Electrical Safety
What this domain tests
Electrical Safety checks whether you can work on 230 V, 50 Hz domestic and workshop installations without injury: effects of current on the body, isolation and lock-off, PPE, earthing, and response to electrical fire and shock.
Core rules
- Treat every conductor as live until it is isolated, locked, tagged and proved dead with a tester whose function you have checked.
- Typical 50 Hz current effects: about 1 mA is felt, 10–15 mA causes “let-go” difficulty, 30 mA can disturb breathing, and 50–100 mA across the heart can cause ventricular fibrillation. This is why 30 mA RCCB protection is used for socket circuits.
- Wear ISI-marked insulating gloves, use 1000 V insulated tools, wear safety shoes, and remove watches, rings and metal chains.
- Isolate in order: inform the user, switch off, lock and tag, test for dead, discharge capacitors, and earth the circuit where required.
- Use CO₂ or dry-powder extinguishers on live electrical fires; never water. For a shock victim, switch off the supply before touching the person.
Worked example
A worker contacts a 230 V live part. If body resistance is about 1,000 Ω, Ohm’s law gives I = 230 ÷ 1,000 = 0.23 A = 230 mA. That is well above the fibrillation threshold, so the shock is lethal. Dry insulating gloves raise resistance and reduce current, but isolation remains the primary control.
Traps that cost marks
Assuming neutral is safe; using a tester without proving it on a known live source; working alone; using water on an electrical fire; and touching a casualty before the supply is isolated.