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First Name: ………………………….. Last Name: ………………………….. ______ School Year 12 Physics Half Yearly Examination 2008 Section A: Section B: TOTAL: /36 /44 / 80 Section A Multiple Choice Questions SHADE the right answer. 1 3 5 7 9 10ii 11 13 15 17 19 21 A A A A A A A A A A A A B B B B B B B B B B B B C C C C C C C C C C C C D D D D D D D D D D D D 2 4 6 8 10i 10ii i 12 14 16 18 20 22 A A A A A A A A A A A A B B B B B B B B B B B B C C C C C C C C C C C C D D D D D D D D D D D D Yr 12 Physics Half Yearly Examination 2008 23 25 27 29 31 33 A A A A A A B B B B B B C C C C C C D D D D D D 24 26 28 30 32 34 A A A A A A B B B B B B C C C C C C D D D D D D Please turn over. 2 Yr 12 Physics Half Yearly Examination 2008 Section A Multiple Choice Questions 1 I x x x B x x x x x x x x x x x x x x x x x The force on the current carrying wire in the above magnetic field B can be (A) increased by changing the angle to the field lines. (B) increased by spacing the field lines out more. (C) decreased by decreasing the thickness of the wire. (D) increased by changing I from 1.25 A to 1.5 A. 2 As a conductor with a 2.5A current is slowly rotated in a 0.5T magnetic field, which position will produce the greatest force? x x W x X x xx (A)W (B)X (C)Y (D)They will all be the same x x x Y x x x x x x x x x x x x x x x x 3 Yr 12 Physics Half Yearly Examination 2008 3 I I These two conductors are 1m apart and each carry 0.05A of current. They will (A) attract each other. (B) have no effect on each other. (C) push each other away. (D) slowly rotate around each other. 4 Calculate the force between two parallel wires, each 1 m long, if they carry 3A of current and are 2 m apart in a vacuum. (k = 2.0 x 10-7) (A) 4.5 x 10-7 N (B) 18 x 10-7 N (C) 9.0 x 10-7 N (D)9.0 N 5 I1 1.4m 0.7 A 2m Calculate the value of the unknown current if the force between the conductors is 3.0 x 10-5. (k = 2.0 x 10-7) (A)3.0A (B)0.5A (C) 150A (D)1.5A 4 Yr 12 Physics Half Yearly Examination 2008 6 Torque is (A) the greatest when the force is applied to the point of rotation. (B) defined in terms of Newtons per Amp. (C) the turning moment of a force. (D) the greatest when a current carrying conductor is parallel to the field lines. 7 Pivot point F Calculate the force needed to produce a torque of 50 N.m when applied to the half way point on a 5m swivelling rod. (A)4 N (B)125 N (C)50 N (D)20 N 8 Electric motors (A) convert potential energy into electrical motion. (B) convert mechanical energy into potential energy. (C) change electrical energy into mechanical energy. (D) change motion into mechanical energy. 9 In an electric motor, which of the following would ensure that torque is kept near its maximum during each revolution? (A) Place the rotor in a radial magnetic field. (B) Keep the current coming into the motor constant. (C) Keep both the current and magnetic field strength constant. (D) Keep the magnetic field strength as constant as possible. 5 Yr 12 Physics Half Yearly Examination 2008 10 X Y V i W If a current is sent through this circuit from V to W, then (A) the magnetic field intensity will decrease. (B) the loop will rotate. (C) the loop will move up. (D) the loop will move down. ii If a current is sent through this circuit from W to V then, (A) the force on the conductor will be up at X. (B) the force on the conductor will be up at Y . (C) the loop will move up. (D) the loop will move down. iii Assume this loop is parallel to the magnetic field shown. Calculate the torque if the loop contains 12 turns, current is 1.5A, the loop sides are 30 cm by 20 cm and the magnetic field strength is 0.5T. (A)0.54 (B)0.045 (C)5400 (D)900 11 What does DC and AC stand for? (A)Double current and alternate current (B)Direct current and alternating current (C)Double current and alternating current 6 Yr 12 Physics Half Yearly Examination 2008 (D) Developing current and anti-current 12 1. Supply the magnetic field 2. The spinning centre of the motor 3. To reverse the current 4. Contacts to take the current in and out of the motor 5. Conduct the electricity Which of the following lists correctly fit the above descriptions for the working parts of a DC motor? Commutat or 3 2 3 5 Wire 5 4 5 4 Rotor 2 3 1 2 Brushes 4 5 2 3 Magnets 1 1 4 1 (A) (B) (C) (D) 13 X N W Y S Z DC Commutator Motor In the above end view of a DC motor the armature (WY) rotates clockwise when a current is applied. What happens to the current in the wire at W as it rotates over to a position between X and Y on the other side? (A) It moves faster. (B) The current reverses. (C) The current stays the same to keep the torque going. 7 Yr 12 Physics Half Yearly Examination 2008 (D) The current fluctuates every ¼ of a turn, so it is about to change. 