Energy Resources And Energy Transfer - Part 1 (T4) Flashcards
What is the law of conservation of energy?
Energy cannot be made or destroyed; it can only be converted from one form to another
If an electric lightbulb receives 200 J of energy and produces 75 J of light, what else would need to be produced to make the equation balance?
125 J of heat
If you put energy into an efficient device it will convert a greater proportion of it into the desired form of output energy. It will use less energy to do the job and as such, cost less to run.
How do you calculate efficiency?
Efficiency = useful energy output / total energy output
What is a Sankey diagram and what are they good for?
- a Sankey diagram is a special type of flow diagram which is drawn to scale and is used to show proportionate input and output
- they can be used to show transfer of energy (or material, or costs), making it easy to see what is happening as the width (top to bottom) of any part of an arrow represents the amount of energy
Despite the law of conservation of energy meaning energy can never be ‘used up’, why is there still a risk of energy conserves depleting from the earth?
- various uses of energy create wasted energy, and not all of that energy remains on the earth for us to use
- for example, when a car moves some of the energy will be converted to heat. Some of this heat energy will be radiated away from the earth and lost…not destroyed, but unavailable for us to use on the earth
- this is where the energy crisis stems from, in that our reserves of energy in the form of fossil fuels like oil and gas are rapidly being used up
What do scientists mean when they talk about “heat death”?
Some scientists believe that all the energy in the universe is ultimately going to be converted to heat energy and eventually everywhere in the universe will end up at the same very low temperature
Heat energy always travels from a region of ……. temperature to a region of …….. temperature
Heat energy always travels from a region of higher temperature to a region of lower temperature
Via what three very different methods does heat energy travel?
- conduction
- convection
- radiation
Define thermal conduction..
- thermal conduction is the transfer of heat energy through a substance without the substance itself moving
- the thermal energy transfers from molecule to molecule through a material
- for example, one molecule gains some heat energy so it vibrates more vigorously, and that energy is passed onto its slower moving neighbours through the bonds they share
What makes metals good conductors of heat?
The outermost electrons are fairly free to move around from atom to atom, so they can carry energy quickly from hot areas to cooler ones
What do we mean when we say free electrons are ‘delocalised’?
- the free electrons in good conductors are often called ‘delocalised’
- this is because they do not stay attached to any one atom in particular
- these delocalised electrons also allow electricity to be conducted in metals
Why do some materials not conduct heat very well?
Because their outermost electrons remain attached to their parent atom, so energy cannot be passed onto the neighbouring atoms very quickly
Give two common examples of conduction…
- the base of a pan on a cooker, which conducts heat from the heat source below to the food in the pan
- the padding in a warm coat that prevents conduction of your body heat into the cold air around you on a winter’s day
What is thermal radiation?
The transfer of heat energy by electromagnetic (infrared) waves
Describe how infrared radiation works in everyday life..
- everything emits and absorbs infrared radiation continuously
- grills and barbecues are good examples of infrared radiation in use
- objects that are much hotter than their surroundings emit or radiate more infrared radiation per second than cooler ones
