Unit 4- Mains Electricity

Question 1

What does the brown wire do

Answer 1

Delivers the energy to the thing it is powering

Question 2

What does the blue wire do

Answer 2

The blue wire takes the electrons away with no energy

Question 3

What does the earth wire do

Answer 3

99.9% of the time it is pointless. But that 0.1% of the time it is used when the power station sends to much energy and the yellow and green wire takes the energy in the ground and absorbs it. The earth wire is just a safety feather

Question 4

What is the danger of spilt drink on heater

Answer 4

It is an electrical conductor, it will start a fire or electrocute you (connects the person to the electricity)

Question 5

What is the danger of lots of plugs in a sockets

Answer 5

Overheats which leads to fire (overload)

Question 6

What is the danger of pulled wire

Answer 6

Could damage the connection inside the wire

Question 7

What is the danger of frayed cable

Answer 7

You are exposing the wire, you could get electrocuted

Question 8

What is the danger of pushing metal objects into electrical socket

Answer 8

You could get electrocuted

Question 9

What is the danger of long cable

Answer 9

It is a trip hazard

Question 10

High energy transfer=

Answer 10

High power

Question 11

What does current cause

Answer 11

Heat in the wires and components

Question 12

What is needed when heat is produced

Answer 12

More voltage is needed to transfer energy to the components

Question 13

Power (P) =

Answer 13

Current (I) ❌ voltage (V)

Question 14

What is power measured in

Answer 14

Watts

Question 15

What is current measures in

Answer 15

Amps

Question 16

What is voltage measured in

Answer 16

Volts

Question 17

Energy (E) =

Answer 17

Power (P) ❌ Time (T) or current (I) ❌ voltage (V) ❌ time (T)

Question 18

What is energy measured in

Answer 18

Joules

Question 19

What power measured in

Answer 19

Watts

Question 20

What is time measured in

Answer 20

Seconds

Question 21

What are the three different colour wires in a plug and what are they all called

Answer 21

Blue: neutral
Brown: live
Green/ yellow: Earth

Question 22

What is the job of the fuse

Answer 22

Protects circuit from damage if current is high or if it has overheated

Question 23

How does the fuse protect the circuit from damage

Answer 23

Thin fuse wire melts ➡️ break in the circuit

Question 24

Can you reset the fuse

Answer 24

No, need to replace the fuse

Question 25

It the fuse effective

Answer 25

It is slow, circuit breaks slowly

Question 26

What is the job of the RCCB

Answer 26

Protects circuit from damage if current is high or if it has overheated

Question 27

How does the RCCB protect the circuit from damage

Answer 27

Switch open ➡️ breaks circuit

Question 28

Can you reset the RCCB

Answer 28

Yes, you have to close it

Question 29

Is the RCCB effective

Answer 29

It is fast, the circuit breaks instantly

Question 30

Voltage variation of the line terminal

Answer 30

The voltage of the live terminal varies sinusoidally between +325 and -325 taking 1/50 or 0.02 second to complete one cycle

Question 31

What are the danger of mains electricity

Answer 31

1. Fire :
   This can be caused by too high current flowing along cables or through appliances
   A fuse or circuit breaker is used to limit the current to a safe level
2. Electrocution :
   This can occur when contact is made with the live wire. Death can occur if a current above 100ma (0.1A) flows through the body
   The earth wire in combination with a fuse or circuit breaker can prevent electrocution

Question 32

What is a fuse?

Answer 32

A fuse is a length of wire designed to melt and so breaking a circuit when the current passes through it goes above a certain level.

The fuse rating must be slightly higher than the normal current so it melts in a surge and protects from shock.