Section 2

Question 1

earth wire

Answer 1

green/yellow

Question 2

neutral wire

Answer 2

blue

Question 3

live wire

Answer 3

brown

Question 4

the live wire voltage

Answer 4

HIGH +VE and -VE voltage (about 230V)

Question 5

the neutral wire voltage

Answer 5

0V

Question 6

what is earthing?

Answer 6

the case is attached to an earth wire

Question 7

double insulation

Answer 7

where an appliance has a plastic casing and no metal parts are showing

Question 8

safety precautions to take when using plugs:

Answer 8

• check the cable isn’t frayed
• check the cables aren’t too long
• check there’s no water near electrical objects
• never push a metal object into a plug socket

Question 9

advantages of circuit breakers

Answer 9

• they can be easily reset
• they operate much faster than fuses which makes them safer
• they work for small current changes

Question 10

what happens when an electric current passes through a resistor?

Answer 10

• there is an energy transfer

- this heats up the resistor

Question 11

what does an increase in temperature do to the resistance of a resistor?

Answer 11

-it increases

Question 12

electrical power

Answer 12

the rate at which an appliance transfers energy

Question 13

current

Answer 13

the rate of flow of charge round the circuit

Question 14

voltage

Answer 14

the driving force that pushes the current around

Question 15

what decides how big the current is?

Answer 15

the voltage and resistance

Question 16

what current is the UK mains electricity?

Answer 16

alternating current

Question 17

what current are batteries supplied with?

Answer 17

direct current

Question 18

what happens to the resistance of a light dependent resistor when the light is brighter?

Answer 18

the resistance falls

Question 19

what happens to the resistance of a thermistor when the temperature increases?

Answer 19

the resistance falls

Question 20

polythene when rubbed

Answer 20

negative

Question 21

acetate when rubbed

Answer 21

positive

Question 22

how to demonstrate electrostatic charge

Answer 22

• with a gold-leaf electroscope

- suspend a charged rod

Question 23

inkjet printer

Answer 23

• droplets of ink are charged
• deflected as they pass through two metal plates
• attracted to the oppositely charged plate
• the size and direction of the voltage across each plate changes

Question 24

photocopier

Answer 24

• image plate is positively charged
• white bits of the photocopied image make light fall on the plate and the charge leaks away in those places
• the charged bits attract charged black powder
• this is transfered to positively charged paper
• it is heated so the powder sticks to the paper

Question 25

clothing crackles

Answer 25

static charges are left on your body and the clothes

Question 26

lightning

Answer 26

rain drops and ice bump together inside storm clouds, knocking off electrons and leaving the top of the cloud positively charged and the bottom of the cloud negatively charged. This creates a huge voltage and a big spark

Question 27

fuel-filling

Answer 27

• fuel flows out of a filler pipe and static can build up

- this can easily lead to a spark and an explosion

Question 28

how to solve the fuel-filling problem

Answer 28

• make the nozzles out of metal so that the charge is conducted away, instead of building up
• earthing straps are put between the fuel tank and the fuel pipe