1. (a) On the diagram below, draw the magnetic field pattern around a long straight currentcarrying

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1 1. (a) On the diagram below, draw the magnetic field pattern around a long straight currentcarrying conductor. current-carrying wire The diagram below shows a coil consisting of two loops of wire. The coil is suspended vertically cm 6.0 cm Each loop has a diameter of 6.0 cm and the separation of the loops is 0.20 cm. The coil forms part of an electrical circuit so that a current may be passed through the coil. (b) State and explain why, when the current is switched on in the coil, the distance between the two loops changes. 1

2 When there is a current I in the coil, a mass of 0.10 g hung from the free end of the coil returns the separation of the loops to the original value of 0.20 cm. The circumference C of a circle of radius r is given by the expression C = 2πr. Calculate the current I in the coil. You may assume that each loop behaves as a long straight current-carrying wire. (5) (Total 11 marks) 2. This question is about force fields. (a) Electric fields and magnetic fields may be represented by lines of force. The diagram below shows some lines of force. A B 2

3 State whether the field strength at A and at B is constant, increasing or decreasing when measured in the direction from A towards B. at A:... at B:... Explain why field lines can never touch or cross. (b) A bubble chamber is an apparatus that is used to show the paths of particles. A highenergy particle enters the chamber and, at a point P, there is a reaction that gives rise to two charged particles. The tracks of the particles are shown below. P high-energy particle There is a uniform field of force acting normally to the plane of the paper. State, and explain, whether the field of force is electric or magnetic. The path of each of the two particles produced in the reaction is a spiral. One particle is spiralling clockwise, the other anti-clockwise. Suggest why they spiral in opposite directions. 3

4 (iii) Outline why each path is a spiral, rather than a circle. (Total 10 marks) 3. This question is about magnetic fields. (a) Using the diagram below, draw the magnetic field pattern of the Earth. North Earth 4

5 (b) State 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 P and the needle points in the direction shown. cardboard sheet P 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 P 30 original direction of compass needle 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 P 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. 5

6 Deduce, by drawing a suitable vector diagram, that B E = B W tan 60. (Total 7 marks) 4. This question is about motion of a charged particle in a magnetic field. A charged particle is projected from point X with speed v at right angles to a uniform magnetic field. The magnetic field is directed out of the plane of the page. The particle moves along a circle of radius R and centre C as shown in the diagram below. region of magnetic field out of plane of page Y v R C X charged particle (a) On the diagram above, draw arrows to represent the magnetic force on the particle at position X and at position Y. 6

7 (b) State and explain whether the charge is positive or negative; work is done by the magnetic force. v (c) A second identical charged particle is projected at position X with a speed in a 2 direction opposite to that of the first particle. On the diagram above, draw the path followed by this particle. (Total 6 marks) 5. 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. + Path of positively charged particle 7

8 A positively charged particle passes into the region between the plates. Initially, the particle is travelling parallel to the plates. (a) On the diagram, draw lines to represent the electric field between the plates. show the path of the charged particle as it passes between, and beyond, the plates. (b) An electron is accelerated from rest in a vacuum through a potential difference of 750 V. Determine the change in electric potential energy of the electron. Deduce that the final speed of the electron is 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 8

9 (c) Sketch 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 m s 1 at an angle of 35 to the magnetic field, as shown below m s 1 35 Direction of magnetic field (d) 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) 9

10 (iii) Determine the component of the velocity of the electron along the direction of the magnetic field. (iv) State 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) 6. This question is about forces on charged particles. (a) A charged particle is situated in a field of force. Deduce the nature of the force-field (magnetic, electric or gravitational) when the force on the particle is along the direction of the field regardless of its charge and velocity; is independent of the velocity of the particle but depends on its charge; 10

11 (iii) depends on the velocity of the particle and its charge. (5) (b) An electron is accelerated from rest in a vacuum through a potential difference of 2.1 kv. Deduce that the final speed of the electron is m s The electron in (b) then enters a region of uniform electric field between two conducting horizontal metal plates as shown below. +95 V Path of electron m s 1 P 2.2 cm 0 V 12 cm The electric field outside the region of the plates may be assumed to be zero. The potential difference between the plates is 95 V and their separation is 2.2 cm. As the electron enters the region of the electric field, it is travelling parallel to the plates. (c) On the diagram above, draw an arrow at P to show the direction of the force due to the electric field acting on the electron. 11

12 Calculate the force on the electron due to the electric field. (d) The plates in the diagram above are of length 12 cm. Determine the time of flight between the plates. the vertical distance moved by the electron during its passage between the plates. (e) Suggest why gravitational effects were not considered when calculating the deflection of the electron

13 (f) In a mass spectrometer, electric and magnetic fields are used to select charged particles of one particular speed. A uniform magnetic field is applied in the region between the plates, such that the electron passes between the plates without being deviated. For this magnetic field, state and explain its direction; determine its magnitude. (g) The electric and magnetic fields in (f) remain unchanged. Giving a brief explanation in each case, compare qualitatively the deflection of the electron in (f) with that of an electron travelling at a greater initial speed; a proton having the same speed; 13

14 (iii) an alpha particle (α-particle) having the same speed. (7) (Total 30 marks) 7. This question is about the force between current-carrying wires. Diagram 1 below shows two long, parallel vertical wires each carrying equal currents in the same direction. The wires pass through a horizontal sheet of card. Diagram 2 shows a plan view of the wires looking down onto the card. eye sheet of card diagram 1 diagram 2 (a) Draw on diagram 1 the direction of the force acting on each wire. Draw on diagram 2 the magnetic field pattern due to the currents in the wire. 14

15 (b) The card is removed and one of the two wires is free to move. Describe and explain the changes in the velocity and in acceleration of the moveable wire (Total 7 marks) 15

Magnetism 2. D. the charge moves at right angles to the lines of the magnetic field. (1)

Magnetism 2. D. the charge moves at right angles to the lines of the magnetic field. (1) Name: Date: Magnetism 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