# Chapter 26: The Magnetic Field Section 26-1: The Force Exerted by a Magnetic Field, and Concept Checks 26-1 and 26-2

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Chapter 26: The Magnetic Field Section 26-1: The Force Exerted by a Magnetic Field, and Concept Checks 26-1 and 26-2 Slide 2 The direction of any magnetic field is specified as the direction that the north pole of a compass needle points toward when the needle is aligned in the field. Suppose that the direction of the magnetic field were instead specified as the direction pointed toward by the south pole of a compass needle aligned in the field. Would the right-hand rule for force then give the direction of the magnetic force on the moving positive charge, or would a left-hand rule be required? A.The right-hand rule would still work. B.A left-hand rule would be required. Slide 3 The direction of any magnetic field is specified as the direction that the north pole of a compass needle points toward when the needle is aligned in the field. Suppose that the direction of the magnetic field were instead specified as the direction pointed toward by the south pole of a compass needle aligned in the field. Would the right-hand rule for force then give the direction of the magnetic force on the moving positive charge, or would a left-hand rule be required? A.The right-hand rule would still work. B.A left-hand rule would be required. Slide 4 The particle in the figure A.is positively charged. B.is negatively charged. C.could be negatively or positively charged. Slide 5 The particle in the figure A.is positively charged. B.is negatively charged. C.could be negatively or positively charged. Slide 6 The phenomenon of magnetism is best understood in terms of A.the existence of magnetic poles. B.the magnetic fields associated with the movement of charged particles. C.gravitational forces between nuclei and orbital electrons. D.electrical fluids. E.None of these is correct. Slide 7 The phenomenon of magnetism is best understood in terms of A.the existence of magnetic poles. B.the magnetic fields associated with the movement of charged particles. C.gravitational forces between nuclei and orbital electrons. D.electrical fluids. E.None of these is correct. Slide 8 The left diagram shows a positively charged particle is moving with velocity v in a magnetic field B. Using the arrows in the right diagram, what is the direction of the magnetic force on the particle? Slide 9 Slide 10 The left diagram shows a force F on a negatively charged particle moving a magnetic field B. Using the arrows in the right diagram, what is the direction of the velocity of the particle? Slide 11 Slide 12 If the magnetic field vector is directed toward the north and a positively charged particle is moving toward the east, what is the direction of the magnetic force on the particle? A.up B.west C.south D.down E.east Slide 13 If the magnetic field vector is directed toward the north and a positively charged particle is moving toward the east, what is the direction of the magnetic force on the particle? A.up B.west C.south D.down E.east Slide 14 A positively charged particle is moving northward in a magnetic field. The magnetic force on the particle is toward the northeast. What is the direction of the magnetic field? A.up B.northeast C.southwest D.down E.This situation cannot exist. Slide 15 A positively charged particle is moving northward in a magnetic field. The magnetic force on the particle is toward the northeast. What is the direction of the magnetic field? A.up B.northeast C.southwest D.down E.This situation cannot exist. Slide 16 The SI unit of magnetic field is the tesla (T). This is equivalent to A.N s/(C m) B.N C/(s m) C.N m/s 2 D.C/(A s) E.None of these is correct. Slide 17 The SI unit of magnetic field is the tesla (T). This is equivalent to A.N s/(C m) B.N C/(s m) C.N m/s 2 D.C/(A s) E.None of these is correct. Slide 18 The region of space around a moving proton contains A.a magnetic field only. B.an electric field only. C.both an electric and a magnetic field. D.neither an electric nor a magnetic field. Slide 19 The region of space around a moving proton contains A.a magnetic field only. B.an electric field only. C.both an electric and a magnetic field. D.neither an electric nor a magnetic field. Slide 20 The magnetic force on a charged particle A.depends on the sign of the charge on the particle. B.depends on the velocity of the particle. C.depends on the magnetic field at the particle's instantaneous position. D.is at right angles to both the velocity and the direction of the magnetic field. E.is described by all of these. Slide 21 The magnetic force on a charged particle A.depends on the sign of the charge on the particle. B.depends on the velocity of the particle. C.depends on the magnetic field at the particle's instantaneous position. D.is at right angles to both the velocity and the direction of the magnetic field. E.is described by all of these. Slide 22 An electron is traveling horizontally east in the magnetic field of