Year 9 Science · Unit 3 · Lesson 14
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Learning Goals
Because… chain
Label each stage of the electricity journey from a power station to your home. Fill in the empty cells to describe what happens at each step.
Key reason high voltage is used for long-distance transmission:
Real-world context
A large solar farm in outback South Australia generates electricity that must travel approximately 800 km to reach Adelaide. Engineers calculated that without transformers, approximately 60% of the power would be lost as heat in the wires. Using step-up transformers to raise the voltage to 275 kV before transmission, the actual power loss is reduced to around 3%. This principle underlies billions of dollars of new transmission infrastructure proposed in Australia's Integrated System Plan (AEMO, 2024).
(a) Using the formula P_loss = I²R, explain why lowering the current (by raising the voltage) results in much less power being lost as heat in the wires.
(b) What is the role of the step-up transformer at the solar farm and the step-down transformer near Adelaide? Why are BOTH needed?
(c) Why does this example support the argument that Australia needs to invest more in long-distance transmission infrastructure as it expands renewable energy from remote regions?
1. The NEM covers 5 Australian states and territories spanning about 5,000 km. Why is maintaining exactly 50 Hz frequency across this entire grid essential to its safe operation?
2. Western Australia operates the SWIS (South West Interconnected System) grid separately from the NEM. Suggest ONE geographical reason why this might be the case.
Wrap Up
In one sentence, what was the main idea of this lesson?