Exam Focus — National Grid and Transformers

🎯 Exam Focus — National Grid and Transformers

Examined in Edexcel 1PH0/2 (Paper 2). Edexcel frames transformer questions around context scenarios — industrial power distribution, renewable energy connection, household supply — so be ready to identify step-up/step-down roles from unfamiliar diagrams. The turns ratio calculation (Vp/Vs = Np/Ns) is a higher-tier calculation focus on Edexcel 1PH0/2.

Most Common Question Types

• Explain why the National Grid transmits at high voltage [3-4 marks] — must reference P = I²R and link high V to low I to low power loss
• Calculate secondary voltage or turns using the turns ratio equation [2-3 marks]
• Calculate secondary current using the power equation [2-3 marks]
• Explain how a transformer works [4 marks] — describe AC → changing magnetic field → iron core → induction in secondary
• Identify step-up vs step-down from turns or voltage values [1-2 marks]
• "Suggest" questions (Edexcel): Given an unfamiliar coil ratio, suggest whether it is step-up or step-down and explain its purpose in the grid.

What Examiners Want to See

For "explain why high voltage" questions, a full-mark answer must: (1) state that high voltage means low current, (2) reference P = I²R, (3) state that lower current means less power wasted as heat in the cables. Many students lose marks by only stating "less energy lost" without explaining why via the equation.