AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
A basic transformer consists of a primary coil and a secondary coil wound…
Full specification wording
Transformers (HT only): A basic transformer consists of a primary coil and a secondary coil wound on an iron core.
A transformer is two separate coils of insulated wire wound on the same iron core.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 1 of 3
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A transformer is two separate coils of insulated wire wound on the same iron core. The coil connected to the supply is the primary; the coil connected to the output is the secondary. They are not joined electrically, which is why the labels on a diagram matter: the primary is simply whichever coil the input reaches. The core links them magnetically. An alternating current in the primary produces a magnetic field that grows, collapses and reverses; the iron carries that changing field round to the secondary; and the changing field through the secondary induces an alternating potential difference across it. Because every step depends on the field changing, a transformer does nothing at all with a direct current supply, however large that supply is.
What earns the marks
- Naming the primary coil as the one connected to the input supply.
- Naming the secondary coil as the one connected to the output.
- The iron core linking the two coils magnetically.
- Stating that the two coils are not connected to each other electrically.
Common mistakes and how to put them right
Labelling the coils by size rather than by which one the supply is connected to.
Drawing a wire joining the primary circuit to the secondary circuit.
Saying a transformer works on direct current, when a steady current gives an unchanging field and no output.
Calling the core a magnet, rather than a material that carries the changing magnetic field.
Exam tips
- Trace the input wires on the diagram to find the primary before you answer anything else.
- Learn the three labels, primary coil, secondary coil and iron core; they appear as a quick two mark question.
- Write alternating every time you mention the supply to a transformer.
Try the lesson
The start of the Transformers (HT only): A basic transformer consists of a primary coil and a secondary coil wound on an iron core. lesson, made from checked teaching notes for this specification point.
Have a go first
Which description accurately outlines the construction of a basic transformer?
Listen
A transformer is two separate coils of insulated wire wound on the same iron core. The coil connected to the supply is the primary; the coil connected to the output is the secondary. They are not joined electrically, which is why the labels on a diagram matter: the primary is simply whichever coil the input reaches. The core links them magnetically. An alternating current in the primary produces a magnetic field that grows, collapses and reverses; the iron carries that changing field round to the secondary; and the changing field through the secondary induces an alternating potential difference across it. Because every step depends on the field changing, a transformer does nothing at all with a direct current supply, however large that supply is. A strong answer earns marks for these points. naming the primary coil as the one connected to the input supply. naming the secondary coil as the one connected to the output. the iron core linking the two coils magnetically. stating that the two coils are not connected to each other electrically. Exam tip: Trace the input wires on the diagram to find the primary before you answer anything else.
Key words
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primary coil
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secondary coil
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iron core
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magnetic linking
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See every definition
- primary coil
- The coil connected to the input supply, which is simply whichever coil the input reaches.
- secondary coil
- The coil connected to the output, which is not joined electrically to the primary coil.
- iron core
- The material on which the two coils are wound, carrying the changing magnetic field round to the secondary.
- magnetic linking
- The core links the two coils magnetically, so the changing field through the secondary induces an alternating potential difference across it.
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