Energy Resources and Transfer - Energy Transfers

Question 1

what are the 8 main energy stores (MENGTECK)

Answer 1

M - Magnetic
E - Elastic Potential
N - Nuclear
G - Gravitational Potential
T - Thermal
E - Electrostatic
C - Chemical
K - Kinetic

Question 2

what is an example of an object with kinetic energy?

Answer 2

anything moving

Question 3

what is an example of an object with thermal energy?

Answer 3

anything - the hotter the object the more energy in the thermal store

Question 4

what is an example of an object with chemical energy?

Answer 4

anything that can release energy by chemical reaction

Question 5

what is an example of an object with gravitational potential energy?

Answer 5

anything in a gravitational force

Question 6

what is an example of an object with elastic potential energy?

Answer 6

anything stretched

Question 7

what is an example of an object with electrostatic energy?

Answer 7

two charges that attract/repel

Question 8

what is an example of an object with magnetic energy?

Answer 8

two magnets that attract/repel

Question 9

what is an example of an object with nuclear energy?

Answer 9

atomic nuclei going through nuclear reactions

Question 10

what are the 4 main energy transfers (HERM)

Answer 10

H - Heating
E - Electrically
R - Radiation
M - Mechanically

Question 11

what is an example of energy transfer by heating?

Answer 11

energy transfer from a hotter object to a colder object

Question 12

what is an example of energy transfer electrically?

Answer 12

a charge moving through a potential difference

Question 13

what is an example of energy transfer by radiation?

Answer 13

energy transferred by light/sound waves

Question 14

what is an example of energy transfer mechanically?

Answer 14

an object moving due to force acting on it

Question 15

what is the principle of conservation of energy?

Answer 15

Energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed.

Question 16

what is the relationship between efficiency, useful energy output and total energy output?

Answer 16

efficiency = (useful energy output/total energy input) x 100

Question 17

how do sankey diagrams show energy?

Answer 17

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.

Question 18

how can thermal energy transfer take place?

Answer 18

by conduction, convection and radiation

Question 19

what is conduction?

Answer 19

conduction is the transfer of thermal energy through a substance by the vibration of the atoms within the substance

Question 20

are metals good conductors?

Answer 20

metals are good conductors because they have free electrons that can move easily through the metal, making the transfer of energy happen faster

Question 21

what is convection?

Answer 21

• 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

Question 22

what is thermal radiation?

Answer 22

thermal radiation is the transfer of energy by infrared (IR) waves, which travel very quickly in straight lines.

Question 23

what is the role of convection in radiators?

Answer 23

• 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

Question 24

how is emission/absorption of radiation related to surface?

Answer 24

– 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.

Question 25

how is emission/absorption of radiation related to temperature?

Answer 25

hotter objects emit more IR per second and the higher the temperature the higher the frequency of EM wave emitted

Question 26

how would you investigate thermal energy transfer by conduction?

Answer 26

• 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

Question 27

how would you investigate thermal energy transfer by convection?

Answer 27

• heat a beaker with coloured fluid / potassium permanganate crystals on one side
• the purple colour will move in the direction of a convection current

Question 28

how would you investigate thermal energy transfer by radiation?

Answer 28

• 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

Question 29

how would you reduce unwanted heat energy transfer?

Answer 29

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