electrical safety and hazards Flashcards
what is a live wire
this goes alternately negative and positive, making the current flow backwards and forwards
what is a neutral wire?
this completes the circuit. In many systems, it is kept at zero voltage by the electricity supply company
what is a switch
where is it fitted
Component that can be closed or opened to leave the circuit complete or not. Can stop the flow of current when not complete vice versa.
this is fitted in the live wire. it would work equally well in the neutral, but the wire in the cable would still be live with the switch off.
why can a switch be dangerous?
the wire in the cable would still be live with the switch off, this can be dangerous if, for example, the cable was accidentally cut.
what is an earth wire
this is a wire that prevents shock from touch. connects metal to earth and prevents it from becoming live.
what is double insulation?
some appliances- don’t have an earth. This is because their outer case is made of plastic or any insulating material rather than metal, this insulator acts as an insulation around the wire.
how can damaged insulation be hazardous
contact with the wire (live wire especially) due to gap in the insulation causes electric shock which can cause serious injury or shock.
how can overheating of cables be hazardous
when long extension leads are coiled up, they may overheat. The current warms the wire, but the heat has less area to escape from a tight bundle. This might cause a fire.
how can damp conditions be hazardous
water can conduct a current, so if electrical equipment is wet someone might get electrocuted
how does the fuse protect a circuit
what is it
where is it placed
what does it prevent
how to pick a suitable fuse
A fuse protects a circuit.
Thin piece of wire which overheats and melts if current is too high.
It is placed on the live wire before the switch.
prevents circuit from overheating and catching on fire.
A fuse will have a specific current value (e.g. 13 Amps.) so when choosing a suitable fuse, you must use the one above minimum value but less than maximum value
What does the earth wire do
where is it connected to
the main principle behind it
the earth wire creates a safe route for current to flow through if the live wire touches the casing
The Earth terminal is connected to the metal casing, so in such a case, the current goes through the earth wire instead of causing an electric shock.
A strong current surges through earth wire because it has very low resistance
What does a fuse without an earth wire protect?
the circuit
the cabling for a double-insulated appliance
