Safety and Workplace Practices
The Safety and Workplace Practices domain is the one where a wrong answer can injure someone. It tests electrical safety, protective devices, earthing, PPE, fire response and workshop discipline in an electronics lab.
Rules
- Treat everything as live until proved dead: isolate, lock off and tag, then test with a proven meter.
- Earthing gives a low-resistance fault path so the MCB trips or the fuse blows. Metal enclosures are earthed; the neutral is never used as a substitute earth.
- Fuses and MCBs protect the cable, not the appliance. Choose the next standard rating above the load current, allowing for switch-on surge.
- PPE: insulated gloves and tools, safety glasses when clipping or soldering, fume extraction for flux smoke.
- Class C (CO₂) or dry powder extinguisher for electrical fires - never water.
- Electric shock first aid: switch off or separate the casualty with dry insulating material, call for help, check breathing, begin CPR if trained.
- ESD control: wrist strap, grounded mat, conductive bags for boards.
Worked example
A 2000 W heater on a 230 V supply. Current = P/V = 2000/230 = 8.7 A. A 10 A fuse is marginal at switch-on surge, so a 16 A MCB with 2.5 mm² copper cable is selected. If the element short-circuits to the metal body, the earth wire carries the fault current, the MCB trips and the casing never reaches a dangerous voltage. Omitting the earth would leave the body live - that is the mark-losing error.
Traps that cost marks
- Saying water may be used on an electrical fire.
- Selecting a fuse equal to the load current with no surge margin.
- Assuming a switched-off appliance is isolated; the neutral may still be live.