8 Yr 12 Physics Half Yearly Examination 2008 14 S N X S N At position X in the above diagram, (A) there will be only air. (B) there will be a magnetic field. (C) the magnetic fields cancel out. (D) a current will be moving from the N to the S across X. 15 DC commutator motors (A) can only use permanent magnets to supply a magnetic field. (B) can have a magnetic field supplied by either a permanent magnet or an electromagnet. (C) cannot operate with electromagnets because they interfere with the current in the commutator. (D) need alternating current supplied to the commutator if electromagnets are used. 16 A square coil with 10 windings (turns) and a side length of 10 cm is placed at 60o to a 0.5 T magnetic field. Calculate the current in the coil when a 0.2 N.m torque is being applied. (A) 8 x 10-3A (B) 1 x 10-3 A (C)8 A (D)0.5 A 17 The transmission of electricity over large distances is carried out at high voltages, typically 330 to 500 kV. Which of the following is a valid reason for using these voltages? (A)High voltages are less affected by fluctuations in the demand from houses and industry. (B)High voltages are easier to send through the transformers. 9 Yr 12 Physics Half Yearly Examination 2008 (C)There is more power loss during conduction at lower voltages. (D)The high voltage repels most lightning bolts. 18 A student drew the following diagram of an experiment she was conducting. As she moves the magnet towards the coil, as shown, which of the following would be a correct observation? (A)The coil will be drawn towards the magnet. (B) A current will be moving from B to A. (C) The coil will have a south pole induced at Y . (D) A current will be fluctuating between A and B. 19 5A Primary Secondary 11 kV 240 V Assuming that the power in the primary coil is equal to the power in the secondary coil, calculate the current induced in the secondary coil of the above transformer. (A) 2.29 x 10-1 A (B) 1.09 x 10-1 A (C)229 A (D)29 A 10 Yr 12 Physics Half Yearly Examination 2008 20 Three rings are dropped at the same time over identical magnets as shown below. Which of the following describes the order in which the rings P, Q and R reach the bottom of the magnets? (A) They arrive in the order P, R, Q. (B) They arrive in the order P, Q, R. (C) Rings P and R arrive simultaneously, followed by Q. (D) Rings Q and R arrive simultaneously, followed by P. 21 A transformer is to be designed so that it is efficient, with heating by eddy currents minimised. The designer has some iron and insulating material available to build the transformer core. The windings are to be made with insulated copper wire. Which of the following designs minimises the energy losses in the core? 11 Yr 12 Physics Half Yearly Examination 2008 12 Yr 12 Physics Half Yearly Examination 2008 22 If an object's weight on the moon is 25, then what is its weight on earth? (Note: g on the moon is 1.6 m.s-2 and on the Earth is 9.8 m.s-2) (A) 15.6 (B) 156 (C) 153 (D) 1.6 23 As a rocket blasts off from the surface of the Earth, (A) its gravitational attraction increases. (B) the gravitational potential energy increases. (C) the force of gravity doubles every 100km of height. (D) the gravitational potential energy decreases. 24 Einstein, Galileo and Newton all made very important discoveries concerning the universe. Which of the following lists places them in their correct chronological order starting with the earliest scientist? (A) Einstein, Galileo, Newton (B) Galileo, Newton, Einstein (C) Newton, Galileo, Einstein (D) Galileo, Einstein, Newton 25 For an object to stay in orbit above the Earth indefinitely (A) it must maintain a rocket propulsion to counteract the Earth’s gravity. (B) it must be able to skip across the upper atmosphere at a very shallow angle. (C) it needs a side ways velocity of sufficient magnitude to parallel the projectile motion with the Earth's surface. (D) it needs to get sufficient height to be out of the gravitational field. 13 Yr 12 Physics Half Yearly Examination 2008 26 A geostationary orbit (A) has a period of 12 hours. (B) is generally between 42,000 and 50,000 km above the Earth's surface. (C) requires a lot of energy to maintain and keep the satellite from moving. (D) has a period of 24 hours. 27 On re-entering the atmosphere, astronauts should not be subjected to g-forces greater than (A) 2 (B) 5 (C) 10 (D) 20 28 Communications on the planet can be (A) disrupted by increased sunspot activity. (B) affected by the strength of the deep space probe signals. (C) improved by using the power available from sunspot activity. (D) is completely reliant on the van Allen radiation belt to reflect the weak signals from the satellites down to ground stations. 29 Michelson and Morley carried out their famous experiment (A) just after Einstein announced his theory of special relativity. (B) in the 1680's. (C) in the 1780's. (D) in the 1880's. 30 Einstein's special theory of relativity (A) states that the speed of light is dependent on the speed of the source. (B) indicates that mass and time cannot be varied at high speeds. (C) states that the speed of light is independent of the source. 14 Yr 12 Physics Half Yearly Examination 2008 (D) encouraged Newton to develop his now universally accepted laws on motion. 