Topic 3 Flashcards
3.5 3.7
3.1
State the equation for GPE
GPE=mgh
3.1
Rearrange the GPE equation to make h the subject
h=GPE/mg
3.1
Rearrange the GPE equation to make g the subject
g=GPE/mh
3.1
Rearrange the GPE equation to make m the subject
m=GPE/gh
3.2
State the equation for KE
1/2m(v²)
3.2
Rearrange the KE equation to make m the subject
m=2KE/v²
3.2
Rearrange the KE equation to make v the subject
v=√2KE/m
3.3
State how energy is transferred in a light bulb
Electrical -> light (useful) & thermal (waste)
3.4
Explain the law of conservation of energy
-E can’t be created or destroyed
-Only stored or transferred
3.5
Describe the energy transfers that take place in a hydroelectric dam
-KE from flowing water -> KE store of turbine -> KE store of generator
-Some dissipated as thermal E
-Transfers electrically to National Grid
3.5
Describe the energy transfers that take place when fossil fuels are burnt for energy (what about nuclear fuels?)
-Chemical store of fuels -> thermal store of water -> KE store of turbine -> KE store of generator
-Electrically to National Grid
-Starts with nuclear energy of fuel, rest same
3.5
Describe the energy changes involved when a ball is projected upwards
Chemical energy from person holding ball -> KE store of ball as moves up -> GPE as h increases
3.5
Describe the energy changes involved when a moving object hits an object. Use a car as an example
-Chemical store in fuel -> KE of car
-KE decrease when hits object
-Most KE dissipates to themal store of surroundings
-Some E transferred mechanically to thermal store of wall (F of car on wall)
-Some dissipated as sound waves
3.5
Describe the energy changes involved when an object is being accelerated by a constant force
Chemical E when stationary -> KE when accelerates
3.5
Describe the energy changes involved when a vehicle is slowing down
-KE when moving
-Dissipated as thermal (due to friction) when decelerates
-Some dissipated as sound waves
3.5
Describe the energy changes involved when water is boiled in an electric kettle
Electrical E from mains supply -> thermal store of heating element in kettle -> thermal store of water
3.5
Describe the energy changes involved when someone is jumping on a trampoline
-KE from jumping person -> EPE of trampoline -> back to KE as bounce up -> GPE as h increases
-Some dissipated to thermal store of surrounding
3.6
When there are energy transfers in a closed system, there is no net change to the total energy. Explain why
-E transfers between stores
-But overall E of system = conserved
3.6
Define the term net change of energy
Overall change to whole system
3.7
When do mechanical processes become wasteful?
-When cause rise in temp
-Dissipated to thermal store of surroundings
3.8
Explain what happens in all system changes
E = dissipated -> stored in less useful ways
3.8
State 4 reasons as to why machines waste energy
-Friction between moving parts
-Air R
-Electrical R
-Noise
3.9/3.12
Explain 2 ways of reducing energy transfers within a system. What does this also do?
Lubrication
-Reduces friction between moving parts
Thermal insulation
Increase efficiency
3.9
How is heat loss from a house reduced by having a cavity wall?
-Air trapped between walls
-Air = bad thermal conductor
3.9
How is heat loss from a house reduced by filling the cavity wall with foam?
Smaller air pockets prevent heat loss through convection currents
3.9
How could a wall be improved to prevent heat loss by radiation?
-Light shiny material on wall
-Radiation reflected
3.10
Define the term thermal conductivity
How well material transfers heat
3.10
Why does an igloo retain heat more compared to a cotton tent
-Snow = good insulator bc has large amount of trapped air
-Air poor thermal conductor
-Reduce heat transfer
-Cotton = bad insulator
-Air easily escapes
3.11
State the equation for efficiency
efficiency = (useful out/total in) × 100
3.11
Rearrange the equation for efficiency to make useful energy out the subject
useful out = (efficiency × total in) /100
3.11
Rearrange the equation for efficiency to make total energy in the subject
total in = useful out × 100/efficiency
(not sure this is right)
3.12
State 2 methods to reduce friction
-Lubrication
-Add bearings to prevent components rubbing together
3.12
How can air resistance be reduced?
Streamline objects
3.13
State 6 examples of renewable sources of energy
-Solar
-Wind
-Bio-fuel
-Hydroelectricity
-Geothermal
-Tidal
3.13
State 2 examples of non-renewable sources of energy
-Fossil fuels (coal, oil, natural gas)
-Nuclear
3.13
Explain how a wind turbine, tidal energy, hydroelectricity and fossil fuels are used to generate electricity
-Wind/water (fossil fuels combusted to heat water -> steam) turns turbine
-Turbine turns generator
-Generator generates electricity
3.13
Explain how nuclear power generates electricity
-Nuclear fuel heats water -> produces steam
-Turns turbine
-Turns generator
-Electricty
3.13
Explain how geothermal energy is used to generate electricity
-Water pumped down to hot rocks
-Returns as steam
-Turns turbine
-Turns generator
-Electricity
3.13
Evaluate the advantages and disadvantages of fossil fuels
Advs
-Reliable
-Energy dense
Dis
-Non-renewable
-GHG & pollution
3.13
Evaluate the advantages and disadvantages of nuclear power
Advs:
-Reliable
-Energy dense
-No GHG
Dis
-Non-renewable
-Produces dangerous radioactive waste, long t to decay
3.13
Evaluate the advantages and disadvantages of bio-fuels
Advs
-Renewable
-CO₂ cancels
Dis
-Takes land, resources needed for food production
3.13
Evaluate the advantages and disadvantages of wind energy
Advs
-Renewable
-No GHG
Dis
-Not reliable
-Noise & visual pollution
-Location restricted
3.13
Evaluate the advantages and disadvantages of hydroelectric energy
Advs
-Renewable
-Reliable
-Energy dense
-No GHG
Dis
-Floods
-Destroy habitats
3.13
Evaluate the advantages and disadvantages of tidal energy
Advs
-Renewable
-Tides = predictable
-Energy dense
Dis
-Location restricted
-Environmental harm to estuaries
-Disrupt shipping
3.13
Evaluate the advantages and disadvantages of geothermal energy
Advs
-Renewable
-Reliable
-Geothermal stations are small
Dis
-Harmful gases from underground
-Location restricted
3.13
Evaluate the advantages and disadvantages of solar energy
Advs
-Renewable
-No GHG
Dis
-Not reliable
-Use lots of land
3.14
Describe 2 trends in the use of energy resources
-Increase in renewable energy & natural gas
-Decrease in coal & nuclear
