Extra TopicsTopic Summary
Topic Summary: National Grid and Transformers
Part of National Grid & Transformers — GCSE Physics
This topic summary covers Topic Summary: National Grid and Transformers within National Grid & Transformers for GCSE Physics. Revise National Grid & Transformers in Extra Topics 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 12 of 12 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 12 of 12
Practice
13 questions
Recall
12 flashcards
Topic Summary: National Grid and Transformers
Key Terms
- National Grid — network distributing electricity nationally
- Transformer — changes AC voltage using electromagnetic induction
- Step-up — increases voltage, decreases current
- Step-down — decreases voltage, increases current
- Turns ratio — ratio of primary to secondary turns = ratio of voltages
Key Equations
- Turns ratio: Vp / Vs = Np / Ns
- Power (ideal): Vp × Ip = Vs × Is
- Power loss in cables: P = I²R
- Power = V × I
National Grid Sequence
- Power station generates at 25,000 V
- Step-up transformer → 275,000–400,000 V
- Transmission via pylons (low current)
- Step-down at substation → 33,000 V
- Further step-down → 230 V for homes
How a Transformer Works
- AC flows in primary coil
- Creates changing magnetic field
- Iron core transfers field to secondary
- Changing field induces voltage in secondary
- Ratio of voltages = ratio of turns