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Year 11 - Science

The National Grid

Mains electricity

Unit Summary

This unit covers UK domestic a.c. supply, mains wiring safety, energy changes in electrical systems, power ratings, and energy transfer. It explains the National Grid, transformers, energy sources, and calculations for energy changes and power transmission efficiency.

Lesson Summary

You will learn to describe the National Grid and explain why transmission lines use a very high transmission voltage.

Key Notes

  • Power is transferred by electricity from power stations to consumers using the National Grid.
  • Step-up transformers increase the transmission voltage from a power station to the transmission line.
  • Step-down transformers decrease the transmission voltage from a transmission line to the consumer.
  • Transmission lines dissipate some energy by heating (P = I²R).
  • A very high transmission voltage reduces transmission current and the heating of transmission lines.

Vocabulary To Learn

  • National Grid: a high voltage transmission system for getting electricity to where it is needed
  • transmission line: a high voltage cable often seen between electricity pylons
  • step-up transformer: a device that can change lower alternating voltages to higher ones
  • step-down transformer: a device that can change higher alternating voltages to lower ones
  • dissipation: the transfer of energy into the surroundings by heating

Common Mistakes To Avoid

  • The voltage (drop) across power lines is the same as the voltage they transmit.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

Power is transferred by electricity from power stations to consumers using the National Grid. Step-up transformers increase the transmission voltage from a power station to the transmission line.

2. Define this scientific word and use it in context. 'National Grid'

a high voltage transmission system for getting electricity to where it is needed. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: The voltage (drop) across power lines is the same as the voltage they transmit. Correction: Spend time to clarify that the power transmitted depends on the p.d. between the live and neutral wires, and power dissipated depends on the drop in voltage from one end of a live wire to the other.

More Lessons In This Unit

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