Trace transformer roles in high-voltage electricity transmission
Follow generation, step-up transmission and later step-down supply through a labelled conceptual network.
Section 4.5.6 · The transformer
Exam scope and assessment notes
Core and Extended · Physics 0972, 2026–2028. Use the stated source, operating conditions and meter ranges. Written practice is self-checked. Human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0972 has the same subject content as IGCSE 0625, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Use step-up/down terms.
- Distinguish voltage from energy.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why should input/output roles be assigned separately at each stage?
What you will learn
- Follow generation, step-up transmission and later step-down supply through a labelled conceptual network.
- Explain step-up and step-down transmission roles with local winding labels and a conserved transfer account.
Follow the voltage stages
A high-voltage transmission system can use a step-up transformer near generation to raise the a.c. voltage for long-distance transfer. Step-down transformers later reduce voltage for distribution and suitable consumer supply. Identify input/output roles separately at each transformer; the network is not one winding pair stretching from generator to every home.
The long-distance high-voltage stage helps reduce current for the same transferred power. The later lower-voltage stages suit the connected distribution and user equipment. Voltage values vary by real system; the values in this lesson are supplied examples, not national wiring standards.
Keep the transfer boundary explicit
Electrical energy is transferred through connected sources, transformers, cables and loads. A step-up stage does not create extra energy merely because voltage is larger. Real transformers and cables have losses and operating limits.
A network diagram is a conceptual account of transformer use, not a safe procedure for accessing transmission equipment or household wiring. Keep the generation-to-load sequence and each transformer’s voltage change clear before making power or loss calculations.
Pause and explain
A stage changes 200 kV to 10 kV. What is its role?
Worked example
A supplied conceptual system goes from 20 kV generation to 200 kV transmission, then to 10 kV distribution. Classify the two transformer stages.
Show the worked solution
- 20 kV to 200 kV increases voltage.
- 200 kV to 10 kV decreases voltage.
- The stages are step-up then step-down.
Answer Step-up, then step-down.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Classify 20 kV → 200 kV → 10 kV transformer changes.
Give me a hint
Compare output with input at each arrow.
Compare my reasoning
- The first increases voltage tenfold.
- The second reduces voltage.
- The roles are step-up then step-down.
Step-up then step-down.
Look for these in your work
- Identify both stages.
- Keep the network order.
Explain why the last conceptual transformer reduces voltage before specified user equipment.
Give me a hint
Connect voltage stage to the intended equipment supply.
Compare my reasoning
- Long-distance transmission uses a high-voltage stage.
- The connected later equipment needs its specified supply conditions.
- A step-down stage provides the lower-voltage model output.
To provide the specified lower-voltage supply stage.
Look for these in your work
- Distinguish transmission and use.
- Retain equipment-specific requirements.
A report calls the entire network one transformer and says its step-up stage multiplies energy. Correct it.
Give me a hint
Separate connected stages from winding roles and energy.
Compare my reasoning
- The network contains multiple source, cable, transformer and load stages.
- Each transformer has its own primary and secondary.
- Voltage increase does not create an energy input.
Multiple connected stages transfer energy; a step-up transformer does not create it.
Look for these in your work
- Correct the topology.
- Correct the energy claim.
Common mistakes
- Classify each stage separately.
- Example voltages are not wiring standards.
- Higher voltage does not create energy.
What can you explain now?
Where is a step-up transformer used in this conceptual transmission sequence?
Compare with the explanation
Before the long-distance high-voltage stage
The generation-side step-up raises voltage for the long-distance transmission stage.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain step-up and step-down transmission roles with local winding labels and a conserved transfer account.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.