Conservation andn dissipation of energy

• A system can be an object or group of objects.
• There is a change in energy stored when a system changes.
• Energy can be transferred through heating, work done by forces, work done when a current flows, electromagnetic radiation, and mechanical radiation.
• 10^3 J is equal to 1KJ.
• Energy cannot be created or destroyed, it can only be transferred between stores.
• Light, sound, and electrical energy all have in common that they can be transferred.
• Energy is transferred from one store to another but not created or destroyed.
• The equation for kinetic energy is 0.5 * mass * speed^2 (velocity).
• The equation for elastic potential energy is 0.5 * spring constant * extension^2.
• The equation for gravitational potential energy is mass * gravitational field strength * height.
• When forces work on a object, the energy store of the object changes.
• The equation for power is energy transferred divided by time or work done divided by time.
• Power is the rate at which energy is transferred or the rate at which work is done.
• Change of thermal energy is the amount of thermal energy stored in or releases from a system.
• The equation for change in thermal energy is mass (kg) * specific heat capacity (J/kg0C) * temp change (0C).
• Specific heat capacity is the amount of energy required to raise the temperature of 1Kg of substance by 1oC.
• Energy can be transferred usefully, stored or dissipated.
• Dissipation is the wasting and spreading out of thermal energy into the surroundings.
• All energy in a home’s thermal store will be dissipated to the outside eventually.
• To slow down the process of thermal energy transfer, insulate loft carpets, insulate floors, windows and doors are draught proofed, and thick walls are used.
• Reduced dissipation increases the efficiency of intended energy transfer.
• Non-renewable resources will run out because there are finite resources which cannot be replenished.
• Efficiency is defined as the useful output energy transfer divided by the total input energy transfer, or the useful power output divided up the total power input.
• Double glazing reduces energy transfer through windows by trapping a layer of air between two panes of glass.
• Home heating is gas & electricity, with some homes having oil-fired boilers and some burning solid fired (coal & wood).
• Green house gases are gases that trap radiation in Earth’s atmosphere, contributing to global warming.
• Fossil fuels generate 50% of the world's electricity.
• Production requires a balance between our needs and environmental issues.
• Thermal conductivity is the measure of how quickly energy is transferred by conduction through it.
• Renewable resources generate 30% of the world's electricity.
• Negatives of wind turbines include being noisy and spoiling the look of the countryside.
• Low thermal conductivity means energy stills flow through it.
• Streamline cars have less of air resistance, which can be reduced by lubricating moving parts with oil.
• Thermal insulation helps keep things warm/cool for longer by reducing unwanted transfers of energy in a system.
• Electricity is used for transport, with oil producing petrol, diesel & kerosene, and electricity is also used to run trains.
• An energy store sets in motion a resource that moves past a turbine, which drives an electrical generator.
• Renewable resources will never run out because these can be replenished.
• Negatives of hydroelectric turbines include affecting the flow of rivers, which can lead to floods and may require communities to relocate.
• Negatives of tidal barrages include affecting the habitat of wildlife.
• An insulator traps a layer of air in its fibres, as air carries energy by convection.