P5.1/P5.2 - AC/cables

Question 1

direct current

Answer 1

-electric current in a circuit which flows in 1 direction

Question 2

Alternating current

Answer 2

-electric current in a circuit that rapidly changes direction
-mains electricity supply

Question 3

Mains circuit AC supply

Answer 3

-live wire alternates + and - every cycle

Question 4

neutral wire

Answer 4

-has 0 volts
-blue
-completes circuit so charge can flow

Question 5

step-up transformers

Answer 5

-used at power stations
-transfer to national grid
-increases pd of charge for transmission cables

Question 6

step - down transformers

Answer 6

-used to supply electricity to homes
-decreases pd to make it safer for homes

Question 7

why do we use step up transformer

Answer 7

-increasing pd = less current to transfer same amount of power
-less power loss to wasted energy (resistance)
-more efficient

Question 8

measure frequency of ac supply

Answer 8

1/time taken for 1 cycle

Question 9

three - in plug

Answer 9

has a live
-neutral
and earth pin

Question 10

live wire

Answer 10

-brown in colour
-carried pd from mains

Question 11

earth wire

Answer 11

-yellow and green
-safety wire
-longest pin contacts earth wire in wall
-extra electricity leaves through this to make it safer
-prevents electrocution and case becoming live

Question 12

adaptations of plug

Answer 12

-pins made from brass
-case = electrical insulator
-inside of case prevents wires from touching
-contains fuse

Question 13

adaptations of plug - brass material

Answer 13

• good conductor
  -doesn’t rust

Question 14

adaptations of plug - fuse

Answer 14

-acts as a safety mechanism
-acts between live wire and live pin
-too much current passes = fuse melts + cuts live wire off
-stops circuit = safer

Question 15

short circuits

Answer 15

-wires become loose
-live wire touches neutral wire
-big current passes through
-fuse blows
-cuts current off