31 If a space craft is heading out of the solar system at 0.5 times the speed of light and the captain shines a light in the direction of motion, what will be the speed of the light relative to another space ship floating motionless nearby? (A) 1.5 c (B) 0.5 c (C) 1.0 c (D) 0.75 c 32 When two observers moving at different velocities look at an event (A) they will agree on the simultaneity of the event. (B) they will see the event in the same way. (C) they will disagree on the simultaneity of the event. (D) the speed of the light from the event will be different for each observer. 33 A stationary observer watches a very fast space ship zip past at 0.5 times the speed of light. To the observer the (A) space ship will appear to be shorter. (B) space ship will appear wider. (C) space ship will appear longer. (D) time on their watch will slow down briefly. 34 Newton’s Third Law is about: (A) Inertia (B) Radar (C) Reaction forces (D) Integration 15 Yr 12 Physics Half Yearly Examination 2008 Please turn over. 16 Yr 12 Physics Half Yearly Examination 2008 Section B Short Answer Questions Question 1 i Explain why a charged particle curves when it enters a uniform magnetic field at an angle to the field lines. (3 marks) ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ii Discuss the role of the commutator in electric motors and describe how 17 Yr 12 Physics Half Yearly Examination 2008 it works. marks) (3 ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. Question 2 In your course you had to gather information to explain how induction is used in certain applications. i Explain what induction is? (2 marks) 18 Yr 12 Physics Half Yearly Examination 2008 ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ii Describe TWO applications using the information you have found. 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Question 3 A schematic diagram of a system to supply electricity to a house is shown below. 20 Yr 12 Physics Half Yearly Examination 2008 The step-down transformer in the substation has a turns ratio of 30 : 1. i line? What is the voltage carried by the high voltage transmission (1 mark) ............................................................................................................ ................................................. ii Identify the causes of the TWO main energy losses in the electricity between the power plant and the house. transmission of (4 marks) ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. 21 Yr 12 Physics Half Yearly Examination 2008 ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. iii Explain how the application of superconductivity could the system. marks) ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. (3 minimise energy loss in 22 Yr 12 Physics Half Yearly Examination 2008 ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. Please turn over. 23 Yr 12 Physics Half Yearly Examination 2008 Question 4 Draw and label both positions in the field below of a currentcarrying conductor i ii with maximum force on it with zero force on it (1 (1 mark) mark) B Please turn over. 24 Yr 12 Physics Half Yearly Examination 2008 Question 5 Outline why an electric motor turns. marks) ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. (5 25 Yr 12 Physics Half Yearly Examination 2008 ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. 26 Yr 12 Physics Half Yearly Examination 2008 Question 6 Explain what causes the acceleration during a space launch? When does it stop? (2 marks) ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. 27 Yr 12 Physics Half Yearly Examination 2008 Question 7 Describe what happens to objects that move fast through the atmosphere? Explain your answer. 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Question 8 Find the acceleration of gravity (gravitational field strength) given that Earth's radius = 6380 km 28 Yr 12 Physics Half Yearly Examination 2008 Earth's mass = 5.98 x 1024 kg Universal gravitational constant = 6.67 x 10-11 N.m2.kg-2 (4 marks) ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. 29 Yr 12 Physics Half Yearly Examination 2008 ............................................................................................................ ................................................. Please turn over. 30 Yr 12 Physics Half Yearly Examination 2008 Question 9 Tiger Woods drives a golf ball at 44.0 m/s and 300 above the fairway. Assuming the fairway is flat and air friction is zero, calculate the maximum height achieved by the ball. 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Question 10 31 Yr 12 Physics Half Yearly Examination 2008 Define “escape velocity” in regards to space exploration? 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Question 11 Briefly describe the Michelson-Morley experiment and what they discovered. (4 marks) 32 Yr 12 Physics Half Yearly Examination 2008 ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. 33 Yr 12 Physics Half Yearly Examination 2008 ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. ............................................................................................................ ................................................. 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