Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want transformers — primary and secondary coils, turns ratio and power transmission — to become a reliable source of marks instead of a confused ratio calculation.
What query it owns: how to understand and revise transformers in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the transformer revision-guide angle, while Tutopiya’s Transformer subtopic page owns the learning resource and the free Transformer quiz owns the practice.

A transformer changes alternating voltage using electromagnetic induction: an alternating current in the primary coil creates a changing magnetic field in the iron core, inducing an e.m.f. in the secondary coil. Cambridge IGCSE Coordinated Science (0654) expects you to use the turns ratio, distinguish step-up from step-down transformers, and explain why high-voltage transmission reduces energy loss. This guide links each idea to the calculation and explanation questions examiners set.

Key takeaways

• Transformers work only with alternating current (a.c.) — the field must keep changing.
• Turns ratio: Vp/Vs = Np/Ns (ideal transformer).
• Step-up: more secondary turns → higher secondary voltage.
• Step-down: fewer secondary turns → lower secondary voltage.
• High-voltage transmission reduces I²R heat loss in cables.

What is a transformer in Cambridge IGCSE Coordinated Science?

A transformer has a soft iron core linking a primary coil (input) and a secondary coil (output). Alternating current in the primary produces a changing magnetic flux in the core, inducing an alternating e.m.f. in the secondary. The voltage ratio equals the turns ratio. Step-up transformers increase voltage for efficient long-distance transmission; step-down transformers reduce voltage for safe domestic use.

You can read the full explanation, diagrams and notes on Tutopiya’s Transformer subtopic page before you attempt questions.

Step-up vs step-down transformers

Type	Turns	Voltage	Current (ideal)	Typical use
Step-up	Ns > Np	Vs > Vp	Is < Ip	Power-station → grid
Step-down	Ns < Np	Vs < Vp	Is > Ip	Grid → homes (230 V)

Key transformer equations

Relationship	Formula	Notes
Voltage ratio	Vp/Vs = Np/Ns	N = number of turns
Power (ideal)	Vp × Ip = Vs × Is	100% efficient assumption
Power loss in cables	P = I²R	Lower I → much less loss

Example: primary 100 turns, secondary 500 turns, Vp = 20 V → Vs = 20 × (500/100) = 100 V.

Transformers in past-paper wording

Command word	What the question wants	Typical stem
Calculate	Use turns ratio	”Calculate the secondary voltage.”
Explain	Why high voltage for transmission	”Explain why electricity is transmitted at high voltage.”
State	Transformer requirement	”State the type of current a transformer needs.”
Describe	How a transformer works	”Describe how a step-down transformer reduces voltage.”

Worked exam-style stems

1. “A transformer has 200 primary turns and 800 secondary turns. The primary voltage is 50 V. Calculate the secondary voltage.” Vs = Vp × (Ns/Np) = 50 × (800/200) = 200 V. Reward: correct ratio and answer.
2. “Explain why power stations use step-up transformers before transmission.” Higher voltage means lower current for the same power; less I²R heat loss in cables. Reward: lower current + reduced energy loss.
3. “State why a transformer does not work with d.c.” A steady direct current produces a constant magnetic field — no changing flux, so no induced e.m.f. in the secondary. Reward: no changing flux / needs a.c.

Test yourself with the Transformer quiz once you can calculate voltages and explain power transmission.

How transformers connect to the syllabus

Transformers apply Electromagnetic Induction and follow electricity generated by an A.C. Generator. The Cambridge IGCSE Coordinated Science resource hub links every Electromagnetic Effects subtopic.

Common mistakes students make

• Using transformers with d.c. (they require a.c.).
• Inverting the turns ratio (Vp/Vs = Np/Ns, not Vs/Vp = Np/Ns wrongly applied).
• Saying high voltage increases energy loss in cables (it reduces current and I²R loss).
• Forgetting the iron core links the coils (not air alone in standard diagrams).
• Confusing step-up (more secondary turns) with step-down.

When you need more support

If transformer calculation and explanation questions keep costing marks, work through the Transformer quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Are transformers hard in Coordinated Science? Learn the turns ratio, step-up vs step-down, and why high-voltage transmission saves energy — that covers most questions.

Why do transformers need alternating current? The magnetic flux must change continuously to induce an e.m.f. in the secondary coil.

What is a step-down transformer? A transformer with fewer turns on the secondary coil, reducing voltage for safe use in homes.

How do I revise transformers effectively? Practise turns-ratio calculations, explain power transmission, then take the Transformer quiz.

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