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.
To help you plan your year 11 physics lesson on: Transformers, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 11 physics lesson on: Transformers, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
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Explore more key stage 4 physics lessons from the Mains electricity unit, dive into the full secondary physics curriculum, or learn more about lesson planning.
Licence
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