Higher Tier: Transformers and the National Grid
Part of Electromagnetic Induction — GCSE Physics
This higher tier covers Higher Tier: Transformers and the National Grid within Electromagnetic Induction for GCSE Physics. Revise Electromagnetic Induction in Magnetism for GCSE Physics with 13 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 11 of 14 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
Topic position
Section 11 of 14
Practice
13 questions
Recall
12 flashcards
🎓 Higher Tier: Transformers and the National Grid
Electromagnetic induction is also the principle behind transformers. An AC current in the primary coil creates a changing magnetic field in the iron core, which induces an AC current in the secondary coil.
Transformer equation: Vₛ/Vₚ = Nₛ/Nₚ (voltage ratio = turns ratio)
Why the National Grid uses high voltage: Electrical power = I × V. To transmit the same power at higher voltage, you need less current. Less current means less energy wasted in the cables (P_waste = I²R). Step-up transformers near power stations increase voltage to 400,000 V; step-down transformers near homes reduce it to 230 V.
Why transformers only work with AC: Transformers require a constantly changing magnetic field to induce a current in the secondary coil. DC creates a constant (non-changing) field — the transformer only responds to the moment DC is switched on/off, not continuously. AC continually changes direction, so the field continuously changes, inducing continuous AC in the secondary coil.