Transformers
I can describe how a transformer works and solve problems using transformer equations.
Transformers
I can describe how a transformer works and solve problems using transformer equations.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- A potential difference that causes a current to flow in the primary coil magnetises the iron core.
- When the iron core is magnetised, it induces a potential difference across the secondary coil.
- An AC gives the changing magnetic field needed to induce a potential difference across the secondary coil.
- Transformers are almost 100% efficient so the power output is equal to the power input.
- The ratio of the number of turns on the coils is equal to the ratio of the potential differences across them.
Keywords
Primary coil - a coil of insulated wire in a transformer, across which potential difference is applied
Secondary coil - a coil of insulated wire in a transformer, across which potential difference is induced
Soft iron core - pure iron inside the coil of an electromagnet that loses all of its magnetism when the electromagnet turns off
Induced p.d. - the p.d. across a conductor caused by a magnetic field moving relative to it
Efficiency - the proportion or percentage of energy supplied to a device that is transferred in a useful way
Common misconception
The size of the current in the primary coil controls the size of current in the secondary coil.
Explain how the p.d. across and resistance of the secondary circuit determines the secondary p.d. and therefore current, and how the current adjusts to ensure that the power input is equal to the power output.
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Starter quiz
6 Questions
describes the coil across which p.d. is applied
describes a transformer that increases the p.d.
describes a transformer that decreases the p.d.
describes the coil across which p.d. is induced
25 kV
33 kV, 11 kV or 450 V
230 V
400 kV