P6 Revision Questions Motors And Generators

Transcript

Hartismere High School P6 Revision Questions Motors and Generators These are from the old specification 33 marks Remember the most appropriate questions you can do are from the specimen paper and the two CGP papers Hartismere High School 1 1. (a) Look at the pictures of household appliances. Which two appliances have a motor inside them? answer ............................................... and .................................................... [2] (b) John passes a wire through a card. He connects the wire to a battery. Look at the diagram. He sprinkles iron filings onto the card to show the shape of the magnetic field. Which is the shape of the magnetic field made by the wire? Hartismere High School 2 Choose from: A B C D answer ....................................................... [1] (c) The diagram shows part of a DC generator. Look at the diagram. Complete the diagram by adding labels to parts A and B. [2] [Total 5 marks] 2. Declan has electrical appliances in his kitchen. Some electrical appliances contain an electric motor. (a) Name one kitchen appliance that contains an electric motor. ........................................................................................................................ [1] Hartismere High School 3 (b) Look at the diagram of an electric motor. Declan connects the motor to the power supply. It spins round. (i) Declan passes more current through the motor. What happens to the motor? ............................................................................................................... [1] (ii) He puts stronger magnets in the motor. What happens to the motor? ............................................................................................................... [1] (iii) Declan now uses a coil with fewer turns. What happens to the motor? ............................................................................................................... [1] (iv) He changes the direction of the current. What happens to the motor? ............................................................................................................... [1] [Total 5 marks] Hartismere High School 4 3. This question is about how electric motors work. (a) Michael hangs a wire between the poles of a magnet. He wants to find out what happens when a current passes through the wire. The current is switched on. (i) Describe the magnetic field produced around the wire by the current. ............................................................................................................... ............................................................................................................... [1] (ii) What effect does this have on the wire? ............................................................................................................... ............................................................................................................... ............................................................................................................... [2] (b) Michael changes the direction of the current. What happens to the wire? ........................................................................................................................ [1] (c) Write down the name of one kitchen appliance that contains an electric motor. ........................................................................................................................ [1] [Total 5 marks] 4. This question is about how electric motors work. (a) Michael hangs a wire between the poles of a magnet. He wants to find out what happens when a current passes through the wire. When he switches on, the wire moves out of the gap between the poles of the magnet. Hartismere High School 5 Michael reverses the direction of the current. What difference does he see in the movement of the wire? ........................................................................................................................ [1] (b) The diagram shows a simple motor. simple electric motor coil N split-ring commutator S brushes electric current magnetic field force (motion) (i) The current in the motor is increased. What happens to the speed of rotation of the motor? ............................................................................................................... [1] (ii) How does the split-ring commutator keep the motor spinning in the same direction? ............................................................................................................... ............................................................................................................... ............................................................................................................... [2] [Total 4 marks] Hartismere High School 6 5. This question is about generating electricity. (a) Dave has some scientific equipment. He wants to generate electricity. Look at the equipment. Explain how he can use this equipment to generate electricity. You may draw a diagram as part of your answer. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ [2] (b) Electricity is generated in power stations. It is sent to homes through cables and transformers in the National Grid. (i) What is the frequency of this electricity in the UK? ..................................................................... Hz [1] (ii) Why is DC electricity not used with transformers? ............................................................................................................... [1] [Total 4 marks] Hartismere High School 7 6. Andy has made a model of a simple DC generator. A B C (a) Finish the table by identifying the parts of the DC generator. Choose words from this list. commutator coil magnet motor transformer label part of dynamo A B C [3] (b) Finish the sentence. When Andy spins the coil, a ................................ is induced across the coil. [1] (c) How is electricity generated at a power station? Put a tick ( ) in the box next to the correct answer. A bar magnet rotates inside coils of wire. An electromagnet rotates around a permanent magnet. Hartismere High School 8 An electromagnet rotates inside coils of wire. Coils of wire rotate between the poles of a permanent magnet. Coils of wire rotate inside an electromagnet. [1] [Total 5 marks] 7. Transformers are normally used to change the size of an AC voltage. A shaving socket has two outputs, 230 V and 115 V. SHAVERS ONLY 230 V (a) 115 V What type of transformer changes the 230 V mains supply to 115 V? ........................................................................................................................ [1] (b) The input to the transformer is 230 V. There are 10 000 turns on the primary coil of the transformer. The output is 115 V. How many turns are there on the secondary coil? Use the equations on page 2 to help you. ........................................................................................................................ ........................................................................................................................ number of turns on secondary coil = .......................................................... [2] (c) An isolating transformer is used between the 230 V mains supply and the 230 V outlet. Why is there an isolating transformer in a shaver socket? Hartismere High School 9 ........................................................................................................................ [1] (d) Naseer is reading about his new rechargeable shaver. He looks at the label on the charger. AC – DC adaptor Input 230 V ~ 50 Hz Output 2.8 V 1200 mA What is the frequency of the mains electricity supply in the UK? ....................................... [1] [Total 5 marks] Hartismere High School 10