Transformers
A transformer is a device that changes the potential difference of an alternating current (AC). It consists of two coils of wire, a primary coil and a secondary coil, wrapped around a soft iron core. A step-up transformer increases the potential difference (has more turns on the secondary coil), while a step-down transformer decreases it (has fewer turns on the secondary coil). Transformers only work with AC.
Full topic guide: the detailed syllabus page with worked examples and common mistakes lives at studyvector.co.uk/gcse/physics/magnetism-electromagnetism/transformers.
Topic preview: Transformers
Sample stems from the StudyVector question bank (AQA · Edexcel · OCR) — not generic filler text.
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Coverage and provenance
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Topic explanation
A transformer is a device that changes the potential difference of an alternating current (AC). It consists of two coils of wire, a primary coil and a secondary coil, wrapped around a soft iron core. A step-up transformer increases the potential difference (has more turns on the secondary coil), while a step-down transformer decreases it (has fewer turns on the secondary coil). Transformers only work with AC.
Transformers is easiest to revise when it is treated as a precise exam behaviour, not a loose note-taking category. In GCSE Physics, the goal is to recognise how the topic appears in a question, identify the command word, and decide what evidence, method, or vocabulary earns marks. StudyVector keeps this page tied to AQA · Edexcel · OCR language where coverage is available, then routes practice towards the same topic so revision moves from explanation into retrieval.
A strong revision session starts with a short recall check. Write down the rule, definition, process, or method linked to Transformers before looking at any notes. Then answer one exam-style prompt and compare your answer with the mark-scheme logic: did you make a clear point, support it with the right step, and avoid drifting into a nearby topic? This matters because many lost marks come from almost-correct answers that do not match the expected structure.
Use this guide as the first layer: understand the topic, look at the worked examples, complete the mini quiz, then move into full practice. The full StudyVector practice loop is designed to capture whether mistakes are caused by knowledge, method, language, or timing. That distinction is important. If the error is factual, you need reteaching. If the error is method-based, you need a worked retry. If the error is wording, you need command-word calibration. That is how Transformers becomes a controlled revision target rather than another page in a folder.
Lost marks → repair task
Why marks are usually lost here
These are the error patterns StudyVector looks for after an attempt. The goal is not a generic explanation; it is one repair move and one follow-up question.
Unit, formula, or method slip
Examiner move: Select the correct method and keep units, substitutions, signs, and rounding visible.
Repair drill: Redo the calculation or method line slowly, naming the formula before substituting values.
Missing chain of reasoning
Examiner move: Show the link between point, method, evidence, and conclusion instead of jumping to the final line.
Repair drill: Write the missing because/therefore step, then retry one isomorphic question.
Weak evidence or data reference
Examiner move: Use a precise value, quote, example, diagram feature, or syllabus term to support the claim.
Repair drill: Add one concrete reference to the answer and remove any generic sentence that does not earn a mark.
Mini quiz
Use these checks before full practice. They test topic recognition, exam technique, and whether you can connect the explanation to a marked response.
1. What should you check first when a Transformers question appears in GCSE Physics?
- A.The command word and the exact topic focus
- B.The longest paragraph in your notes
- C.A memorised answer from a different topic
2. Which revision action gives the strongest evidence that Transformers is improving?
- A.Rereading the explanation twice
- B.Answering a timed exam-style question and reviewing lost marks
- C.Highlighting every key phrase in the topic notes
Sample questions
Topic-specific public question previews are still being reviewed. We keep them off public pages until the topic match is safe.
Exam tips
- Read the command word carefully — "explain" needs reasons; "state" expects a short fact.
- For Transformers, show structured working even when you are practising multiple choice — it builds accuracy under time pressure.
- Mark yourself against the mark scheme style: one clear point per mark, in logical order.
- Come back to this topic after a day or two; short spaced reviews beat one long cram.
Worked examples
Example 1
Modelled exam response
A transformer has 200 turns on the primary coil and 2000 turns on the secondary coil. If the input potential difference is 230V, what is the output potential difference? Solution: Use the transformer equation: Vp/Vs = Np/Ns. 230V / Vs = 200 / 2000. Vs = 230V x (2000 / 200) = 2300V. This is a step-up transformer.
Example 2
Identify the task before answering
Question type: a Transformers prompt asks for a clear response in GCSE Physics. Step 1: underline the command word. Step 2: name the exact part of Transformers being tested. Step 3: decide whether the mark scheme wants a definition, method, explanation, comparison, or calculation. Why it works: most weak answers fail before the content starts because they answer the topic generally rather than the exact exam task.
Example 3
Turn feedback into a repair task
Suppose your answer shows partial understanding but loses marks for precision. First, rewrite the missing mark as a short target: "I need to state the mechanism, unit, reason, or evidence explicitly." Then answer one similar question without notes. Finally, compare the second attempt with the first and check whether the same mark was recovered. Why it works: Transformers improves faster when feedback creates a specific retry, not another passive reading session.
Next revision routes from this subject
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Common mistakes
- Thinking that transformers can work with direct current (DC). They rely on a changing magnetic field, which is only produced by AC.
- Confusing step-up and step-down transformers. Step-up increases voltage (more secondary turns), step-down decreases voltage (fewer secondary turns).
- Assuming that transformers create energy. They are very efficient, but they cannot create energy. If the voltage is stepped up, the current must be stepped down to conserve power (P = VI).
Exam board notes
A Higher Tier topic for all major GCSE Physics boards (AQA, Edexcel, OCR). The transformer equations are important.
FAQs
Why are transformers used in the National Grid?
Step-up transformers are used to increase the voltage for transmitting electricity over long distances. This reduces the current, which in turn reduces energy loss as heat in the cables. Step-down transformers are then used to reduce the voltage to a safe level for use in homes and businesses.
What is the transformer equation?
The ratio of the potential differences across the coils is equal to the ratio of the number of turns on the coils: Vp/Vs = Np/Ns. For an ideal (100% efficient) transformer, the power in equals the power out: VpIp = VsIs.
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