4.2.4.3 The National Grid

Question 1

The National Grid:

Answer 1

a system of high voltage cables and transformers linking power stations to consumers

Question 2

What is the national grid used to do?

Answer 2

electrical power is transferred from power stations to consumers using the National Grid

Question 3

What are step-up transformers used to do?

Answer 3

• step-up transformers are used to increase the potential difference from the power station to the transmission cables
• less energy is lost in the power cables when the potential difference is high
• as the power is constant (P = IV) current decreases so less energy is lost

Question 4

Why are step-up transformers used?

Answer 4

• energy is always lost in the power cables due to the resistance of the wire
• can reduce this energy loss by building power stations near homes - but people don’t want to live near power cables
• step-up transformers are used to increase the potential difference from the power station to the transmission cables - less energy is lot in the power cables when the potential difference is high

Question 5

What are step-down transformers used to do?

Answer 5

• step-down transformers are used to decrease, to a much lower value, the potential difference for domestic use
• National Grid to consumers
• for consumer safety

Question 6

Why is the National Grid an efficient way to transfer energy?

Answer 6

• a low resistance and a low current mean that the transmission wires will not heat up as much
• as a result, most of the power is delivered to the consumer, and not lost through the wires
• The National Grid has very high powers, meaning very high currents and voltages
  
  • high potential difference means low current (less energy dissipated) for the same power
  • during transport, we can boost the voltage very high and make the current very low, but still maintain the same power
    - increases efficiency of power transmission