Y8 Energy Stores / Transfer

• different stores of energy are... electrical, gravitational, magnetic, elastic, kinetic, nuclear, thermal, internal and chemical
• when changes occur energy is moved from one store to another
• energy cannot be created or preserved
• the total energy stored in a system remains the same, this is known as the law of conservational energy
• energy transferred from a hotter object to a colder object via conduction is called thermal energy transfer
• sankey diagrams are used to show the proportion of energy transferred into useful and wasted stores
• particles gain thermal energy and vibrate more
• vibrations are passed on to neighbouring particles by conducting/conduction
• many solids are good conductors because the particles are close together
• materials which trap air are good insulators as gases are unable to conduct heat
• metals are the best thermal conductors because they have free electrons to transfer the energy
• thermal equilibrium - if left for long enough in a room, all objects will be at the same temperature
• nuclear store -> radiation -> thermal/chemical store
• all objects that are hotter than their surroundings will emit infra-red waves
• matte, black surfaces are GOOD emitters of thermal radiation
• silver, shiny (or white) surfaces are poor emitters of thermal radiation
• houses in hot countries are painted white to reflect infra-red radiation (thermal radiation) so its cooler
• matte, black surfaces are GOOD absorbers of thermal radiation
• silver, shiny (or white) surfaces are good REFLECTORS of thermal radiation
• vacuum flasks work because: the vacuum section has no air so the thermal energy has nothing to pass through, preventing conduction and convection. also, the silver, shiny surface is a poor emitter but a good reflector so it reduces thermal transfer via radiation. also, the lid stops thermal energy flowing through the top of the bottle
• the rainbow colours are - red, orange, yellow, green, blue, indigo and violet
• the primary colours in light are blue, green and red
• if white light falls on magenta trousers, they will look magenta. if green light falls on them, they will look black.
• the angle of the incidence is always equal to the angle of reflection
• sound is produced by vibrations
• sound waves travel fastest through dense solids because the vibrations are easier to pass on when the particles are closer together
• waves increase speed at the boundary between water and air and blend away from the normal line
• when sound reflects from an object we call it echo
• animals such as bats and dolphins use this to detect where their prey is located
• if a sound doesn't reflect after hitting an object, it will have been absorbed
• light always travels in straight lines
• sound is carried by waves
• sound is caused by vibrations
• the three thermal energy processes are - mechanical, thermal and electrical