+
Related Flashcards
Related Topics
Cards In This Set
| Front | Back |
 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, convection currents are set up |
 Types of energy light, sound, gravitational potential (object above earths surface), electrical, kinetic (moving), elastic (stretched), thermal, nuclear |
 Energy lawEnergy can not be destroyed or created it can only be transferred into different forms. It is measured in Joules (J). Electrical ----------------------------|------- Heat (useful) | |------Light/sound (wasted) |
 Conduction-energy is transferred via particles colliding. It happens quicker in solids due to particles being close together. It is quick in metals as electrons are free to move throughout metal. |
|
Radiation Travel as waves, known as thermal/infra red radiation. The heat from the sunreaches us in this way,the waves can travel through a vacuum.
|
 Emitters of radiationWhite/silver surfaces emit less thermal radiation. Polar bears are white so they emit less thermal radiation. |
|
Energy EfficiencyEfficiency = useful energy out total energy inTo convert to a percentage x 100! Electrical -----
|
Reducing Heat Loss Examples-Flasks have a vaccum layer so conduction and convection don’t occur.-Silver materials used so less thermal radiation emitted.-Larger objects have a smaller surface area : volume ratio so less heat is lost.-Loft insulation as hot air rises (convection)-Double glazing has a layer of air as conduction is slower in gases.
|
|
PowerPower (W)= energy (J) time (s)Power is the rate at whichenergy is transferred.1 watt means 1 joule of energy is transferred everysecond.
|
Electricity and The National Grid1- Fuel is burnt to heat water to make steam2- The steam is used to spin a turbine3-The spinning turbine spins a generator which produces electricity.4- The electricity goes to transformers to produce the correct voltageStep up transformers increase the voltage, step down transformers reduce voltage. The National Grid carries energy at a low current as this means less energy is lost as heat, but it requires a high voltage.
|
|
Electricity CostsMeasured in kilowatt-hours (kWh) the cost per unit also needs to be known.Energy used (kWh) = power (kW) x time (hours)Take care with units!
|
NuclearChemical reactions involving uranium and plutonium release heat which is used to boil water in power stations.Advantages – no Greenhouse gases producedDisadvantages – non renewable, hazardous waste producedwhich must be dealt with.
|
|
Water (tidal, wave & hydroelectric)The movement of water is used to drive turbines.Advantages – no Greenhouse gases produced, renewable, hydroelectric and tidal are reliableDisadvantages – can only be used in certain locations, loss of habitats and farmland.
|
 SolarSolar cells convert light into electricity. Solar panels are used to heat waterAdvantages – renewable, no fuel costs, no harmful gases producedDisadvantages – expensive and inefficient, need a sunny climate, won’t work at night. |
 Fossil FuelsCoal (highest start up time), oil and gas (shortest start up time). Disadvantages-Carbon dioxide produced –global warming-Sulphur dioxide produced (acid rain)-Non renewable |
WindAdvantages – no Greenhouse gases produced, renewable, no fuel costsDisadvantages – noise and visual pollution, won’t always work
|
 GeothermalCold water is heated using rocks within the Earth, the resulting steam is used to drive turbines.Advantages – renewable, no fuel costs, no harmful gasesDisadvantages – very few suitable sites. |
ColoursDark colours absorb more heat.Light colours reflect more heat
|
