P8 Global Challenges Flashcards
Energy resources can be ____ or _____
Renewable
Non renewable
Fossil fuels are _____
Non-renewable
How does geothermal energy work?
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
How do fossil fuels produce electricity?
They can be burned to heat water, which creates steam and turns a turbine
When the turbine rotates a generator is turned
Advantages + disadvantages of nuclear energy?
Advantages:
No CO2
Reliable
Disadvantages:
Expensive
Radioactive waste remains dangerous for thousands of years
Disadvantages of solar?
No electricity at night
Takes up a lot of land
How is electricity generated in a power station?
Fuel is burnt
Steam produced
Kinetic energy from steam turns turbine
Turbine turns magnets in generator
This induces pd in stationary coils of generator
Describe + explain energy trend from 1820-1900
Energy consumption steady
Biofuels used most
People used wood for heating - readily available + free
No electricity
Describe + explain energy trend 1900 onwards
Energy consumption increased dramatically
World population increased
Electricity generation invented
Industrial revolution
Most widely used fuels from 1900 onwards were…
Why was this?
Fossil fuels
Easily available, cheap, used in transport
Nuclear power started in the 1960s but remains a small fraction. Why is this?
Only harnessed in 1960s
Expensive
Potentially dangerous
Many countries choose not to use it
What do governments need to consider when deciding on which energy sources to use in the future?
Cost
Environmental impact
CO2 emissions
How long resource will last
Name top 3 UK electricity sources
Gas
Nuclear
Wind
Why has use of coal decreased?
Coal produces most CO2 of any fossil fuel so contributes most to climate change
Why has use of renewable energy sources increased?
Technology now available
Renewables becoming cheaper
Governments switch to these to reduce greenhouse gas emissions
Why have use of gas and nuclear remained roughly constant?
Neither are ideal
Gas produces least CO2 of any fossil fuel
Both provide reliable electricity
Define current
Rate of flow of charged particles
Define potential difference
Energy per unit charge
What does high current cause?
Heat
How are transformers used in the national grid?
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
How does a transformer work?
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
Why would direct current not work in a transformer?
Direct current would create unchanging magnetic field so no pd would be induced
What is the value of potential difference used in the UK?
230V
What is the value of frequency used in the UK?
50Hz
What are two dangers of electricity?
Can cause fires
Can electrocute you
What colour is the live wire?
Brown
What does the live wire do?
Carries the high voltage
What colour is the earth wire?
Yellow + green
What does the earth wire do?
Safety wire that stops appliance becoming live
What colour is the neutral wire?
Blue
What does the neutral wire do?
Completes the circuit
What is a fuse?
Contains a thin wire
This melts if current is too high
(Breaks circuit)
The number on a fuse tells us…
The maximum current before they melt
How do fuses and earth wires work to keep appliances safe?
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
How to choose correct fuse?
Fuse rating should be slightly above operating current
Eg if current = 6.5A then fuse should be 7A
What are the common fuses
3A, 5A, 7A or 13A
Define braking distance
Distance car travels after applying brakes
Define thinking distance
Distance car travels between driver spotting hazard and applying brakes
How do speed cameras work?
Takes 2 photos a known time apart
Markers on road used to measure distance
S=d/t
Name 3 factors that affect braking distance
3 from:
Road surface
Worn brakes
Worn tyres
Mass
Ice/rain
Gradient of road
Speed
Name 3 factors that affect thinking distance
3 from:
Tiredness
Drugs / alcohol
Speed
Distractions
Old age
What is stopping distance
Thinking distance + braking distance
How are speed and thinking distance linked?
As speed increases, thinking distance increases linearly
How are speed and braking distance linked?
As speed increases, kinetic energy (+ therefore braking distance) increases as a squared relationship (non-linear)
High speed or greater mass increases braking distance because…
The car has more KE needing to be transferred away from vehicle (more work done)
This takes longer time so car travels further
