Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Electricity - Mains > Flashcards

Electricity - Mains Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What purpose does the live wire serve in a plug?

A 
Provides the energy to the device
Potential difference (voltage) = 230V
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What colour is the live wire in a plug?

A

Brown

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

What does the neutral wire in a plug do?

A 
Completes the circuit
Potential difference (voltage) = 0V
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What colour is the neutral wire?

A

Blue

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

What is the purpose of the earth wire in a plug?

A

If there is a fault and the case “becomes live”, current passes through this wire and to the EARTH, = safety

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

What colour is the earth wire?

A

Yellow and green striped

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

Why were the colours of the wires in a plug chosen?

A

For those who are colour blind as they can differentiate between these three colours more easily.

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

What is direct current?

A

Current that travels in one direction DIRECTLY.

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

What is alternating current?

A

Current that changes direction constantly (goes from positive to negative)

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

Give an example of alternating current within a household.

A

Mains Electricity = in the Plug Sockets

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

What is the potential difference of Alternating Current (2 values)?

A

230V to -230V

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

Explain why the frequency of Mains Electricity is 50Hz.

A

Mains Electricity = Alternating Current

Means the current changes direction 50x in a second

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

Describe the graph of Direct Current.

A

|____
|

Axis’ are set up as above.
‘Y’ axis: Voltage
‘X’ axis: Time
The direct current is then a straight line at a set voltage (e.g. 10V)

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

Describe the graph of an Alternating Current.

A

|___
|

Axis’ are set up as above.
‘Y’ axis: Voltage
‘X’ axis: Time
As the alternating current is constantly changing (going up and down), the line would show a smooth, equally distanced “peak and trough” motion, like a wave.

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

What is copper used for in a plug?

A
  • Wires are made of copper

- Why? - good copper, malleable (flexible), doesn’t spring back

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is copper effective at its job within a plug?

A
  • Wires are made of copper

- Why? - good copper, malleable (flexible), doesn’t spring back

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Give an example of a device that provide direct current.

A
  • Comes from Batteries/Cells

- Moved through phone chargers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why is brass good at its job within a plug?

A
  • The pins (hold the live, earth and neutral wire in place) are made of brass
  • Why? - good conductor (electricity can still pass through), stiff and doesn’t corrode over time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why was stiff plastic chosen to make up the plug’s case?

A
  • Good insulator

- Protective of wires inside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

True or False - The flexible plastic casing on the wires is a BAD insulator.

A

False! - good insulator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the role of tin in a plug?

A
  • Thin wire in a fuse is made of tin

- Why? - low melting point so will easily break if a large current flows through, SAFETY.

23
Q

Why is tin effective at its job within a plug?

A
  • Thin wire in a fuse is made of tin

- Why? - low melting point so will easily break if a large current flows through, SAFETY.

24
Q

What is brass used for in a plug?

A
  • The pins (hold the live, earth and neutral wire in place) are made of brass
  • Why? - good conductor (electricity can still pass through), stiff and doesn’t corrode over time
25
Q

Why is the earth wire effective? Explain how it works.

A

Earth wire - offers an different path for the electricity
If there is a surge of electricity, there will be a lot of resistance in that wire. Electricity chooses the easiest path, so it moves down the earth wire, to avoid electrocution.

26
Q

What does a fuse do in a plug?

A

Breaks circuit if there is a surge in electricity.

27
Q

Which wire is the fuse connected to?

A

The live wire, so it can cut off incoming energy if necessary.

28
Q

What is the National Grid?

A

The series of wires, pylons and substations that move electrical energy from the power station to the homes where it is needed.

29
Q

Give an advantage of DC.

A

Safer than AC

30
Q

Give an advantage of AC.

A

Easy to transport.

31
Q

What is a transformer?

A

A machine that can increase or decrease the voltage when moving alternating current across the National Grid.

32
Q

What do you call a transformer that increases voltage?

