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Where is chemical energy stored
food, fuel, batteries
Where is kinetic energy stored
moving objects
Where is thermal energy stored
hot objects
Where is strain/elastic energy stored
stretched, squashed, twisted materials
Where is atomic/nuclear energy stored
atoms
Where is gravitational energy stored
objects in high places
System
something in which we are studying changes
Law of conservation of energy
energy can’t be created or destroyed
Units for energy
Joules (J)
Sankey diagram
shows the amount of energy transferred and where to
Energy transfer diagram
shows energy stores and transfers
Dissipated
spread out into the surroundings
How do mechanical processes become wasteful
when they cause a rise in temperature - energy dissipates through heating to the surroundings
Energy efficiency definition
how good a machine is at transferring energy into useful forms
given in a number between 0 and 1 or a percentage
Energy efficiency formula
useful energy transferred by device
total energy supplied to device
How can you reduce friction
lubrication - making a surface smooth so things can move easily on it
Insulation
slows the pace at which energy is transferred out of a place
Conduction
vibrations passed between particles in a solid
Convection
part of a fluid is warmer (less dense) and rises up, on the other side it is colder (more dense) and sinks down.
this creates a convection current going round in a circle
Radiation
energy transferred through waves, some types (infrared) can pass through solid objects
Thermal conductivity
how well a material allows heat to move through it
can depend on thickness and temperature difference
a good insulator needs low thermal conductivity
Solar energy
heating and lighting from the sun used with solar panels
Wind energy
using wind turbines, kinetic energy of wind turns a turbine
Hydroelectric energy
flowing water turns a turbine
Wave energy
kinetic energy of sea’s waves turned into electricity
Nuclear energy
energy in uranium nuclei is transferred into heating, creates steam and turns a turbine
Fossil fuels
chemical energy in coal, oil, gas transferred into heating, creates steam and turns a turbine
Biomass energy
chemical energy in things that were once alive burned and turned into heating
Geothermal energy
rocks underground are very hot, heat produces steam which turns a turbine
Tidal energy
water trapped behind a dam at high tide is released, turning a turbine
Note
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