4 Energy resources and energy transfers Flashcards
Energy Stores
- Chemical
- Kinetic
- Gravitational
- Elastic
- Thermal
- Magnetic
- Electrostatic
- Nuclear
Energy Transfers
- Mechanically
- Electrically
- By heating
- By radiation (light, sound)
Principle of the conservation of energy
Energy cannot be created or destroyed, but can be transferred from one store to another
Equation for efficiency
useful energy output/total energy input
x 100
How can thermal energy transfer occur?
- Conduction
- Convection
- Radiation
Conduction
Transfer of thermal energy (heat) through the vibrations of atoms in a solid
Convection
Transfer of thermal energy (heat) through fluids (liquids or gases) by the upwards movement of warmer less dense regions of fluid
Convectional Current
- Air is heated
- So it expands
- So becomes less dense
- So the air rises
Radiation
- Transfer of thermal energy (heat) through infrared waves (IR)
- IR waves can travel in a vacuum (at the speed of light)
Why can conduction only occur in solids?
The particles are packed tightly together, so energy can be transferred from one particle to another
How do IR waves travel?
- Travels in straight lines
- Falls upon objects
What are conductors in relation to insulators?
Best conductors = Worst insulators
Worst conductors = Best insulators
Order of States of Matter from Best -> Worst Conductor / Worst insulator -> Best Insulator
- Metallic Solids
- Liquids
- Gases
Why are gases bad conductors?
There is no bonding between the particles so heat cannot be transferred from one particle to the other
What are absorbers in relation to emitters?
- Good absorbers = good emittors
- Bad absorbers = bad emittors
Order of States of Matter from Good absorbers + emittors -> bad absorbers + emittors
- Dull black
- White
- Shiny silver (good reflector)
Are good reflectors bad absorbers + emittors?
Yes
How does heat travel?
Hot -> Cold
Investigating Conduction
Conduction ring with bars of differnet metals with drawing pin attached with petroleum jelly
Heated
The metal of the drawing pin that falls off first is the best conductor
Control variable: Size of pins, distance of bars from heat source
Investigating Convection currents in water
- Put a crystal of potassium permanganate in the middle of a beaker of water
- Heat gently
- Observe spread of purple
Investigating Convection currents in gases
- Box with 2 chimneys, with lit candle under 1 chimney
- Air warms up, floats up the chimney, and cold air is drawn into the other chimeny.
Investigating how well different objects radiate heat
- Light bulb, half painted black, and half painted shiny white
- Thermometers on either side
- Greater temp. rise on black side, so black is a better radiator of heat
Ways of reducing unwanted energy transfer
- Clothes
- Silver foil blanket
- Energy efficient homes
Reducing unwanted heat transfer: Clothes
- Trap air, which is a bad conductor of heat/good insulator
Reducing unwanted heat transfer: Silver foil blanket
- Inside surface reflects heat back to person
- Outside surface is a bad emittor
Reducing unwanted heat transfer: Silver foil blanket
- Inside surface reflects heat back to person
- Outside surface is a bad emittor
Reducing unwanted heat transfer: Energy efficient homes
- Insulation - traps air to reduce heat loss, stops formation of convection current
- Double glazing windows - increases greenhouse effect
- Eliminating draughts by fixing windows + doors properly
Work Done
Energy transferred (from one store to the other)
Equation for work done
Work Done = Force x Distance Moved
W = Fd
Equation for Gravitational Potential Energy (GPE)
GPE = mgh
Equation for Kinetic Energy
K.E. = 1/2mv(squared)
Power
- Rate of energy transfer
- Rate of doing work
Equation for Power
- Power = Work done/time taken
- Power = Energy transferred/time taken
What process do radiators do?
Convection
How are radiators designed to help maximise heat transfer by convection?
Have curves to increase surface area
How is electricity generated?
- Energy stored in fossil fuels is used to heat water
- Heat energy in high pressure steam drives a turbine
- Kinetic energy of turbine **spins generator **
- Electrical energy output
Energy transfers involved in the generation of electricity
Chemical -> Thermal -> Kinetic -> Electrical
Renewable
The energy resource will not run out
Non - renewable
The energy resource will run out
Ways of generating electricity
- wind
- water
- geothermal resources
- solar heating systems
- solar cells
- fossil fuels
- nuclear power
Fossil Fuels
- Non - renewable
- Coal, oil, gas
Advantages of Fossil Fuels
- Releases lots of energy, relatively cheaply
- Reliable (not reliant on weather
Disadvantages of Fossil Fuels
- Releases CO2 when burned -> contributes to global warming/climate change
- Burning coal + oil releases sulfur dioxide -> causes acid rain
Nuclear Fuel
Uses nuclear fission of uranium to release heat energy
Advantages of Nuclear Fuel
- Clean -> no greenhouse gases produced
- Reliable
Disadvantages of Nuclear Fuel
- Expensive to build + maintain
- Risks of radioactive material leaks
Geothermal Energy
- Renewable
- Uses thermal energy underground (from radioactive decay)
- Cold water is pumped into the ground, and the steam produced is pumped up
Advantages of Geothermal Energy
- Renewable
- Free
- Clean
Disadvantages of Geothermal Energy
- Expensive to drill deep down
- Can only be built in a few places
Wind Power
- Wind Turbines
- Winds are powered by Sun’s heat energy
Advantages of Wind
- Clean
- Renewable
Disadvantages of Wind
- Ruins landscape
- Noise pollution
- May kill birds
- Expensive to setup/maintain
- Unreliable
Wave Energy
- Uses kinetic energy of waves
Advantages of Wave Energy
- Renewable
- No pollution
Disadvantages of Wave Energy
- Unreliable
Tidal Power
- Tidal barrages = big dams where the river joins the sea
- The movement of tides is caused by the gravitational pull of the Sun and Moon
Advantages of Tidal Power
- No pollution
- Renewable
Disadvantages of Tidal Power
- Damages wildlife habitat
- Ruins landscape
Hydroelectric Power
- Dam built in mountains/valleys
- Rainwater is collected, then released at once
Advantages of Hydroelectric Power
- Renewable
- Clean
Disadvantages of Hydroelectric Power
- Floods the mountains/valleys
- Loss of habitat for wildlife
Types of Solar Heating Systems
- Solar water heating panel
- Solar power
Solar Water Heating Panels
Glass lets heat energy from Sun in, and is absorbed by black pipes -> heats water
Advantages of Solar Water Heating Panels
- Renewable
- Free
Disadvantages of Solar Water Heating Panels
Expensive to setup
Solar Power
Photovoltaic cells transfer light energy -> electric energy
Advantage of Solar Power
- Renewable
Clean
Disadvantage of Solar Power
- Loss of farmland
