Paper 1 - 2b Domestic Electricity Flashcards

1
Q

State the typical voltage for mains electricity?

A

230 V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

State the frequency of mains electricity

A

50 Hz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define a.c.

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define d.c.

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which pin is the earth wire connected to?

A

The top pin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which pin is the live wire connected to?

A

The bottom right pin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which pin is the neutral wire connected to?

A

The bottom left pin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is the fuse in a plug?

A

Between the live pin and the live wire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does the earth wire work with the fuse?

A

The earth wire is connected to a metal case. When there is an electrical fault, the live wire may also touch the metal case. This creates a parellel circuit. The earth wire has a low resistance. This increases the current drawn from the power supply, which melts the fuse on the live wire. This breaks the circuit and stops the metal device becoming live.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is the wire made of copper?

A

As copper conducts electricity and is ductile.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are pins made of brass?

A

As brass conducts electricity, do not rust and are hard to change shape.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is the plug made of stiff plastic?

A

As it is an insulator and it’s hard to change shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does the cable grip do?

A

It prevents the wires from snapping if tension is applied to the cable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why do some electrical devices not have an earth wire?

A

As they are double insulated

17
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.

18
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

19
Q

State the role of the neutral wire

A

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

20
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.

21
Q

State the relationship between power, potential difference and current.

A

Power = potential difference x current (P = VI)

22
Q

State the units of power

A

Watts (W)

23
Q

State the units of potential difference

A

Volts (V)

24
Q

State the units of current

A

Amperes (A)

25
Q

State the relationship between power, resistance and current.

A

Power = (Current)squared x resistance

26
Q

State the units for resistance

A

Ohms

27
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
28
Q

State the equation between energy transferred, power and time

A

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

29
Q

State the equation between energy transferred, charge and potential difference

A

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

30
Q

State the parts that make up the national grid

A

Cables, step up transformers, step down transformers

31
Q

What does a step up transformer do? Why?

A

Increases the potential difference, which decreases the current. This reduces the amount of energy lost to heat so makes them more efficient.

32
Q

What does a step down transformer do? Why?

A

Decreases the potential difference which increases the current. This makes them safer to use in homes.