ame: Date: Electromagnetism 2 1. A magnetic force acts on an electric charge in a magnetic field when A. the charge is not moving. B. the charge moves in the direction of the magnetic field. C. the charge moves in the opposite direction to the magnetic field. D. the charge moves at right angles to the lines of the magnetic field. 2. The diagram below shows a charged particle about to enter a region of uniform magnetic field directed into the page. magnetic field charged particle Which of the following correctly describes the change, if any, in the kinetic energy and the momentum of the particle in the magnetic field? Kinetic energy Momentum A. Changed Changed B. Changed Unchanged C. Unchanged Changed D. Unchanged Unchanged 1
3. A straight conductor is in the plane of a uniform magnetic field as shown. current I magnetic field The current in the conductor is I and the conductor is at an angle θ to the magnetic field. The force per unit length on the conductor due to the current in the magnetic field is. Which is the correct expression for the magnitude of the magnetic field strength? A. B. C. D. sinθ I cosθ I I sinθ I cosθ 4. The diagram below shows three parallel wires, Q and R that are equally spaced. I I I wire wire Q wire R The currents in the wires are each of the same magnitude I and are in the directions shown. The resultant force on wire Q due to the current in wire and in wire R is A. perpendicular and into the plane of the paper. B. perpendicular and out of the plane of the paper. C. in the plane of the paper to the right. D. in the plane of the paper to the left. 2
5. A long, straight current-carrying wire is placed normal to the plane of the page. The current in the wire is into the plane of the page. Which of the following diagrams best represents the magnetic field around the wire? A. B. C. D. 6. The Earth s magnetic field may be compared with that of a bar magnet. Which of the following diagrams correctly shows the orientation of the bar magnet in this model? A. geographical north pole B. geographical north pole C. geographical north pole D. geographical north pole 3
7. This question is about magnetic fields. (a) Using the diagram below, draw the magnetic field pattern of the Earth. orth Earth (b) tate what other object produces a magnetic field pattern similar to that of the Earth.... (c) A long vertical wire passes through a sheet of cardboard that is held horizontal. A small compass is placed at the point and the needle points in the direction shown. cardboard sheet direction of compass needle A current is passed through the wire and the compass needle now points in a direction that makes an angle of 30 to its original direction as shown below. direction of compass needle with current in wire cardboard sheet 30 original direction of compass needle 4
(i) Draw an arrow on the wire to show the direction of current in the wire. Explain why it is in the direction that you have drawn. The magnetic field strength at point due to the current in the wire is B W and the strength of the horizontal component of the Earth s magnetic field is B E. Deduce, by drawing a suitable vector diagram, that B E = B W tan 60. (Total 7 marks) 8. This question is about forces on charged particles in electric and magnetic fields. The diagram shows two parallel plates situated in a vacuum. One plate is at a positive potential with respect to the other. + ath of positively charged particle A positively charged particle passes into the region between the plates. Initially, the particle is travelling parallel to the plates. (a) On the diagram, (i) draw lines to represent the electric field between the plates. (3) show the path of the charged particle as it passes between, and beyond, the plates. 5
(b) An electron is accelerated from rest in a vacuum through a potential difference of 750 V. (i) Determine the change in electric potential energy of the electron. Deduce that the final speed of the electron is 1.6 10 7 m s 1. The diagram below shows a cross-section through a current-carrying solenoid. The current is moving into the plane of the paper at the upper edge of the solenoid and out of the plane of the paper at the lower edge. There is a vacuum in the solenoid. Current into plane of paper Current out plane of paper (c) (i) ketch lines to represent the magnetic field inside and at each end of the solenoid. (4) A positively charged particle enters the solenoid along its axis. On the diagram, show the path of the particle in the solenoid. An electron is injected into a region of uniform magnetic field of flux density 4.0 mt. The velocity of the electron is 1.6 10 7 m s 1 at an angle of 35 to the magnetic field, as shown below. 7 1.6 10 m s 1 35 Direction of magnetic field 6
(d) (i) Determine the component of the velocity of the electron normal to the direction of the magnetic field. Describe, making calculations where appropriate, the motion of the electron due to this component of the velocity. (4) (iii) Determine the component of the velocity of the electron along the direction of the magnetic field. (iv) tate and explain the magnitude of the force on the electron due to this component of the velocity. (e) With reference to your answers in (d), describe the shape of the path of the electron in the magnetic field. You may draw a diagram if you wish....... (Total 25 marks) 7