Energy Resources and Transfers Flashcards
what are the 8 energy transfers?
- chemical
- kinetic
- gravitational
- elastic
- thermal
- magnetic
- electrostatic
- nuclear
what are the four ways of how energy can be transferred and examples?
- mechanically e.g. when gravity accelerates an object and gives it kinetic energy
- electrically e.g. when a current passes through a lamp and it emits light and heat
- by heating e.g. when a fire is used to heat up an object
- by radiation e.g. when vibrations cause waves to travel through the air as sound, or an object emits electromagnetic radiation
is energy always conserved?
yes - the total energy before is equal to the total energy after
what is efficiency?
the ratio of the useful energy output to the total energy supplied, often expressed as a percentage
what are sankey diagrams used for?
to represent the transfer of input energy into useful output energy and wasted output energy
what is conduction?
when thermal energy is solids and liquids can be transferred by the vibration of particles
what are thermal insulators?
non-metals which are usually poor conductors
how does conduction take place?
- as a substance is heated up, the molecules vibrate more hitting and causing adjacent molecules to vibrate more too, transferring heat energy from hot parts to cooler parts
- because insulators transfer heat much more slowly, they are used to reduce unwanted energy transfer such as in homes
why are metals good conductors?
- the electrons can leave the atoms and move freely among positively charged ions
- as the metal is heated, the ions and electrons vibrate more
- the free electrons collide with ions throughout the metal and transfer heat energy from hot parts to cooler parts
how can thermal energy in fluids be transferred?
by convection
when does convection occur?
when molecules in a fluid (which are fixed together by forces between molecules like in a solid) move from an area of high to low thermal energy
how can you prevent unwanted energy transfer by convection?
by preventing the circulation of a fluid
what happens during convection?
- when part of a fluid is heated, it expands
- the particles move further apart and they become less dense
- therefore it rises up to less dense areas in the fluid
- denser, colder fluid falls down to take its place
what are two examples of convection?
water boilers and hot air balloons
when infrared radiation transfers thermal energy, does it require a medium?
no
what bodies are the best absorbers and emitters of radiation?
black bodies with a dull texture
what bodies are the best reflectors of radiation?
white bodies with a shiny texture
what can shiny surfaces be used for?
to reduce unwanted energy transfer such as on the surface of a vacuum flask
what increases the amount of infrared radiation emitted?
high temperatures and high surfaces areas
when is work done?
when a force moves something through a distance (whenever energy changes forms)
what is work done equal to?
energy transferred
what is power?
the rate at which energy is transferred or the rate at which work is done
what is renewable energy?
energy which can be replenished as quickly as it is used
what are examples of renewable energy?
- wind
- water (hydroelectricity, waves, tides)
- geothermal
- solar (heating systems and cells)
