P2.4 Using mains electricity safety and the power of electrical appliances

Question 1

What current do cells and batteries supply?

Answer 1

Current that always passes in the same direction, this is called direct current

Question 2

What is an alternating current?

Answer 2

One that is constantly changing direction

Question 3

What is the period of an AC supply?

Answer 3

The time taken for one complete oscillation. You can find the period by looking at the time taken between one peak/trough and the next

Question 4

What is the frequency of an AC supply?

Answer 4

The number of oscillation per second. You can find it by dividing one by the period

Question 5

What is an example of an AC supply?

Answer 5

Mains electricity

Question 6

What frequency does the UK mains electricity have and what voltage?

Answer 6

Frequency of 50 cycle per second (50 hertz) and is about 230 V

Question 7

How are most electrical appliances connected to the mains?

Answer 7

Using cable and a three pin plug

Question 8

How many wires does a cable have?

Answer 8

Two or three

Question 9

What is the core in a cable made of?

Answer 9

Copper, it is good at conducting electricity

Question 10

What are the outer layers made up of?

Answer 10

Flexible plastic, because plastic is a good electrical insulator

Question 11

What is the blue wire?

Answer 11

The neutral wire

Question 12

What is the brown wire?

Answer 12

The live wire

Question 13

What is the green and yellow striped wire?

Answer 13

The earth wire

Question 14

What is the case of a plug made up of?

Answer 14

Tough plastic or rubber, good electrical insulators

Question 15

What are the three pins made up of?

Answer 15

Brass, good electrical conductor

Question 16

What is there between the live terminal and the live pin?

Answer 16

A fuse

Question 17

What is a fuse?

Answer 17

A fuse breaks the circuit if too much current flows

Question 18

What is the cable secured in the plug by?

Answer 18

A cable grip

Question 19

Where does the blue wire go?

Answer 19

The bLue wire goes to the left

Question 20

Where does the brown wire go?

Answer 20

The bRown wire goes to the right

Question 21

Where does the striped wire go?

Answer 21

The sTriped wire goes to the top

Question 22

If an electrical fault causes too great a current, what happens?

Answer 22

The circuit is disconnected by a fuse or a circuit breaker in the live wire

Question 23

When the current in a fuse wire exceeds the rating of the fuse it will…

Answer 23

Melt, breaking the circuit

Question 24

What are some circuits protected by?

Answer 24

Residual Current Circuit Breakers (RCCB)s

Question 25

How do RCCBs operate?

Answer 25

By detecting a difference in the current between the live wire and neutral wires

Question 26

RCCBs operate much...

Answer 26

Faster than a fuse

Question 27

What are appliances with metal cases often?

Answer 27

Earthed

Question 28

Appliances without a earth wire are what instead?

Answer 28

Double insulated

Question 29

What do the earth wire and the fuse do together?

Answer 29

Protect the circuit

Question 30

What are the most common fuse ratings?

Answer 30

3A, 5A and 13A

Question 31

The thicker the wire in the fuse...

Answer 31

The higher the fuses rating

Question 32

What happens when an electrical charge flows through a resistor?

Answer 32

It gets hot

Question 33

A lot of energy is lost in filament bulbs by...

Answer 33

Heating

Question 34

Less energy is wasted in power saving lamps such as...

Answer 34

Compact Fluorescent Lamps (CFLs)

Question 35

What is power?

Answer 35

The rate at which energy is transferred by an appliance

Question 36

What is the equation for power?

Answer 36

E P = ----- t

Question 37

What is power measured in?

Answer 37

Watts

Question 38

What does the P stand for?

Answer 38

Power

Question 39

What does the E stand for?

Answer 39

Energy

Question 40

What does the t stand for?

Answer 40

Time

Question 41

What is the equation for power, potential difference and current?

Answer 41

P = I x V

Question 42

What does the I stand for?

Answer 42

Current

Question 43

What does the V stand for?

Answer 43

Potential difference

Question 44

What is current measured in?

Answer 44

Amps

Question 45

What is the potential difference measured in?

Answer 45

Volts

Question 46

Through calculating the current of an appliance what can we determine?

Answer 46

The size of fuse needed

Question 47

What is the equation for energy transferred, potential difference and charge?

Answer 47

E = V x Q

Question 48

What does Q stand for

Answer 48

Charge

Question 49

What is charge measured in?

Answer 49

Coulombs