electricity - domestic electricity Flashcards

cables and plugs, electrical safety devices

1
Q

explain domestic electricity - electricity entering the house

A

passes through the consumer unit (fuse box and meter)
the sockets 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

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2
Q

what do we use to connect appliances to the mains electricity supply

A

a three pin plug

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3
Q

what connects the plug to the appliance

A

a length of flex that is made of three smaller wires, which are colour coded

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4
Q

what are the three wires and their colours

A

earth - green and yellow
neutral - blue
live - brown

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5
Q

what is the purpose of the earth wire

A

carries excess charge away from metal parts
it is the longest wire
it connects the metal casing to the ground

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6
Q

what is the purpose of the neutral wire

A

completes the circuit - without this it won’t work

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7
Q

what is the purpose of the live wire

A

carries current to the circuit - if current is too strong it will blow

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8
Q

why are thicker wires used to carry larger currents

A

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

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9
Q

what are the inner stands of the wire made of and why

A

copper as it is a very good conductor of electricity and very ductile

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10
Q

what are the plug pins made of and why

A

brass as it is an alloy and it is stronger than copper

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11
Q

what is the outer casing of the flex and plug made of and why

A

plastic as it insulates each wire so current cannot move from one to another
it also protects the user from electric shock

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12
Q

about double insulation

A

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

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13
Q

all about fuses

A
  • 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

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14
Q

all about residual current circuit breakers (RCCB)

A
  • 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
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