1 1 The diagram shows the same bar magnets with a coil of wire between them. direction of rotation N handle S galvanometer A (a) The coil of wire is rotated in the direction shown in the diagram. On the diagram, draw an arrow to show the direction of the current in the coil. Explain your answer. ........................................................................................................................................... ........................................................................................................................................... [2] (b) Explain how rotating the coil in the diagram continuously causes the galvanometer needle to show an alternating current. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [4] [Total: 6] 2 A radio is connected to the mains supply using a step-down transformer (a) Draw a labelled diagram of the structure of a basic step-down transformer. [3] 2 (b) Explain the operation of a basic transformer. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [3] [Total: 6] 3 A laptop computer uses a transformer to change the voltage of the mains electricity supply. The input (primary) voltage is 120 V. The input (primary) coil has 2000 turns and the output (secondary) coil has 200 turns. Calculate the output (secondary) voltage from the transformer. output (secondary) voltage = ...................................................... V [3] [Total: 3] 4 A student uses two bar magnets to create a uniform magnetic field. He places a current carrying wire at right angles to the magnetic field, as shown in the diagram. There is a force on the current-carrying wire. 3 (a) The student wants to reverse the direction of the force on the wire. State one change that reverses the direction of the force on the wire. ........................................................................................................................................... [1] (b) The student increases the separation of the poles of the permanent magnets. State and explain how increasing the separation affects the force on the current-carrying wire. ........................................................................................................................................... ........................................................................................................................................... [2] [Total: 3] 5 The diagram shows a horizontal conducting wire XY between two opposite magnetic poles. Wire XY forms a circuit with an ammeter. 4 (a) Y wire N X S A The wire XY is moved and there is a deflection on the ammeter that indicates there is a current in the wire from X to Y. On the table below, tick one box to indicate the direction of the movement of the wire XY. Explain your answer. into page out of page to the left to the right to the bottom of the page to the top of the page explanation ....................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [3] (b) State what is observed on the ammeter when the wire XY is moved (i) in the opposite direction to part (a) ............................................................................... (ii) in the same direction as part (a) but at a greater speed ............................................. [2] [Total: 5] 6 A clamp and stand hold a soft-iron bar above a bench. A coil of wire is wrapped round the soft-iron bar. The coil of wire is part of an electric circuit. This circuit is used to operate a bell in a different circuit, as shown in the diagram. 5 (a) Switch S is closed. The soft-iron arm is attracted to the soft-iron bar. Explain why the bell operates when the switch S is opened. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [4] (b) The switch S is closed. The soft-iron arm is attracted to the soft-iron bar. The battery in the circuit containing the soft-iron bar becomes fully discharged. State and explain whether the bell operates. ........................................................................................................................................... ........................................................................................................................................... [1] [Total: 5] 7 An electron source produces a narrow beam of electrons that all travel at the same speed. The electron source is placed in a vacuum and the beam of electrons travels vertically downwards. The diagram shows the beam of electrons before it passes between the N-pole and the S-pole of a magnet. 6 (a) Describe what is meant by the direction of a magnetic field. State the direction of the magnetic field between the two poles in the diagram. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [1] (b) Describe and explain what happens to the beam of electrons in the magnetic field between the poles of the magnet in the diagram. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [3] [Total: 4] 8 The diagram represents a current in a wire. The current is into the plane of the paper. 7 (a) Draw the pattern of the magnetic field produced around the wire. Show clearly the direction of the magnetic field. [2] (b) The direction of the current in the wire is reversed. The magnitude of the current is unchanged. State the effect that reversing the current has on the magnetic field produced. ........................................................................................................................................... ........................................................................................................................................... [1] [Total: 3]
