National grid
- electrical power is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic use
Step-up transformers
- increases the voltage
- this allows the cables to have a low current (because P = IV)
- this is better than a high current because there is less heat energy is wasted
Step-down transformers
- decreases the voltage from power lines for safe household use
Frequency and voltage of domestic power supply
- 50 Hz
- 230 V
- AC
Direct current
- constant amount, flows the same direction.
Alternating current
- constantly changes direction
Wires
- earth wire: safety wire (O V)
- live wire: carries the potential difference (230 V)
- neutral wire: completes the circuit