# Domestic electricity - Paper 1 Flashcards

## To revise domestic electricity (paper 1)

1
Q

State the typical voltage for mains electricity?

A

230 V

2
Q

State the frequency of mains electricity

A

50 Hz

3
Q

Define a.c.

A

Alternating current, the electrons vibrate backwards and forwards. Mains electricity use a.c.

4
Q

Define d.c.

A

Direct current. Electrons only flow in one direction. This is what we get from batteries

5
Q

What would a.c. look like on an oscilloscope?

A

A wave that alternates positive and negative

6
Q

What does d.c. look like on an oscilloscope.

A

A horizontal line

7
Q

See image

A

Line A is live wire which alternates positive and negative at 230 V

Line B is the neutra lwire which alternates close to 0 V

Time period - each wave is 5 squares horizontally. Each square = 0.005 so T = 5 x 0.005 = 0.025

Frequency = 1 / Time period = 1 / 0.025 = 40 Hz

8
Q

State the names and colours of the 3 wires found inside a cable.

A

Live wire - Brown

Neutral wire - Blue

Earth wire - Green and yellow stripes

9
Q

Which wire can be missing from some appliances? Why?

A

Earth wire, if the appliance is plastic and you cannot get an electric shock from it.

10
Q

State the role of the live wire

A

To carry the alternating potential difference from the supply to the component. the potential difference between the live and the earth is 230 V

11
Q

State the role of the neutral wire

A

The neutral wire will complete the circuit from the component back to the supply. The neutral wire is at or close to 0V

12
Q

State the role of the Earth wire.

A

It is a safety wire to stop an appliance becoming live. the earth wire is at 0V as it only carries a current if there is a fault.

13
Q

State the relationship between power, potential difference and current.

A

Power (W) = potential difference (V) x current (A)

P = VI

14
Q

State the units of power

A

Watts (W)

15
Q

State the units of potential difference

A

Volts (V)

16
Q

State the units of current

A

Amps (A)

17
Q

State the relationship between power, resistance and current.

A

Power = Current2 x resistance

18
Q

State the units for resistance

A

Ohms

19
Q

When using an electrical device what factors affect how much electrical energy it uses?

A
1. Time it is used for
2. The power of the appliance
20
Q

State the equation between energy transferred, power and time

A

Energy transferred (J) = Power (W) x time (s)

21
Q

State the equation between energy transferred, charge and potential difference

A

Energy transferred (J) = Charge (C) x potential difference (V)

E = QV

22
Q

State the parts that make up the national grid

A

Cables, pylons, step up transformers, step down transformers

23
Q

What does a step up transformer do? Why?

A

Increases the potential difference, which decreases the current. this reduced the amount of energy lost os heat so makes them more efficient.

24
Q

What does a step down transformer do? Why?

A

Decreases the potential difference which increases the current. this makes them safer to use within homes

25
Q

What is the casing of a plug made from? Why?

A

Plastic , it is a good insulator and strong

26
Q

What are electrical wires made from? Why?

A

Copper, ductile and a good conductor

27
Q

What are the pins in a plug made from? Why?

A

Brass, its a good conductor but also strong

28
Q

Where is the fuse in a plug?

A

Between the live pin and the live wire

29
Q

What is the role of the fuse?

A

If current gets too high the fuse melts and breaks the circuit, cutting off the live wire

30
Q

What happens when the live wire touches the metal case of an appliance, in terms of the earth wire?

A

The large current surges down the earth wire and the fuse blows