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Physics 🔭 > P8 Global Challenges > Flashcards

P8 Global Challenges Flashcards

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1
Q

Energy resources can be ____ or _____

A

Renewable
Non renewable

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2
Q

Fossil fuels are _____

A

Non-renewable

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3
Q

How does geothermal energy work?

A

In volcanic regions magma can be used to heat rocks, which causes water in pipes to heat up
This makes steam which rotates a turbine to turn a generator

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4
Q

How do fossil fuels produce electricity?

A

They can be burned to heat water, which creates steam and turns a turbine
When the turbine rotates a generator is turned

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5
Q

Advantages + disadvantages of nuclear energy?

A

Advantages:
No CO2
Reliable
Disadvantages:
Expensive
Radioactive waste remains dangerous for thousands of years

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6
Q

Disadvantages of solar?

A

No electricity at night
Takes up a lot of land

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7
Q

How is electricity generated in a power station?

A

Fuel is burnt
Steam produced
Kinetic energy from steam turns turbine
Turbine turns magnets in generator
This induces pd in stationary coils of generator

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8
Q

Describe + explain energy trend from 1820-1900

A

Energy consumption steady
Biofuels used most
People used wood for heating - readily available + free
No electricity

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9
Q

Describe + explain energy trend 1900 onwards

A

Energy consumption increased dramatically
World population increased
Electricity generation invented
Industrial revolution

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10
Q

Most widely used fuels from 1900 onwards were…
Why was this?

A

Fossil fuels
Easily available, cheap, used in transport

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11
Q

Nuclear power started in the 1960s but remains a small fraction. Why is this?

A

Only harnessed in 1960s
Expensive
Potentially dangerous
Many countries choose not to use it

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12
Q

What do governments need to consider when deciding on which energy sources to use in the future?

A

Cost
Environmental impact
CO2 emissions
How long resource will last

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13
Q

Name top 3 UK electricity sources

A

Gas
Nuclear
Wind

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14
Q

Why has use of coal decreased?

A

Coal produces most CO2 of any fossil fuel so contributes most to climate change

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15
Q

Why has use of renewable energy sources increased?

A

Technology now available
Renewables becoming cheaper
Governments switch to these to reduce greenhouse gas emissions

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16
Q

Why have use of gas and nuclear remained roughly constant?

A

Neither are ideal
Gas produces least CO2 of any fossil fuel
Both provide reliable electricity

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17
Q

Define current

A

Rate of flow of charged particles

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18
Q

Define potential difference

A

Energy per unit charge

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19
Q

What does high current cause?

A

Heat

20
Q

How are transformers used in the national grid?

A

Step-up transformers near power station increase pd
This decreases current, reducing energy losses as heat in wires
Step-down transformers near homes decrease pd back to safe levels

21
Q

How does a transformer work?

A

Alternating pd causes alternating input current in primary coil
Causes alternating magnetic field —> magnetises iron core
Secondary coil experiences alternating magnetic field
Induces pd in secondary coil and therefore alternating output current

22
Q

Why would direct current not work in a transformer?

A

Direct current would create unchanging magnetic field so no pd would be induced

23
Q

What is the value of potential difference used in the UK?

A

230V

24
Q

What is the value of frequency used in the UK?

A

50Hz

25
Q

What are two dangers of electricity?

A

Can cause fires
Can electrocute you

26
Q

What colour is the live wire?

A

Brown

27
Q

What does the live wire do?

A

Carries the high voltage

28
Q

What colour is the earth wire?

A

Yellow + green

29
Q

What does the earth wire do?

A

Safety wire that stops appliance becoming live

30
Q

What colour is the neutral wire?

A

Blue

31
Q

What does the neutral wire do?

A

Completes the circuit

32
Q

What is a fuse?

A

Contains a thin wire
This melts if current is too high
(Breaks circuit)

33
Q

The number on a fuse tells us…

A

The maximum current before they melt

34
Q

How do fuses and earth wires work to keep appliances safe?

A

If there is a fault then appliance could become live
To stop this we have an earth wire which provides a very low resistance path to earth
We get a surge (high) current which melts fuse and breaks circuit

35
Q

How to choose correct fuse?

A

Fuse rating should be slightly above operating current
Eg if current = 6.5A then fuse should be 7A

36
Q

What are the common fuses

A

3A, 5A, 7A or 13A

37
Q

Define braking distance

A

Distance car travels after applying brakes

38
Q

Define thinking distance

A

Distance car travels between driver spotting hazard and applying brakes

39
Q

How do speed cameras work?

A

Takes 2 photos a known time apart
Markers on road used to measure distance
S=d/t

40
Q

Name 3 factors that affect braking distance

A

3 from:
Road surface
Worn brakes
Worn tyres
Mass
Ice/rain
Gradient of road
Speed

41
Q

Name 3 factors that affect thinking distance

A

3 from:
Tiredness
Drugs / alcohol
Speed
Distractions
Old age

42
Q

What is stopping distance

A

Thinking distance + braking distance

43
Q

How are speed and thinking distance linked?

A

As speed increases, thinking distance increases linearly

44
Q

How are speed and braking distance linked?

A

As speed increases, kinetic energy (+ therefore braking distance) increases as a squared relationship (non-linear)

45
Q

High speed or greater mass increases braking distance because…

A

The car has more KE needing to be transferred away from vehicle (more work done)
This takes longer time so car travels further

Physics 🔭 (12 decks)

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