8.12 Living with electricity

Question 1

Mains current

Answer 1

Mains current is alternating current (a.c.) It flows backwards and forwards.

Question 2

Hz

Answer 2

the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second.

Question 3

Live or hot or active wire

Answer 3

This goes alternately negative anbd positive, making the current flow backwards and forwards in the circuit.

Question 4

Neutral or cold wire

Answer 4

This completes the circuit. In many systems, it is kept at zero voltage by the electricity supply company.

Question 5

Switch

Answer 5

This is fitted in the live wire. It would work equally well in the neutral, but wire in the cable would stilll be live with the switch off. This would be dangerous if, for example, the cable was accidentaly cut.

Question 6

Fuse

Answer 6

This is a thin piece of wire which overheats and melts if the current is too high. Like the switch, it is placed in the live wire, often as a cartridge. If a fualt develops, and the current gets too high, the fuse blows and breaks the circuit before the cable can overheat and catch fire.

Question 7

Earth or grounded wire

Answer 7

This is a safety wire. It connectsathe metal body of the kettle to earth and stops it from becoming live. If the live wire comes loose and touches the metal body, a current immediately flows to the earth and blows the fuse.

Question 8

Double insulation

Answer 8

Some appliances do not have an earth wire. This is because their outercase is made of plastic rather than metal. The plaswtic acts as an extra layer of insulation around the wires

Question 9

RCDs

Answer 9

For extra safety, circuits may be fitted with a type of beaker called a residual current device (RCD). This compares the currents in the live and neutral wires. If they are not the same, then the current must be flowing to earth- The RCD senses the difference and switches off the current before any harm can be done.

Question 10

Plugs

Answer 10

Plugs are a safe way of connecting appliances to the mains.

Question 11

Electrical hazards

Answer 11

Old frayed wiring, Long extension leads, water in sockets or plugs, Accidentaly cutting cables
If an accident happens, and someone is electrocuted, you must switch off at the socket and pull out the plug before giving any help.