Electromagnetic Induction

Transcription

1 Electromagnetic Induction Question Paper Level ubject Exam oard Unit Topic ooklet O Level Physics ambridge International Examinations Electricity and Magnetism Electromagnetic Induction Question Paper Time llowed: 64 minutes core: /53 Percentage: /1 Grade oundaries:

2 For more awesome GE and level resources, visit us at 1 Electrical power is transmitted by cables over long distances at very high s. What are the effects of using a high transmission system? 2 Electric power cables transmit electrical energy over large distances using high-, alternating current. What are the advantages of using a high and of using an alternating current? advantage of using a high high current is produced in the cable high current is produced in the cable less energy is wasted in the cable less energy is wasted in the cable advantage of using an alternating current the resistance of the cable is reduced the can be changed using a transformer the resistance of the cable is reduced the can be changed using a transformer

3 For more awesome GE and level resources, visit us at 3 s a magnet is moved into the coil of wire as shown, there is a small reading on the sensitive ammeter. Which change increases the size of the reading? moving the opposite pole into the coil pulling the magnet out of the coil pushing the magnet in faster unwinding some of the turns of wire 4 n ideal transformer has a primary of 6 V and a secondary of 24 V. The secondary coil is attached to a resistor of resistance 12 Ω. primary coil secondary coil 6 V 24 V 12 Ω What is the power dissipated in the resistor and the current in the primary coil?

4 For more awesome GE and level resources, visit us at 5 The diagram shows a d.c. motor with its coil horizontal. axle Why is a split-ring commutator used? d.c. supp to change the current direction in the coil as the coil passes the horizontal position to change the current direction in the coil as the coil passes the vertical position to change the current direction in the d.c. supply as the coil passes the horizontal position to change the current direction in the d.c. supply as the coil passes the vertical position 6 Which graph shows the output of an a.c. generator when the coil makes one complete revolution?

5 For more awesome GE and level resources, visit us at 7 student moves a magnet into a coil of wire as shown in the diagram. The coil of wire is connected to a sensitive ammeter. coil magnet ammeter Which change does not produce an increase in the reading? increasing the number of turns on the coil increasing the resistance of the ammeter increasing the speed of the magnet increasing the strength of the magnet 8 The diagram shows a simple d.c. motor. Which labelled part is the commutator?

6 For more awesome GE and level resources, visit us at 9 transformer is used to operate a 12 V lamp from a 25 V mains supply. transformer 25 V.1 12 V 2. The mains current is.1. The current in the lamp is 2.. What is the efficiency of the transformer?

7 For more awesome GE and level resources, visit us at 1 The graph shows the output of an a.c. generator. The coil in the generator rotates 2 s in one second.

8 For more awesome GE and level resources, visit us at 11 Which material is used for the core of a transformer and why? material copper copper iron iron reason good conductor of electricity easy to magnetise and demagnetise good conductor of electricity easy to magnetise and demagnetise 12 current is produced when a wire is moved between two magnets as shown. ammeter movement of wire Which device uses this effect? a battery a generator a motor an electromagnet 13 Why is a transformer used to connect a generator in a power station to a long-distance transmission line? to decrease the and decrease the current to decrease the and increase the current to increase the and decrease the current to increase the and increase the current

9 For more awesome GE and level resources, visit us at 14 bar magnet is pushed into one end of a long coil connected to a sensitive meter. bar magnet coil sensitive meter Which of the following affects the magnitude of the deflection of the meter? the direction in which the coil is wound the speed with which the magnet enters the coil which end of the coil is used which pole of the magnet enters first 15 Which graph represents the output of a simple a.c. generator?

10 For more awesome GE and level resources, visit us at 16 The diagram shows the -pole of a magnet moving into, and out of, a coil of wire. magnet X coil of wire This movement produces a current in the coil of wire. The current produces a magnetic pole at X. Which pole is produced at X when the magnet is moved in and when it is moved out?

11 For more awesome GE and level resources, visit us at 17 simple a.c. generator produces an alternating e.m.f. as shown. 1. e.m.f. / V 1. 2 / s _ 1. The speed of the generator is doubled. Which graph best represents the new output? 1. e.m.f. / V _ / s e.m.f. / V _ / s _ e.m.f. / V 1. 2 / s _ e.m.f. / V _ / s _ 2.

