Energy Flashcards
Power equation
Time taken
What is power measured in
Watts
Work done =
Force (n) x distance moved (m) in direction of the force
Change in GPE (joules )
= weight x change in veritical height
Kinetic energy
0.5 x mass x speed squared
What happens when an object is moved by a force
The force does work and energy is transferred
If an object travels faster it’s kinetic energy …
Increases
The bigger an objects mass
The bigger the kinetic energy
Convection takes place in …
Liquids and gasses
Why does convection happen
When liquids or gases are heated the particles gain kinetic energy and move around so take up more space which means the density of the hot liquid or gas is less than the cool liquid or gas on top of it. This leads to the hot liquid or gas rising . Cold liquid or gas is drawn into replace the liquid or gas that has risen and is in turn heated :
Why does conduction take place
When heat is transferred by particles vibrating more and making neighbouring particles move more
What are the best and worst conductors
Solids are the best and gases are the worst but are the best insulator
What can thermal radiation do
It’s an electromagnetic wave so can travel through a vacuum as it does not need particles
Silvered surfaces are
Good reflectors and bad absorbers / emitters of heat radiation
Black surfaces are
Good emitters and absorbers of infra red radiation but bad reflectors
What happens when a metal is heated
The electrons move faster and spread throughout the metal and collide with other electrons transferring their energy
How can we reduce heat loss
Wasted heat energy wastes money we can use insulators to stop heat energy escaping like trapped air e.g in expanded polystyrene or between the fibres of a wily jumper . Shiny silver surfaces help to reduce heat loss by radiation
What can we put on windows and in walls to stop heat loss
Double glazing and cavity wall insulation
Why is water a por conductor of heat
Particles are too far apart to pass the heat energy quickly
Efficiency equation
Useful energy output
——————– x100
Total energy input
A clockwork motor contains
Stored mechanical energy which is turned into kinetic energy when the spring unwinds
An electric generator turns
Kinetic energy into electrical energy
A rollercoaster free rolling down turns
Potential energy into kinetic energy
What can stored energy be turned into
Active energy
What is a non renewable energy source
Can’t be replaced and will eventually run out and A renewable slice is replaced naturally
Wind energy
Wind mills convert kinetic energy if the wind into electrical energy by using wind to turn generator
It’s renewable but very expensive to set up and few areas r suitable
Hydroelectric power
GPE water stored at height at reservoirs and mountain lakes , water gains kinetic energy falling down the hill , water drives turbine which kinetic energy is y into electrical energy by a generator renewable but few area of world suitable can spoil landscape and alter natural habitat
Tidal energy
Dam built across estuary harnesses kinetic energy of sea , fast flowing water turns generators as the tide comes in its renewable but expensive to set up and few places in the world are suitable . As tide falls water flows out of estuary and turbines are spun again damages habitats for wildlife
Solar power
Light from sun converted into energy by photovoltaic cells or is used as a heat source . Renewable no CO2 but requires continuous sunshine and cell does not produce a lot of electricity needs bright sunlight and expensive
Nuclear energy
Radioactive materials naturally release heat its non renewable and radioactive waste is hard to store and small amounts of nuclear fuel gives large amounts of energy
Isotope of uranium needed
Power stations expensive to build
Releases no greenhouse gases
Geothermal energy
Water heated by earths hot rocks can drive turbines to generate electricity or used for domestic heating by being piped to houses its renewable large quantities of energy available but it requires deep drilling and expensive . Also geysers and springs give readily available geothermally heated water
Biomass energy
Plants used to make alchahol which is used as Petrol its renewable but requires huge amounts of land to grow plants
solar heating
Focusing mirrors focus heat radiation can heat water for high pressure steam production which drives turbines which drive geenarator
. Solar heating panels used for water heating absorb thermal radiation
Fossil fuels
Non renewable produces greenhouse gases
What is electricity and how’s it generated
Not an energy resource generated in power stations by this :
Stored energy in form of burning fossil or nuclear energy is used to heat water , heat energy in high pressure steam drives turbine this movement energy of rotating turbine spins generator giving electrical output. Energy .
Why are we searching for alternate energy forms
Demand for fuel and worries about global warming and pollution
Wave energy
Rising water pushes air past turbine spinning turbine drives generator . Falling water sucks air back past turbine making it spin again
Clean eentgy source no greenhouse gases
What do different types of powers station need to be able to do
Need to be able to respond to changes in demand for electricity . Different types differ in speed which they can meet electricity demand which varies sometimes unpredictably . Nuclear power stations can’t be turned on instantly , process of starting reaction and heating up the reactor is lengthy so it can’t meet sudden variations in demand .
Fossil fuels can be started more quickly but still take hours to start producing electricity . Gas fired ones can respond quicker than coal .
Hydroelectric power can respond quickly as they can operate in reverse using surplus electricity to pump water back up to high level reservoirs converting electrical energy into GPE
Wind and tidal power r unpredictable
