This key facts covers Key Facts within National Grid & Transformers for GCSE Physics. Revise National Grid & Transformers in Extra Topics for GCSE Physics with 14 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 7 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
📋 Key Facts
- The National Grid transmits at up to 400,000 V to minimise current and reduce power loss
- Power loss in cables is given by P = I²R — halving current reduces loss by a factor of four
- Transformers work by electromagnetic induction — a changing magnetic field induces a voltage
- Transformers only work with AC (alternating current), not DC
- The soft iron core efficiently transfers the changing magnetic field between coils
- Turns ratio equation: Vp / Vs = Np / Ns
- Power equation (100% efficient): Vp × Ip = Vs × Is
- Step-up: more secondary turns, higher output voltage, lower output current
- Step-down: fewer secondary turns, lower output voltage, higher output current
Practice questions for National Grid & Transformers
What is the function of a step-up transformer in the National Grid?
Explain why electricity is transmitted at high voltage and low current through the National Grid power cables.
Quick recall flashcards
How does a transformer work?
AC in primary creates changing magnetic field → iron core transfers field to secondary → changing field induces voltage in secondary (electromagnetic induction)
What voltage do homes receive?
230 V