A step-up transformer at a power station is 100% efficient.
The potential difference across the primary coil is 25 000 V25\,000\ \text{V}25000 V and the current in the primary coil is 3200 A.
The potential difference across the secondary coil is 400 000 V400\,000\ \text{V}400000 V.
Calculate the current in the secondary coil.
Use the equation
VP×IP=VS×ISV_P \times I_P = V_S \times I_SVP×IP=VS×IS
A student says, 'A step-up transformer increases the power because it increases the potential difference.'
Explain why the student is wrong.
The secondary coil is connected to transmission cables with a total resistance of 5.0 Ω.
Calculate the power wasted in the transmission cables.
The power input to the transformer is 8.0 × 107 W.
Calculate the percentage of this power that is wasted in the transmission cables.
108 exam-style questions on Edexcel GCSE Physics 13.2 Transformers and the National Grid, covering 13.2.1 Transformers and induction, 13.2.2 The transformer turns-ratio equation, 13.2.3 The National Grid, 13.2.4 The transformer power equation, and 13.2.5 Advantages of high-voltage transmission. Each one has a worked solution and a mark scheme showing where the marks go.