electricity - domestic electricity Flashcards
cables and plugs, electrical safety devices
domestic electricity - electricity entering the house
electricity entering the house first passes through the consumer unit (fuse box and meter)
the sockets on each floor are usually arranged in a loop
separate spurs link some fittings to the mains so they can be isolated
this is a ring circuit and it is also used for lighting circuits
what do we use to connect appliances to the mains electricity supply
a three pin plug
what connects the plug to the appliance
a length of flex that is made of three smaller wires, which are colour coded
what are the three wires and their colours
earth - green and yellow
neutral - blue
live - brown
what is the purpose of the earth wire
carries excess charge away from metal parts
it is the longest wire
it connects the metal casing to the ground
what is the purpose of the neutral wire
completes the circuit - without this it won’t work
what is the purpose of the live wire
carries current to the circuit - if current is too strong it will blow
why are thicker wires used to carry larger currents
the larger current will transfer more thermal energy and thicker copper stands will reduce the resistance (reducing energy loss) and a thicker plastic casing will keep the user safe
what are the inner stands of the wire made of and why
copper as it is a very good conductor of electricity and very ductile
what are the plug pins made of and why
brass as it is an alloy and it is stronger than copper
what is the outer casing of the flex and plug made of and why
plastic as it insulates each wire so current cannot move from one to another
it also protects the user from electric shock
about double insulation
double insulated appliances:
- do not need an earth wire
–> because there are no exposed metal parts so no chance of the casing becoming live
- double insulated appliances are represented by a square in a square
all about fuses
- a fuse is a thin wire
- when current is too high, the fuse wire will get too hot and melt, breaking the circuit
- fuses come rated 1A, 3A, 5A etc (to select the right fuse, check the current of the appliance and choose the next one up)
a fuse too low - will blow every use
a fuse too high - never melt before danger gets too great
all about residual current circuit breakers (RCCB)
- an RCCB will break a circuit if it detects a slight difference in current between live and neutral wires
- better than fuses as they respond faster and can be reset at the touch a button
- circuit breakers can be bought to fit onto any plug or they can be installed into a modern fuse box
