A power station generates electricity at a potential difference of 25 kV25\ \text{kV}25 kV.
The power transmitted through the national grid is 50 MW50\ \text{MW}50 MW. The transmission cables have a total resistance of 4.0 Ω.
The electricity is transmitted at 400 kV400\ \text{kV}400 kV.
Calculate the current in the transmission cables.
Calculate the power wasted heating the transmission cables when the electricity is transmitted at 400 kV400\ \text{kV}400 kV.
Show that transmitting the same power at 25 kV25\ \text{kV}25 kV instead of 400 kV400\ \text{kV}400 kV would increase the power wasted in the cables by a factor of 256.
A step-up transformer increases the potential difference from 25 kV25\ \text{kV}25 kV to 400 kV400\ \text{kV}400 kV. The primary coil has 1200 turns.
Calculate the number of turns on the secondary coil.
Use the Equation Sheet.
16 exam-style questions on OCR GCSE Physics 8.2 Powering Earth, covering 8.2.1 Renewable and non-renewable energy resources, 8.2.2 Patterns and trends in energy use, 8.2.3 The national grid, 8.2.4 Step-up and step-down transformers, 8.2.5 Efficiency of the national grid, 8.2.6 Transformers and power transmission at high voltage, 8.2.7 The UK domestic supply, 8.2.8 Direct and alternating potential difference, 8.2.9 Live, neutral and earth wires, and 8.2.10 Dangers of mains electricity. Each one has a worked solution and a mark scheme showing where the marks go.