1. An electron passes the north pole of a bar magnet as shown below. What is the direction of the magnetic force on the electron? A. Into the page B. Out of the page C. To the left D. To the right 2. A long straight wire carries an electric current perpendicularly out of the paper. Which of the following represents the magnetic field pattern due to the current? IB Questionbank Physics 1
3. An electron travelling in the direction shown by the arrow X, enters a region of uniform magnetic field. It leaves the region of field in the direction shown by the arrow Y. The direction of the magnetic field is A. in the direction of X. B. into the plane of the paper. C. in the opposite direction to X. D. out of the plane of the paper. IB Questionbank Physics 2
4. A particle, of mass m and charge q, moves with velocity v perpendicularly to a magnetic field. The magnitude of the magnetic force acting on the particle at a particular point is F. Which of the following gives the magnitude of the magnetic field strength at that point? A. B. C. D. F q F m F F q 5. A current is established in a coil of wire in the direction shown. The direction of the magnetic field at point P is A. out of the plane of the paper. B. into the plane of the paper. C. to the left. D. to the right. IB Questionbank Physics 3
6. An electron enters the vacuum between two oppositely charged plates with velocity v. The electron is followed by an alpha particle moving with the same initial velocity as the electron. A uniform magnetic field is directed out of the plane of the paper. The electron s path is undeflected. The path of the alpha particle will be A. deflected out of the plane of the paper. B. undeflected. C. deflected upward. D. deflected downward. IB Questionbank Physics 4
7. A point mass carries a positive charge +Q and is at rest in a magnetic field. The field is in the direction shown. The magnetic force acting on the charge is A. from left to right in the plane of the page. B. from top to bottom in the plane of the page. C. into the plane of the page. D. zero. IB Questionbank Physics 5
8. A current carrying wire is in the same plane as a uniform magnetic field. The angle between the wire and the magnetic field is θ. The magnetic force on the current carrying wire is A. zero. B. into the plane of the paper. C. out of the plane of the paper. D. at an angle θ to the direction of the magnetic field. IB Questionbank Physics 6
9. In the diagram, a long current-carrying wire is normal to the plane of the paper. The current in the wire is directed into the plane of the paper. Which of the arrows gives the direction of the magnetic field at point P? A. W B. X C. Y D. Z IB Questionbank Physics 7
10. A positively charged particle enters the space between two charged conducting plates, with a constant velocity directed parallel to the plates, as shown. The top plate is positively charged and the bottom plate is negatively charged. There is a magnetic field in the shaded region PQRS. The particle continues to move in a horizontal straight line between the plates. Which of the following correctly describes the magnetic field direction? A. Into plane of paper B. Out of plane of paper C. Up D. Down IB Questionbank Physics 8
11. An electron is moving in air at right angles to a uniform magnetic field. The diagram below shows the path of the electron. The electron is slowing down. Which of the following correctly gives the direction of motion of the electron and the direction of the magnetic field? Direction of motion Direction of magnetic field A. clockwise into plane of paper B. clockwise out of plane of paper C. anti-clockwise into plane of paper D. anti-clockwise out of plane of paper 12. This question is about force fields. (a) Outline what is meant by a field of force.......... (2) IB Questionbank Physics 9
(b) Five particles A to E are each placed in a different type of field. Complete the table to identify the nature of the field in which each particle is situated. Particle Charge on particle Initial direction of motion of particle Direction of force on particle Type of field A uncharged stationary in direction of field... B negative along direction of field opposite to direction of field... C positive normal to direction of field normal to direction of field... D positive normal to direction of field in direction of field... E uncharged opposite to direction of field in direction of field... (5) (Total 7 marks) 13. This question is about motion in a magnetic field. An electron, that has been accelerated from rest by a potential difference of 250 V, enters a region of magnetic field of strength 0.12 T that is directed into the plane of the page. IB Questionbank Physics 10
(a) The electron s path while in the region of magnetic field is a quarter circle. Show that the (i) speed of the electron after acceleration is 9.4 10 6 m s 1. (2) (ii) radius of the path is 4.5 10 4 m. (2) (b) The diagram below shows the momentum of the electron as it enters and leaves the region of magnetic field. The magnitude of the initial momentum and of the final momentum is 8.6 10 24 N s. (i) On the diagram above, draw an arrow to indicate the vector representing the change in the momentum of the electron. (1) IB Questionbank Physics 11
(ii) Show that the magnitude of the change in the momentum of the electron is 1.2 10 23 Ns. (1) (iii) The time the electron spends in the region of magnetic field is 7.4 10 11 s. Estimate the magnitude of the average force on the electron. (1) (Total 7 marks) IB Questionbank Physics 12