Transformers 5.0 / 5 based on 3 ratings ? PhysicsElectricityGCSEAQA Created by: CharCreated on: 21-05-13 20:33 What does a transformer consist of? Two coils of insulated wire 1 of 18 What are these coils called? The primary coil and the secondary coil 2 of 18 Are they wound on the same iron core? Yes 3 of 18 When an alternating current passes through the primary coil, it produces what? An alternating magnetic field in the core 4 of 18 What does the magnetic field continually do? Expands and collapses 5 of 18 Which coil does the alternating magnetic field lines pass through? The secondary coil 6 of 18 And do what to the alternating potential difference across its ends? Induce it 7 of 18 What does the secondary coil have to be part of to produce an alternating current? A complete circuit 8 of 18 Why are the coils of wire insulated? So that the current does not short across either the iron core OR adjacent turns of wire 9 of 18 But flows instead around? The whole coil 10 of 18 Why is the core made of iron? So it is easily magnetised 11 of 18 What are transformers used in? The National Grid 12 of 18 Step up transformer = Secondary coil GREATER THAN the pd across the primary coil (secondary coil has MORE turns than its primary coil) 13 of 18 Step down transformer = Secondary coil LESS THEN the pd across the primary coil (secondary coil has FEWER TURNS than its primary coil) 14 of 18 What do transformers only work with - ac or dc? AC 15 of 18 Why? Because DC would not be continually expanding and collapsing, so no potential diff would be induced in the secondary coil 16 of 18 What is the switch mode transformer core made of? Ferrite 17 of 18 What is different of a switch mode transformer compared to a traditional transformer? Operates at a higher frequency, is lighter and smaller and uses very little power when there is no device connected across its output terminals 18 of 18
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