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30 Cards in this Set
- Front
- Back
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What an Electric Current.. |
is a flow of Charge round a circuit Current = the rate of flow of charge - electrons carry this charge - they are negatively charged |
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Voltage or Potential difference is what... |
an electrical pressure giving a measure of the energy transferred |
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What is a conventional current ? |
a -ve to a +ve flow |
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What does a alternating current (a.c) do? |
keeps reversing its direction back and fourth, the mains electricity in our home is a.c |
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What is a direct current? |
Always flows in the Same direction, voltage does not vary - the current has a constant value |
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What is Electrical power? |
The Energy Transferred per second |
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How do generators make electricity? |
use something called electromagnetic induction |
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Moving a magnet in a coil of wire.... |
Induces the Voltage = electromagnetic induction |
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If you move the magnet into the coil the voltage and current are induced in the opposite direction... |
of when you move it out of the coil |
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If you want a bigger peak voltage you have to increase 4 things... |
1) The strength of the magnet 2) The area of the coil 3) The number of turns on the coil 4) The speed of movement |
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How do generators work? |
Generate an alternating current - by rotating a magnet or rotating a coil of wire - keeping the magnet fixed Need someone to do the turning - a water wheel. |
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Name the non-renewable energy sources.. |
coal, oil, natural gas, nuclear fuels - eg; uranium and plutonium = will all run out/ damage the environment |
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What are the environmental problems with non-renewable's? |
fossil fuels = add to greenhouse effect, cause global warming burning coal + oil = releases sulfur dioxide, causes acid rain coal mining = mess of landscape oil spills = environmental problems Nuclear power = clean - dangerous to dispose- carries the risk of disaster - Chernobyl |
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How do Nuclear reactors work? |
nuclear fission produces - heat - to make steam - drives the turbines. |
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Renewable energy sources will never run out |
although - unreliable - do damage environment in a less nasty way |
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What is Hydroelectricity.. |
Involves building a big dam or a valley Rain water - caught through turbines Big impact on environment - loss of habitat advantage = immediate response - more water can be let through - more electricity generated |
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Wave Power... |
waves up and down motion = drive the generator. Unreliable- if wind drops/no waves useful for small islands |
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Tidal Barrages.. |
are big dams using the sun and moon's gravity, built across river estuaries - with turbines in them water - through a turbine - reliable energy source |
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Wind Power - lots of little wind turbines |
own generator inside - electricity is generated directly from the wind turning the blades - which turn the generator |
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Solar cells generate electric currents directly from sunlight.. |
a relatively small scale, good and reliable source - cost effective even in cloudy countries. |
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Geothermal energy ... |
only possible in certain places - hot rocks lie near the surface. Water is pumped in pipes down to hot rocks, returns as steam = drive the generator |
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Biomass - natural waste that can be burnt to produce electricity |
the burnt material powers the turbine = producing electricity or sometimes fermented to produce = fuels such as biogas or ethanol carbon neutral - as plants grew to produce the waste for animals - absorbed carbon dioxide - this co2 is re-releases in atmosphere. |
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Issues... |
Set-up costs, set-up time, running/fuel costs, reliability issues, location issues, environmental issues. |
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What is the national grid.. |
a network of pylons that covers the whole of Britain, transmits a huge amount of power |
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What do the transformers do? |
Have to step alternating voltage up at one end for efficient transmission - then bring it back down to a safe/useable level |
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How many coils do transformers have? |
2 coils, a primary coil and a secondary coil = joined with an iron core |
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How is the voltage increased? |
using a step-up transformer - they have more turns on the secondary coil than the primary coil |
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How is the voltage decreased? |
by a step-down transformer - they have more turns of the primary coil then the secondary |
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Problems with transmitting huge amounts of energy.. |
it isn't very efficient- power loses are high. High voltage = risk to people - flying a kite near a power line = fatal Effects on long-term health of living near a power line. |
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You can save money by ... insulating your house |
Loft insulation, hot water tanks, double glazing = payback time |
