solution

88. A toroidal magnet has an inner radius of 1.895 m and an outer radius of 2.075 m. When the wire carries a 33.45-A current, the magnetic field at a distance of 1.985 m from the center of the toroid is 66.78 mT. How many turns of wire are there in the toroid? Get solution

90. A toroidal magnet has an inner radius of 1.351 m and an outer radius of 1.541 m. The wire carries a 49.13-A current, and there are 24,945 turns in the toroid. What is the magnetic field at a distance of 1.446 m from the center of the toroid? Get solution


Chapter #40 Solutions - University Physics with Modern Physics Volume 2 (Chapters 21-40) - Gary Westfall, Wolfgang Bauer - 2nd Edition

1cc. Which isotope X is needed to complete the reaction ...a) ...b) ...c) ...d) ...e) ... Get solution 1mcq. Radium-226 decays by e...