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Physics > P5 - National Grid > Flashcards

P5 - National Grid Flashcards

1
Q

What does the national grid do?

A

Transports electricity across the uk.

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2
Q

Where is most electricity generated from?

A

Power stations.

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3
Q

How do power stations work?

A

They generate loads of heat.
They convert the thermal energy into electrical energy.

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4
Q

What does the amount of electricity depend on?

A

Demand.

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5
Q

How do power stations cope with the sudden surge of demand of electricity?

A

They have spare capacity and run lower than their maximum output.

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6
Q

How can we achieve a high power?

A

By using a high current and a high voltage

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7
Q

What is a drawback of the national grid generating power by using high currents to make high heat?

A

Loads of energy is lost to the surroundings.

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8
Q

What does a step up transformer do?

A

Increases the voltage and decrease the current.

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9
Q

What is a benefit of step up transformers?

A

They minimise the energy lost.

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10
Q

What are the two different types of current?

A

Alternating current
Direct current

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11
Q

When do we get alternating currents?

A

When we use alternating potential difference.

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12
Q

What is an alternating current?

A

A current that keeps changing direction going from pos to neg or neg to pos.

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13
Q

What current is our mains supply?

A

Alternating Current.

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14
Q

How much Hertz and Volts are uk’s main supply?

A

50Hz
240V

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15
Q

What is a direct current?

A

Produced by a direct potential difference which is either positive or negative the entire time.

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16
Q

Where can we find direct current?

A

Phones and calculators

17
Q

What do oscilloscopes do?

A

Display the graph on a monitor for d.c.

18
Q

Where can we find alternating currents?

A

Computers.
Kettles.

19
Q

What 3 different wires are in a cable? What colours are they?

A

Earth wire - Green/Yellow
Live wire - Brown
Neutral wire - Blue

20
Q

What are the wires made of? Why?

A

Copper to conduct electricity.

21
Q

What are wires coated with? Why?

A

Layer of insulated plastic for safety.

22
Q

What does the live wire do?

A

Provides the alternating potential difference.

23
Q

What does the neutral wire do?

A

Completes the circuit by carrying away current.

24
Q

Which wire does electricity flow into and which wire does electricity flow out of?

A

Live
Neutral

25
Q

What does the earth wire do?

A

Prevents the appliance casing from becoming live.

26
Q

How would the appliance casing ever become live?

A

If the live wire came loose and touched the casing.

27
Q

How does the earth wire prevent the appliance casing from becoming live?

A

Provides an alternative pathway for the current to flow away.

28
Q

What volts are the wires at?

A

Live wire - 230v
Neutral wire - 0v
Earth wire - 0v

29
Q

For what 2 reasons could a surge happen?

A

When you turn a appliance on or off.
A fault in the current/appliance.

30
Q

What do fuses and circuit breakers do?

A

Break the circuit when the current gets too high

31
Q

What is the fuse? What is it connected to?

A

A thin piece of wire connected to the live wire.

32
Q

What happens when a surge goes through a fuse?

A

The thin piece of wire heats up and breaks so current can no longer flow through it.

33
Q

Benefit of fuses?

A

Simple
Cheap

34
Q

Downside of fuses?

A

Permanently broken after one surge.
Constantly needs to be replaced.

35
Q

What happens when there is a surge in a circuit breaker?

A

The circuit is turned off.

36
Q

What is double insulation?

A

When an entire appliance is covered in a plastic casing so there’s no exposed metal parts.

37
Q

What is a benefit of using plastic to double insulate?

A

Plastic doesn’t conduct electricity so you can’t get electric shocks.

38
Q

What is a rating of the fuse?

A

The current that will cause the fuse to break the circuit.

Physics (2 decks)

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