Wikibooks: GCSE Science/Transformers
Transformers are devices that use induction to transform a high a.c. voltage to a low one or vice versa. They are incredibly important devices and (even more importantly) they are examiners favourites. On this page you will be looking at how a transformer works and how they are used. You will also b...
| Format: | Book |
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| Language: | English |
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| Online Access: | https://en.wikibooks.org/wiki/GCSE_Science/Transformers |
| Summary: | Transformers are devices that use induction to transform a high a.c. voltage to a low one or vice versa. They are incredibly important devices and (even more importantly) they are examiners favourites. On this page you will be looking at how a transformer works and how they are used. You will also be given some practice in using some simple equations that let you work out what the output voltage and current must be. =How a transformer works= There is nothing new to learn in this section. You ve already covered [[GCSE Science/Magnetic effects of a current]] and [[GCSE Science/Induction]]. This section used ideas from those two pages to understand a transformer. The simplest transformer consists of a soft iron core with two coils of wire independently wrapped around it. The first coil called the primary coil is connected to an a.c. power supply. The other coil called the secondary coil is connected to the output. The current in the primary coil causes a magnetic field. It s just an electromagnet but because the current is a.c. the magnetic field is constantly changing. If we consider one end of the soft iron core it s first a north pole then the field gets weaker and weaker until it becomes zero then it starts to build up and the end becomes a south pole. The process repeats and the end becomes a north pole again. Now let s think about what is going on in the secondary coil. The magnetic field of the first coil passes right through the secondary coil what s more the field is constantly changing. This changing field induces a current in the secondary coil. So even though the coils are not physically connected the current in one causes the current through the other. If you imagine the lines of field they appear to pulse as the field grows stronger and weaker. When the field grows weak they sweep inwards cutting the secondary coil. Q1) What would the current in the secondary coil be like if you used d.c. in the primary coil? d.c. in the primary coil will not create any current in the secondary coil. Transformers are ... |
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