Keywords: Conduction, convection, radiation, kinetic, gravitational, chemical, elastic
Conduction-energy is transferred via
particles colliding. It happens quicker Travel as waves, known as
in solids due to particles being close thermal/infra red radiation. The
together. It is quick in metals as heat from the sun
electrons are free to move
reaches us in this way,
the waves can travel through a
Convection- Liquids and gases expand when they are heated. The particles
move faster and the gap between particles widens. The liquid or gas in hot
areas is less dense than the liquid or gas in cold areas, so it rises into the cold
areas. The denser cold liquid or gas falls into the warm areas. In this way, Emitters of radiation
convection currents are set up
Heat Heat moves White/silver surfaces emit less
thermal radiation. Polar bears are
Types of Energy white so they emit less thermal
-Gravitational Potential (objects above the
Earths surface have this)
Reducing Heat Loss Examples
-Flasks have a vaccum layer so
-Kinetic (moving) conduction and convection don’t
Energy Efficiency -Silver materials used so less
-Elastic (stretched or compressed objects)
Efficiency = useful energy out thermal radiation emitted.
total energy in -Larger objects have a smaller
-Nuclear surface area : volume ratio so less
To convert to a percentage x 100! heat is lost.
The Energy Law
Energy can’t be created or destroyed it is just -Loft insulation as hot air rises
Electrical Light 15J(useful) (convection)
transferred into different forms. It is measured in
Joules (J) 20J Heat 5J (wasted) -Double glazing has a layer of air as
conduction is slower in gases.
Efficiency = 15
Electrical Heat (useful)
Keywords: Efficiency, power, joule, nuclear, geothermal. Greenhouse effect, thermal, vacuum, renewable, turbine, generator.
Power Electricity Costs Fossil Fuels
Coal (highest start up time), oil and gas
Power (W)= energy (J) Measured in kilowatt-hours (kWh) the cost per unit also
(shortest start up time). Disadvantages
needs to be known.
time (s) -Carbon dioxide produced –global warming
Energy used (kWh) = power (kW) x time (hours) -Sulphur dioxide produced (acid rain)
Power is the rate at which
Take care with units!
energy is transferred.
1 watt means 1 joule of
energy is transferred every
Chemical reactions involving uranium and
Advantages – no Greenhouse gases produced,
second. plutonium release heat which is used to
renewable, no fuel costs
boil water in power stations.
Disadvantages – noise and visual pollution, won’t
Advantages – no Greenhouse gases
Disadvantages – non renewable,
hazardous waste produced
which must be dealt with.
Cold water is heated using rocks within the
Earth, the resulting steam is used to drive
Water (tidal, wave & hydroelectric) turbines.
The movement of water is used to drive Advantages – renewable, no fuel costs, no
turbines. harmful gases
Advantages – no Greenhouse gases Disadvantages – very few suitable sites.
produced, renewable, hydroelectric and
Electricity and The National Grid tidal are reliable
1- Fuel is burnt to heat water to make steam Disadvantages – can only be used in
certain locations, loss of habitats and Dark colours absorb more heat.
2- The steam is used to spin a turbine farmland. Light colours reflect more heat
3-The spinning turbine spins a generator which produces
4- The electricity goes to transformers to produce the Solar cells convert light into electricity.
correct voltage Solar panels are used to heat water
Step up transformers increase the voltage, step down Advantages – renewable, no fuel costs,
transformers reduce voltage. The National Grid carries no harmful gases produced
energy at a low current as this means less energy is lost as Extra Notes
heat, but it requires a high voltage. Disadvantages – expensive and
inefficient, need a sunny climate, won’t
work at night.