P5

Question 1

What is a direct current ?

Answer 1

A current that only has one direction

Question 2

What is an alternating current ?

Answer 2

A current that repeatedly reverses its direction

Question 3

What is the frequency in England ?

Answer 3

50hz

Question 4

When using mains appliances , the electricity is supplied from where ?

Answer 4

Power stations

Question 5

Before electricity gets to homes and buildings what does it go to first ?

Answer 5

National grid

Question 6

What is a step up transformer ?

Answer 6

Used at power stations to transfer electricity to the national grid

Question 7

What is a step down transformer ?

Answer 7

Used to supply electricity from the national grid to consumers

Question 8

What is an earth wire ?

Answer 8

The earth wire provides a path from the case to the ground

Question 9

Why is the earth wire important ?

Answer 9

We need this wire because it helps move current to the ground if something like the live wire touches the metal plating

Question 10

Does an earth wire provide a high or low resistant path , why ?

Answer 10

Provides a low resistant path , so that the current goes through the earth wire instead of a person

Question 11

How many wires does a plug have inside it ?

Answer 11

Earth , live and neutral wire

Question 12

What is the neutral wire ?

Answer 12

Neutral wire completes the circuit , just connects everything together .

Question 13

What colours the earth wire ?

Answer 13

Green and yellow

Question 14

What colour is the neutral wire ?

Answer 14

Blue

Question 15

What is the live wire ?

Answer 15

Carries the current toward the appliance from the plug , can go either way .

Question 16

What colour is the live wire ?

Answer 16

Brown

Question 17

What is a fuse ?

Answer 17

A fuse stops the current from flowing , if the current is too high , the high temperature will melt a thin wire causing the fuse to blow

Question 18

What is the cable grip ?

Answer 18

Holds all the wires together to stop them from becoming loose

Question 19

What is the outer insulator ?

Answer 19

Plastic wrapped around the wires for safety

Question 20

The pins inside of the casing are made of what ?

Answer 20

Brass

Question 21

Why are the pins made of brass ?

Answer 21

Because it is a good conductor

Question 22

Plastic is a good what ?

Answer 22

Electrical insulator

Question 23

What is the equation for the power of an appliance ?

Answer 23

Energy transferred / time

Question 24

For an electrical appliance :

Answer 24

. The current through it is the charge that flows through it each second
. The potential difference across it is the energy transferred to the appliance by each coulomb of charge that passes through it .
. The power supplied to it is the energy transferred to it each second . This is the energy transferred by an electric current every second

Question 26

Energy transfer to the appliance each second =

Answer 26

Power supplied = current x potential difference

Question 27

Domestic appliances are often fitted with one of these different three fuses ?

Answer 27

3A , 5A and 13A

Question 28

What is resistance heating ?

Answer 28

When an electric current passes through a resistor, the power supplied to the resistor heats it . The resistor heats the surroundings , so the energy supplied to it is dissipated to the surroundings .

Question 29

When an electrical appliance is turned on , what is forced through it ?

Answer 29

Electrons

Question 30

What is the equation for charge flow ?

Answer 30

Current x time

Question 31

When a resistor is connected to a battery , what happens ?

Answer 31

Work is done by the battery to make electrons pass through resistor

Question 32

The energy transferred to a resistor , in a given time , can be calculated using either of which equations ?

Answer 32

Energy = charge flow x potential difference Energy = power x time

Question 33

When you use an electric heater , how much energy is transferred from the mains ?

Answer 33

You can work this out if you know its power and how long you use it for

Question 34

Energy transferred from the mains =

Answer 34

Power x time

Question 35

Electrical appliances waste energy because ...

Answer 35

The current in both wires and the components of the appliance has a heating effect due to the resistance of the wires and the components