12 For more awesome GE and level resources, visit us at 1 magnet is moved towards a coil of insulated wire. voltmeter connected across the coil shows a positive reading. What produces a higher reading on the voltmeter? moving the magnet away from the coil at the same speed moving the magnet away from the coil at a slower speed moving the magnet towards the coil at a faster speed moving the magnet towards the coil at a slower speed 1 The diagram shows the output of an a.c. generator as displayed on a cathode-ray oscilloscope. The horizontal scale is 5 ms / cm. 1 cm What is the for one complete rotation of the coil of the generator? 5 ms 1 ms 2 ms 3 ms 2 The electromotive force (e.m.f.) induced in a conductor moving at right-angles to a magnetic field does not depend upon the length of the conductor. the resistance of the conductor. the speed of the conductor. the strength of the magnetic field.

13 For more awesome GE and level resources, visit us at 21 The diagram shows part of an a.c. generator when its coil is in a horizontal position. magnet coil The graph shows the output plotted against. Which point on the graph shows when the coil is in a vertical position? output 22 The diagrams show three electrical devices, X, Y and Z. coil rotation soft iron rotation coil rotation axis cylindrical magnet coil X Y Z Which devices provide an alternating current (a.c.) output? X only Y only X and Y X and Z

14 For more awesome GE and level resources, visit us at 23 small coil is connected to a galvanometer G, as shown. G When a magnet is allowed to fall towards the coil, the galvanometer pointer gives a momentary deflection to the right of the zero position. The magnet moves through the coil. What happens to the galvanometer pointer as the magnet falls away from the coil? It gives a continuous reading to the left. It gives a momentary deflection to the left. It gives a continuous reading to the right. It gives a momentary deflection to the right.

15 For more awesome GE and level resources, visit us at 24 magnet is pushed slowly into a coil and there is a current in the coil in the direction shown. magnet current The magnet is then pulled out quickly from the same end of the coil. What happens to the direction and the size of the current? 25 The diagram shows an a.c. generator connected to an electrical circuit (load resistor). coil of many turns axle mechanical drive slip rings Which statement is correct? load resistor The direction of the potential difference across the load resistor is always the same. The size of the induced e.m.f. depends on the number of turns in the coil. The size of the induced e.m.f. does not change as the coil turns. Winding the coil on a soft-iron cylinder makes no difference to the induced e.m.f.

16 For more awesome GE and level resources, visit us at 26 The diagram shows an a.c. generator connected to a resistor. coil of many turns axle mechanical drive slip rings resistor ome changes are made, one at a. The speed of the drive is changed. The strength of the magnets is changed. The number of turns in the coil is changed. The value of the resistor is changed. How many of these alter the value of the e.m.f. generated in the coil?

17 For more awesome GE and level resources, visit us at 34 simple a.c. generator produces a that varies with as shown. / V / s Which graph shows how the varies with when the generator rotates at twice the original speed? / V / s 2 / V / s 2 / V / s 2 / V / s 2

18 For more awesome GE and level resources, visit us at 28 Why is electrical energy usually transmitted at high? s little energy as possible is wasted in the transmission cables. The current in the transmission cables is as large as possible. The resistance of the transmission cables is as small as possible. The transmission system does not require transformers. 29 magnet is pushed horizontally towards a coil of wire, inducing an e.m.f. in the coil. magnet In which direction does the induced e.m.f. make the coil move? away from the magnet towards the magnet downwards upwards

19 For more awesome GE and level resources, visit us at 3 The graph shows the output of an a.c. generator. The coil in the generator rotates 2 s in one second.

20 For more awesome GE and level resources, visit us at 31 Why is a transformer used to connect a generator in a power station to a long-distance transmission line? to decrease the and decrease the current to decrease the and increase the current to increase the and decrease the current to increase the and increase the current 32 conductor is moving horizontally across a vertical magnetic field. conductor movement of conductor n e.m.f. is induced in the conductor. o deflection is seen on the ammeter. What is the reason for this? The ammeter is not between the poles. The conductor is moving too slowly. The conductor is not cutting field lines. The poles are too close together.

21 For more awesome GE and level resources, visit us at 33 Which transformer arrangement produces an output that is larger than the input? iron core iron core d.c. input output a.c. input output iron core iron core d.c. input output a.c. input output 34 Which diagram shows how the output of a simple a.c. generator varies with?

22 For more awesome GE and level resources, visit us at 35 The diagram shows a working transformer. input (primary coil) output (secondary coil) Which statement is correct? The input is d.c. The input is greater than the output. The input is less than the output. The input is the same as the output. 36 The diagram shows how a magnet and a coil may be used to induce an electric current. coil moving towards magnet magnet How could the ammeter reading be increased? Move the coil more slowly. Put a resistor in series with the ammeter. Turn the magnet round, then move the coil. Use a coil with more turns.

