Energy

8 energy stores

• kinetic

• thermal

• chemical

• gpe

• elastic potential

• electrostatic

• magnetic

• nuclear

4 transfers of energy

• mechnically

• electrically

• heating

• radiation

principle of conservation of energy

Energy cannot be created or destroyed, but can be stored, transferred and dissipated

when is energy useful?

when it is transferred from one store to a useful store

efficiency equation

efficiency = useful output / total input

energy transfer of ball rolling up a slope

kinetic → gpe mechanically

some is transferred mechanically to thermal energy, then by heating to thermal energy store in surroundings

energy transfer of battery powered toy car

chemical →kinetic electrically

what is thermal radiation

infrared radiation, all objects are continually emitting + absorbing

radiation with hot object

emits more than it absorbs

radiation with cooler object

absorbs more than it emits

what state does conduction occur in, WHY

solids, particles have to collide with each other

what is conduction

the process where vibrating paritcles transfer energy from their kinetic store to the kinetic store of neighbouring particles

conduction practical

1. attach beads at regular intervals along metal bar using wax

2. heat end of metal with no beads

3. as conduction occurs, wax will melt, starting at end closest to bunsen

how does convection work

1. water heats

2. hot water is less dense - more KE

3. less dense water rises

4. water cools and becomes more dense - less ke

5. dense water sinks

what states does convection work in

liquid and gas

convection practical

• potassium permanganate in cold water

• gently heat

• dissolved crystal traces path of convection current

how does insulation prevent conduction

traps air pockets - conduction occurs very slowly

black is

best at absorbing and emitting radiation than white

matt surface is

better at absorbing and emitting radiation than shiny surface

work done is the same as

energy transferred

work done =

force x distance

power is the

rate of work

power =

work done/time taken

KE =

½ mv²

gpe =

mgh

falling object energy transfer

• just before it hits ground, all gpe → KE

• IF IGNORING AIR RESISTANCE

4 non renewable energy

1. coal

2. oil

3. natural gas

4. nuclear fuels

3 characteristics of nonrenewable

• finite

• damage envitonment

• provide most of our energy

how do fossil fuels generate electricity

1. burn fuel

2. heat water

3. steam turns turbine

4. turns generator

3 advantages of fossil fuels

1. lots of fuel, relatively cheap

2. not dependent on weather

3. infrastructure (power stations) already

3 disadvantages of fossil fuels

• emit CO2, contributes to climate change

• coal and oil emit SO2 which causes acid rain

• finite

solar summary + energy transfer

solar cells use light to generate electricity.

solar panels use thermal radiation to heat water

thermal → electrical

advantages of solar

• no CO2

disadvantages of solar

• lots of space - not efficient

• weather dependent - not reliable

wind summary + energy transfer

wind turns turbine

kinetic → electrical

advantages of wind

• no CO2

• land can be used for farming

disadvantages of wind

• weather dependent

• noisy/ugly

hydroelectric summary + energy transfer

water stored at height, released to turn turbine

gpe → kinetic → electrical

advantages of hydroelectic

• reliable

• no CO2

diadvantages of hydroelectric

• can flood areas - destroy habitats

tidal summary + energy transfer

• movement of water turns turbines

• kinetic → electrical

advantages of tidal

• reliable

• no CO2

disadvantages of tidal

• very few suitable locations

• environmental damage

geothermal summary + energy transfer

hot rocks underground are used to heat water

thermal → kinetic → electrical

advantages of geothermal

• reliable

  • little land use

disadvantages of geothermal

• harmful gases

• not many suitable locations

biofuels summary + energy transfer

plant matter, ethanol and methane used instead of ff

chemical → thermal → kinetic → electrical

water wave summary + transfer

• moving water due to waves turn turbines to generate electricity

• kinetic → electrical

nuclear summary + energy transfer

nuclear reactions heat steam, turns turbine

chemical → thermal → kinetic → electrical

advantages of biofuels

carbon neutral

lots of it

advantages of waves for electricity

no co2

renewable

advantages of nuclear

reliable

no co2

disadvantages of biofuels

• lots of land

• uses resources needed for food production

disadvantages of waves

• expensive

• scalability

disadvantages of nulear

dangerous radioactive waste