Energy Resources and Transfer - Energy Transfers Flashcards
what are the 8 main energy stores (MENGTECK)
M - Magnetic
E - Elastic Potential
N - Nuclear
G - Gravitational Potential
T - Thermal
E - Electrostatic
C - Chemical
K - Kinetic
what is an example of an object with kinetic energy?
anything moving
what is an example of an object with thermal energy?
anything - the hotter the object the more energy in the thermal store
what is an example of an object with chemical energy?
anything that can release energy by chemical reaction
what is an example of an object with gravitational potential energy?
anything in a gravitational force
what is an example of an object with elastic potential energy?
anything stretched
what is an example of an object with electrostatic energy?
two charges that attract/repel
what is an example of an object with magnetic energy?
two magnets that attract/repel
what is an example of an object with nuclear energy?
atomic nuclei going through nuclear reactions
what are the 4 main energy transfers (HERM)
H - Heating
E - Electrically
R - Radiation
M - Mechanically
what is an example of energy transfer by heating?
energy transfer from a hotter object to a colder object
what is an example of energy transfer electrically?
a charge moving through a potential difference
what is an example of energy transfer by radiation?
energy transferred by light/sound waves
what is an example of energy transfer mechanically?
an object moving due to force acting on it
what is the principle of conservation of energy?
Energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed.
what is the relationship between efficiency, useful energy output and total energy output?
efficiency = (useful energy output/total energy input) x 100
how do sankey diagrams show energy?
the energy flow is shown by arrows whose width is proportional to the amount of energy involved. the wasted and useful energy outputs are shown by different arrows.
how can thermal energy transfer take place?
by conduction, convection and radiation
what is conduction?
conduction is the transfer of thermal energy through a substance by the vibration of the atoms within the substance
are metals good conductors?
metals are good conductors because they have free electrons that can move easily through the metal, making the transfer of energy happen faster
what is convection?
- convection occurs in a liquid/gas
- they expand when heated because the particles move faster and take up more volume – the particles remain the same size but become further apart
- the hot liquid/gas is less dense, so it rises into colder areas
- the denser, colder liquid/gas falls into the warm areas
- this forms a convection current, which transfers heat
what is thermal radiation?
thermal radiation is the transfer of energy by infrared (IR) waves, which travel very quickly in straight lines.
what is the role of convection in radiators?
- convection can be helpful by distributing heat energy to heat the whole room
- hot air rises away from the radiator, creating a current of cool air to be heated
how is emission/absorption of radiation related to surface?
– light, shiny surfaces are good reflectors of IR and so are poor at absorbing it
– dark, matt surfaces are poor reflectors and good at absorbing IR
- this means that placed next to a heat source, a dark object would heat up faster than a light one.
how is emission/absorption of radiation related to temperature?
hotter objects emit more IR per second and the higher the temperature the higher the frequency of EM wave emitted
how would you investigate thermal energy transfer by conduction?
- fix the drawing pin to the end of the metal strip using drops of wax.
- position the other end of the metal strip into a bunsen flame.
- record the time taken for the wax to melt and the drawing pin to drop off.
- the fastest time shows the best conductor of heat
how would you investigate thermal energy transfer by convection?
- heat a beaker with coloured fluid / potassium permanganate crystals on one side
- the purple colour will move in the direction of a convection current
how would you investigate thermal energy transfer by radiation?
- measure the temperature a fixed distance from each side of a Leslie cube using thermometers
- heat the Leslie’s cube with boiling water
- measure and record the temperatures every 30 seconds for five minutes, then plot a graph of temperature against time for each side
how would you reduce unwanted heat energy transfer?
use insulation:
- a good insulating material is a poor conductor that contains trapped air, e.g. foam, feathers, glass fibre
- being a poor conductor (non-metal) prevents heat transfer by conduction
- the trapped air prevents convection currents
