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Electrical safety
Beginner
Fuses, earthing and circuit breakers prevent shock and fire.
Currents above ~10 mA through the body can cause muscle lock, 100 mA can be fatal. Fuses, circuit breakers, earth wires and RCDs protect.
Fuse rated slightly above normal current.
Water lowers body resistance.
In more detail
Electrical safety depends on limiting current, using fuses or circuit breakers, earthing metal parts and insulating conductors. Current above about 30 mA through the body can be dangerous.
Real-world uses
- Residual current devices protect people from electric shock.
- Earthing protects appliances with metal cases.
- Household fuses and circuit breakers cut the supply when the current becomes too large, protecting wiring from overheating.
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Frequently asked questions
Why is current more dangerous than voltage?
The body's heart rhythm is disrupted by current, so the current through the body is the key factor.
What does an RCD do?
It detects an imbalance between live and neutral currents and cuts the power quickly.
Why are fuses rated in amps?
The rating sets the current at which the fuse will melt, so it should match the circuit's expected load.
Related topics in Current Electricity & Circuits
Rectifier circuits · Transistor as a switch and amplifier · Logic gates · Household wiring · Electrolysis · Faraday's laws of electrolysis