MEPX
Chapter 8 of 10All chapters
  1. 1Charge and current
  2. 2Voltage
  3. 3Resistance and Ohm law
  4. 4Series and parallel
  5. 5Power and energy
  6. 6Components
  7. 7AC and DC
  8. 8Electrical safety
  9. 9Reading a circuit diagram
  10. 10Everyday electricity

Chapter 8 of 10

Electrical safety

What actually hurts people.

Current, not voltage

Current through the body causes harm, and it takes surprisingly little. Skin resistance is what usually protects you, and it falls sharply when wet.

  • Never work on live mains: isolate and verify before touching.
  • Water and electricity together remove the main protection you have.

Protective devices

A fuse or breaker protects the wiring from overload. An earth wire gives fault current a path away from you, and a residual current device cuts power in milliseconds when the two sides do not balance.