An electrical engineer is analyzing the safety design of a high-power domestic heater connected to a 230 V AC mains supply.
The diagram below shows the electrical connection scheme of the heater's circuit.
The mains connection and internal wiring include several safety features.
One of these safety features has been ticked in the table below.
Put two more ticks (✓\checkmark✓) in the table to show the other two safety features of this electrical setup.
| Component of the mains system | Safety feature |
|---|---|
| Heating element | |
| Earth wire | |
| Fuse | |
| Live wire | |
| Insulating outer sheath | ✓\checkmark✓ |