the earth near the equator. The direction of the force on the electron is A.zero B.north C.south D.upward E.downward Slide 23 An electron is traveling horizontally east in the magnetic field of the earth near the equator. The direction of the force on the electron is A.zero B.north C.south D.upward E.downward Slide 24 A current I flows in a wire that is oriented as shown. Which of the vectors represent the magnetic field that results in a maximum force on the wire? Slide 25 Slide 26 A wire of length L carries a current I, going from West to East, in the presence of a magnetic field B pointing vertically up. The wire moves a distance d to the south. The work done by the magnetic force on the moving charges is A. +ILBd B. -ILBd C. +IL 2 B/d D. -IL 2 B/d E. zero Slide 27 A wire of length L carries a current I, going from West to East, in the presence of a magnetic field B pointing vertically up. The wire moves a distance d to the south. The work done by the magnetic force on the moving charges is A. +ILBd B. -ILBd C. +IL 2 B/d D. -IL 2 B/d E. zero Slide 28 Chapter 26: The Magnetic Field Section 26-2: Motion of a Point Charge in a Magnetic Field Slide 29 A particle with charge q and mass m is moving with speed v in the +x direction enters a magnetic field of strength B pointing in the +y direction. The work done by the magnetic force on the particle as it travels one semi-circle is A. mqvB B. mv 2 C. qvB D.zero E. mv/qB Slide 30 A particle with charge q and mass m is moving with speed v in the +x direction enters a magnetic field of strength B pointing in the +y direction. The work done by the magnetic force on the particle as it travels one semi-circle is A. mqvB B. mv 2 C. qvB D.zero E. mv/qB Slide 31 A positively charged particle moves with speed v in the positive x direction. A uniform magnetic field of magnitude B exists in the negative z direction. You want to balance the magnetic force with an electric field so that the particle will continue along a straight line. The electric field should be in the A.positive x direction. B.positive z direction. C.negative y direction. D.negative x direction. E.negative z direction. Slide 32 A positively charged particle moves with speed v in the positive x direction. A uniform magnetic field of magnitude B exists in the negative z direction. You want to balance the magnetic force with an electric field so that the particle will continue along a straight line. The electric field should be in the A.positive x direction. B.positive z direction. C.negative y direction. D.negative x direction. E.negative z direction. Slide 33 A 7 Li nucleus with a charge of +3e and a mass of 7 u and a proton with a charge of +e and a mass of 1 u are both moving in a plane perpendicular to a magnetic field. The two particles have the same momentum. The ratio of the radius of curvature of the path of the proton (R p ) to that of the 7 Li nucleus (R Li ) is A. R p /R Li = 3 B. R p /R Li = 1/3 C. R p /R Li = 1/7 D. R p /R Li = 3/7 E. None of these is correct. Slide 34 A 7 Li nucleus with a charge of +3e and a mass of 7 u and a proton with a charge of +e and a mass of 1 u are both moving in a plane perpendicular to a magnetic field. The two particles have the same momentum. The ratio of the radius of curvature of the path of the proton (R p ) to that of the 7 Li nucleus (R Li ) is A. R p /R Li = 3 B. R p /R Li = 1/3 C. R p /R Li = 1/7 D. R p /R Li = 3/7 E. None of these is correct. Slide 35 A doubly ionized oxygen atom 16 O ++ is moving in the same uniform magnetic field as an alpha particle. The velocities of both particles are at right angles to the magnetic field. The paths of the particles have the same radius of curvature. The ratio of the energy of the alpha particle to that of the 16 O 2+ ion is A.E /E O = 1/1 B.E /E O = 1/4 C.E /E O = 1/16 D.E /E O = 4/1 E.None of these is correct. Slide 36 A doubly ionized oxygen atom 16 O ++ is moving in the same uniform magnetic field as an alpha particle. The velocities of both particles are at right angles to the magnetic field. The paths of the particles have the same radius of curvature. The ratio of the energy of the alpha particle to that of the 16 O 2+ ion is A.E /E O = 1/1 B.E /E O = 1/4 C.E /E O = 1/16 D.E /E O = 4/1 E.None of these is correct. Slide 37 Electrons travel at an initial velocity v 0. They pass through a set of deflection plates, between which there exists an electric field which deflects them upwards toward point b. In which direction should a magnetic field be applied so that the electrons land undeflected at a? Slide 38 Slide 39 An electron moves with speed v in the positive x direction. A uniform magnetic field of magnitude B exists in the positive y direction. As the electron moves through this region, it is A.deflected in the positive y direction. B.deflected in the positive z direction. C.deflected in the negative y direction. D.deflected in the negative z direction. E.undeviated in its motion. Slide 40 An electron moves with speed

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