A

A step up transformer

33
Q

Why would you want to increase the voltage of AC when transporting it?

A

Easier to transport.

34
Q

What do you call a transformer that decreases the voltage?

A

A step down transformer.

35
Q

Why would you want to decrease the voltage?

A

So it is accessible/can be used in a home

36
Q

Why bother changing the voltage at all in the National Grid?

A

To minimise wasted energy.
If constantly fast, is too much for the home.
If constantly slow, energy is moved too slowly and will not reach homes as quickly.

37
Q

Explain why the wires in a transformer have an outer layer of plastic.

A

So the current in the primary coil cannot pass through to the secondary coil via the iron core, and must travel via magnetic fields.

38
Q

Explain why we use transformers to change the voltage in the National Grid.

A

Because it allows us to control the change in potential difference (using the number of turns in the could on each side)

39
Q

Describe the average diagram of a step up transformer.

A

Iron core - |[]|
Primary coil - wire is wrapped around the first pillar =(((=
Secondary coil - MORE (easy to remember as double) wire is wrapped around the second pillar =((((((=

40
Q

Give a step by step method of how a transformer works.

A
  1. Alternating current is supplied to the primary coil.
  2. This causes an alternating magnetic field.
  3. This field is transferred to the iron core and passes through the secondary coil.
  4. This induces a potential difference in the secondary coil.
41
Q

Give a simple explanation of what a transformer does.

A

Transfers current from the primary to the secondary coil using magnetic fields.

42
Q

Why do we use iron for the core of a transformer?

A

Because it is easily magnetised.

43
Q

What does the iron core do in a transformer?

A

It increases the strength of the alternating magnetic field that started in the primary coil.

44
Q

Why doesn’t a direct current work in a transformer?

A

Because DC would create a constant magnetic field, which is does not induce a potential difference in the secondary coil, but AC does.

45
Q

True or False: Transformers are 100% efficient.

A

False - BUT ASSUME THEY ARE IN THE EXAM!

46
Q

Do electrical fields flow from
A)Positive to Negative
OR
B) Negative to Positive

A

A

47
Q

Define static electricity.

A

When two insulators are rubbed together and electrons are transferred between them.

48
Q

How do you describe if an object is a good or bad insulator or conductor?

A

If electrons can easily pass through an object, the object is a good conductor, but a bad insulator.
If electrons cannot easily pass through an object, the object is a good insulator, but a bad conductor.

49
Q

If you rubbed a piece of plastic on a piece of cloth, both of which are insulators, which item would become positively charged (so would lose electrons)?

A

The piece of plastic.

50
Q

Why does static electricity only occur on insulators?

A

Because insulators are bad conductors so the electrons cannot pass through it easily and remain on the surface of the object.

51
Q

Explain how a Van de Graaff generator works.

A

There is friction between the brush and the rubber band in a Van de Graaff generator. Both the band and the brush have electrons on them, as they are insulators so electrons cannot pass through them.
The brush loses electrons and the rubber band gains them as they rub together.
This means the dome at the top of the generator is positively charged.
The excess electrons taken from the brush are transported back down the rubber band and are transferred back to the rod so they can be earthed, or taken away.

52
Q

Why do the electrons move from the brush to the rubber band in a Van de Graaff generator?

A

The direction the electrons move depends on the objects involved, and it differs depending on the material.
We don’t need to know the specifics of this.

53
Q

Explain why sparking occurs whilst using a Van de Graaff generator.

A

Sparking is the potential difference between a charged and uncharged object.
In a Van de Graaff generator experiment, the charged object is the metal dome and the uncharged object will be the discharge wand that comes with the generator. This causes electrostatic attraction and pulls the two together.
Air is usually an electrical insulator with no charge but when air is near a strong charge, it loses electrons (ionisation) becomes positive. This means that air can briefly conduct and electrons can flow, which is the spark you can see.

Physics (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions