a Draw the direction of the force experienced by the electron at points A and B. [1] Explain why the electron describes part of a circular path while in the region of the b magnetic field. [1] c The radius of curvature of the path of the electron in the magnetic field is 5.0 cm. Calculate the speed of the electron. [5] v d Explain how your answer to c would change if the electron described a circular path of radius 2.5 cm. [2] 7 A proton of kinetic energy 15 keV travelling at right-angles to a magnetic field describes a circle of radius of 5.0 cm. The mass of a proton is 1.7 × 10–27 kg. a Show that the speed of the proton is 1.7 × 106 m s–1. [3] For this proton, calculate the centripetal force provided by the magnetic field. [3] b c Determine the magnetic flux density of the magnetic field that keeps the proton moving in its circular orbit. [3] d How long does it take for the proton to complete one orbit? [2] Extension 8 The diagram shows a velocity-selector for charged ions. Ions of a particular speed emerge from the slit. The parallel plates have a separation of 2.4 cm and are connected to a 5.0 kV supply. A magnetic field is applied at right-angles to the electric field between the plates such that the positively charged ions emerge from the slit of the velocity-selector at a speed of 6.0 × 106 m s–1. Calculate the magnetic flux density of the magnetic field. [6] An electron describes a circular orbit in a plane perpendicular to a uniform magnetic field. 9 Show that the time taken by an electron to complete one orbit in the magnetic field is independent of its speed T and its radius, and is given by: = T where is the magnetic flux density of the magnetic field, is the charge on an electron B e and is the mass of an electron. [5] m Total: Score: %
a Draw the direction of the force experienced by the electron at points A and B. [1] b Explain why the electron describes part of a circular path while in the region of the magnetic field. [1] c The radius of curvature of the path of the electron in the magnetic field is 5.0 cm. Calculate the speed v of the electron. [5] d Explain how your answer to c would change if the electron described a circular path of radius 2.5 cm. [2] 7 A proton of kinetic energy 15 keV travelling at right-angles to a magnetic field describes a circle of radius of 5.0 cm. The mass of a proton is 1.7 × 10–27 kg. a Show that the speed of the proton is 1.7 × 106 m s–1. [3] b For this proton, calculate the centripetal force provided by the magnetic field. [3] c Determine the magnetic flux density of the magnetic field that keeps the proton moving in its circular orbit. [3] d How long does it take for the proton to complete one orbit? [2] Extension 8 The diagram shows a velocity-selector for charged ions. Ions of a particular speed emerge from the slit. The parallel plates have a separation of 2.4 cm and are connected to a 5.0 kV supply. A magnetic field is applied at right-angles to the electric field between the plates such that the positively charged ions emerge from the slit of the velocity-selector at a speed of 6.0 × 106 m s–1. Calculate the magnetic flux density of the magnetic field. [6] 9 An electron describes a circular orbit in a plane perpendicular to a uniform magnetic field. Show that the time T taken by an electron to complete one orbit in the magnetic field is independent of its speed and its radius, and is given by: T = where B is the magnetic flux density of the magnetic field, e is the charge on an electron and m is the mass of an electron. [5] Total: Score: %
a2_student_worksheets.docx