PD32a HSC Physics motors and generators student name....................... Monday, 30 May 2016 number о number о 1 1 c 26 2 2 17 27 3 3 18 28 4 4 19 29 5 5 6 6 7 7 8 8 9 9 10 a 10 b 11 c 12 d 13 e 14 f 15 g 16 11 17 12 18 13 19 14 20 15 a 21 b 22
2 c 23 16 a 24 b 25 result out of 29 applied to the system
PD32a
4 Question 1 Who discovered the generation of an electric current by a magnet moving near a coil? 1 Faraday Hertz Oersted Tesla Question 2 Which of the following can be used to show the production of alternating current? 1 Moving a wire that is part of a closed circuit through a magnetic field at varying speeds. Moving a solenoid that is connected into a circuit up and down. Rotate a current-carrying coil between the poles of a pair of radial magnets. Move a magnet in and out of a solenoid which is part of a closed circuit. Question 3 The north pole of a magnet is moved into a coil of wire which is connected to an ammeter. Predict the effect on the current indicated on the ammeter of: (a) moving the magnet into the coil faster. 1 (b) moving the magnet out of the coil more slowly. 1 (c) moving a south pole into the magnet at the same speed. 1 (d) moving a south pole out of the coil at double the speed. 1 (e) halving the number of turns in the coil. 1 (f) moving two north poles into the coil at the same speed. 1 (g) moving two south poles out of the coil faster. 1 Question 4 Outline Faraday s experiments with coils and magnets and the observations he made. 6
5 Question 5 A magnet is continuously moved towards and away from a coil which is connected to an 1 ammeter. The magnet does not ever move inside the coil. What will be observed on the ammeter? An increasing current as the magnet moves closer and a decreasing current as the magnet moves away. A decreasing current as the magnet moves closer and an increasing current as the magnet moves away. An alternating current. No current because the magnet did not move inside the coil. Question 6 The diagrams show the directions of the induced currents formed by magnets moving towards 1 or away from identical coils. Which of the diagrams is correct? W and Y only. X and Z only. W, Y and X only. X, Y and Z only. Question 7 Recall the two statements with which Faraday summarised his observations on electromagnetic 2 induction. Question 8 Explain the idea of relative movement between a conductor and a magnetic field. 3
6 Question 9 In an experiment a student moved a magnet into, through and out of a coil as shown in the 1 diagram. Which graph best shows the emf generated in the coil? Question 10 (a) Describe the experiment you did to observe the generation of an electric current by 4 moving a magnet in a coil or by moving a coil near a magnet. (b) Recall four factors which influenced the generation of an electric current in a coil as 2 studied by the experiment you did. (c) For each factor, explain why that factor influenced the current. 2 Question 11 (a) Clarify the idea of a magnetic field. 2 (b) Define magnetic field strength in terms of magnetic flux. 2 (c) Recall the units and symbol used to measure magnetic field strength. 1
7 Question 12 The diagram shows equipment used to generate a current. Assuming that the coil starts from 1 the position shown, and rotates at constant rotational speed, which graph best shows the current delivered to the external circuit by this device as it rotates through 360? Question 13 (a) Define magnetic flux. 1 (b) Define magnetic flux density. 1 (c) Using the two diagrams distinguish between magnetic flux and magnetic flux density 2 (magnetic field strength).
8 Question 14 A bar magnet is moved backwards and forwards near a coil which is connected to a data logger 1 calibrated to plot the emf induced in the coil. The graph below the diagram shows the plot obtained. The magnet was then moved back and forth near the magnet at twice the original speed. Which plot best shows the new graph produced by the data logger? (All graphs are drawn to the same scale.) Question 15 (a) A 5.0 cm squared coil with 10 turns is placed into a uniform magnetic field. The 2 magnetic flux density is 0.80 T. The angle between the plane of the coil and the magnetic field lines is 20. Calculate the magnetic flux through the coil. (b) The coil rotates from its initial position to 90. Plot the graph of the magnetic flux 4 versus the angle between the plane of the coil and the magnetic field lines.