23 For more awesome GE and level resources, visit us at 37 small coil is connected to a sensitive ammeter. The ammeter needle can move to either side of the zero position. s the magnet falls towards the coil, the ammeter needle moves quickly to the right of the zero position. The magnet moves through the coil. How does the ammeter needle move as the magnet falls away from the coil? It does not move. It gives a steady reading to the right. It moves quickly to the left of the zero position and then returns to zero. It moves quickly to the right of the zero position and then returns to zero. 38 The diagram shows transformers and cables used to transmit electrical energy over long distances. power station transformer X transformer houses How does transformer X affect the and the current from the power station? current decreases it decreases it decreases it increases it increases it decreases it increases it increases it

24 For more awesome GE and level resources, visit us at 39 permanent magnet moving up and down on the end of a spring induces an e.m.f. in a coil. spring support movement permanent magnet coil Which factor, on its own, would decrease the maximum value of the induced e.m.f.? increasing the number of turns in the coil increasing the strength of the magnet raising the coil raising the support of the spring

25 For more awesome GE and level resources, visit us at 4 transformer has more turns on the secondary coil than on the primary. The graph shows how the input varies with. Which graph, drawn to the same scale as the input graph, shows how the output varies with?

26 For more awesome GE and level resources, visit us at 41 n alternating current is passed through a wire stretched between the poles of a magnet. a.c. supply Which way will the wire move? left and right right only up and down up only 42 girl turns the handle of a small a.c. generator four s each second. The generator produces a maximum output of.5 V. Which of the following graphs best shows this?.5 output /V.5 1 / s.5 output /V / s output /V.5 1 / s.25 output /V / s.25.25

27 For more awesome GE and level resources, visit us at 43 Which statement about the action of a transformer is correct? n e.m.f. is induced in the secondary coil when an alternating is applied to the primary coil. n e.m.f. is induced in the secondary coil when there is a steady direct current in the primary coil. The current in the secondary coil is always larger than the current in the primary coil. The in the secondary coil is always larger than the in the primary coil. 44 Electrical energy is transmitted at high alternating s. What is not a valid reason for doing this? t high, a.c. is safer than d.c. For a given power, there is a lower current with a higher. There is a smaller power loss at higher and lower current. The transmission lines can be thinner with a lower current. 45 Why can birds stand on an overhead high transmission line without suffering any harm? Their bodies have a very high resistance. Their feet are very good insulators. The spaces between their feathers act as insulators. They are not connected to earth.

28 For more awesome GE and level resources, visit us at 46 step-up transformer with 1 % efficiency has an input of 3 V and an input current of 2. input 3 V output Under these conditions, what output and output current could be obtained? output / V output current / student pushes the -pole of a bar magnet into the end Q of a long solenoid and observes a deflection to the right on the sensitive ammeter. P Q What will produce a deflection in the same direction? pulling the -pole out of end Q pulling the -pole out of end P pushing the -pole into end P pushing the -pole into end P

29 For more awesome GE and level resources, visit us at 48 step-down transformer changes 24 V a.c. to 12 V a.c. There are 6 turns on the primary coil. How many turns are on the secondary coil? Why are high s and low currents used to transmit electrical energy over long distances? to increase the electromagnetic radiation to increase the speed at which electrons move to reduce heat loss from the power line to reduce the resistance of the power line 5 The number of turns between each pair of output terminals of a transformer is shown in the diagram. 6 V 2 turns 1 turns 2 turns 4 turns P Q R etween which two terminals will the output be 12 V? Pand Q Qand R Rand P and R

30 For more awesome GE and level resources, visit us at 52 The diagram shows a metal bar swinging like a pendulum across a uniform magnetic field. The motion induces an e.m.f. between the ends of the bar. pivot magnetic field P Which graph represents this e.m.f. during one complete oscillation of the bar, starting and finishing at P? e.m.f. e.m.f. e.m.f. e.m.f.

31 For more awesome GE and level resources, visit us at 52 Why is electricity transmitted along power lines at very high s? to reduce the resistance of the cables so that transformers can be used to make sure that the current is the same all the way along the power lines to reduce loss of energy 53 small coil is connected to a galvanometer as shown below. When the magnet is allowed to fall towards the coil, the galvanometer pointer gives a momentary deflection to the right of the zero position. galvanometer The magnet moves through the coil and, as it falls away from the coil, the galvanometer pointer gives a continuous reading to the left. gives a momentary deflection to the left. gives a momentary deflection to the right. gives a continuous reading to the right.