11) The National Grid

Electricity Distribution via the National Grid

• The National Grid is a large system of cables and transformers that spans the UK, connecting power stations to consumers (those using electricity).

Electricity Production Meets Demand

• Electricity usage varies throughout the day, requiring power stations to produce enough electricity to meet demand.

• Demand increases during peak times, such as morning wake-ups, after school or work, and when it gets dark or cold.

• Major events (e.g., sporting finals on TV) can also lead to spikes in electricity demand.

• Power stations usually operate below maximum capacity to have spare capacity for unexpected demand or station shutdowns.

• Smaller power stations are kept on standby to quickly meet high demand.

High Potential Difference and Low Current

• To transmit large amounts of power, either high potential difference or high current is needed (P=VI)

• High current leads to significant energy loss due to heating of wires.

• Increasing the potential difference to 400,000 V while keeping the current low reduces energy loss, making transmission more efficient.

Transformers and Potential Difference

• Transformers are used to step up the voltage to 400,000 V for efficient transmission.

• A transformer consists of two coils (primary and secondary) and an iron core. A step-up transformer has more turns on the secondary coil than the primary.

• As potential difference increases in a transformer, the current decreases.

Step-Down Transformers

• At the consumer end, a step-down transformer reduces the voltage to safer levels.

• The power relationship in transformers can be described as:
  Power = Potential Difference × Current

• Transformers are nearly 100% efficient, meaning:
  Primary Coil Power=Secondary Coil Power 

• V_primary × I_primary = V_secondary × I_secondary