4 Energy resources and Energy transfers Flashcards
what are the 8 energy stores
chemical
kinetic
gravitational
elastic
themal
magnetic
electrostatic
nuclear
what are the 5 energy transfers
mechanically
electrically
radiated sound
ratdiated light
by heating
what is the principle of conservation of energy
energy cannot be created or destroyed only transferred from one form to another
what is the formula with work, distance moved, force
work = force x distance moved
W = F x d
is work done and energy transferred equal
yes
what is the formula with gravitiational potential energy, mass, height, gravtiational field strength
gravitiational potential energy = mass x gravitiational field strength x height
GPE = mgh
what is the formula for kinetic energy
kinetic energy = 1/2 x mass x speed^2
KE = 1/2mv^2
how does conservation of energy produce a link between GPE, KE and work done
if an object falls GPE -> KE and the change in GPE = work done
if an object is thrown up, KE -> GPE and the change in KE = work done
this means that (assuming there is no air resistance) GPE + KE = constant
They are different forms of energy that can be transformed into each other while keeping the total energy constant
what is power
the rate of transfer of energy or the rate of doing work
what is the formula with work done, time taken, power
power = work done / time taken
P = W / t
formula for efficiency
efficiency = useful energy output / total energy output x 100
how does thermal energy transfer take place
conduction or convection or radiation
how does conduction work
When a substance is heated, the atoms start to move around (vibrate) more
As they do so they bump into each other, transferring energy from atom to atom
Metals are especially good at conducting heat as the delocalised electrons can collide with the atoms, helping to transfer the vibrations through the material and hence transfer heat better
how does radiation energy transfer work
When an object has thermal energy, it emits radiation in the form of electromagnetic waves. The amount and type of radiation depend on the object’s temperature and surface properties.
how does convection work
When a fluid (a liquid or a gas) is heated:
The molecules push each other apart, making the fluid expand
This makes the hot fluid less dense than the surroundings
The hot fluid rises, and the cooler (surrounding) fluid moves in to take its place
Eventually, the hot fluid cools, contracts and sinks back down again
The resulting motion is called a convection current
Convection is the main way that thermal energy is transferred through liquids and gases
Convection cannot occur in solids
explain how emission and absorption of radiation are related to surface and temperature
black - good absorber and emitter
dull - ok absorber and emitter
white - poor absorber and emitter
shiny - awful absorber and emitter
practical: investigate thermal energy transfer by conduction
Attach ball bearings to the ends of each metal strip (different metal) at an equal distance from the centre, using a small amount of wax
The strips should then be turned upside down and the centre heated gently using a bunsen burner so that each of the strips is heated at the central point where they meet
When the heat is conducted along to the ball bearing, the wax will melt and the ball bearing will drop
Time how long this takes for each of the strips and record in a table
Repeat the experiment and calculate an average of each time
Order the metals according to their thermal conductivity
The first ball bearing to fall will be from the rod that is the best thermal conductor
This is because materials with high thermal conductivity heat up faster than materials with low thermal conductivity
ways of reducing unwanted energy transfer
to stop conduction: surround with an insulator such as wool as its molecular structure does not allow the particles to vibrate and so stops them bumping into each other and transferring energy
to stop radiation: surround in white shiny wrap as this will reflect the infrared waves back into the source stopping energy being lost
to stop convection: use something with air pockets as the confined pockets prevent a large convection current starting up
practical: investigate thermal energy transfer by convection
Fill the beaker with cold water (not too full) and place it on top of a tripod and heatproof mat
Pick up the crystal using forceps and drop it into the centre of the beaker – do this carefully to ensure the crystal does not dissolve prematurely
Heat the beaker using the Bunsen burner and record observations
Repeat experiment with hot water and record observations
Energy is initially transferred from the Bunsen flame through the glass wall of the beaker by conduction
The water in the region of the Bunsen flame is heated and the space between the water molecules expands, therefore, the water becomes less dense and rises
This causes the dissolved purple crystal to flow upwards with the water
Meanwhile, when the water at the top of the beaker cools, there is less space between the water molecules and the water becomes denser again and falls downwards
The process continues which leads to a convection current where energy is transferred through the liquid
The dissolved purple crystal follows this current which can be clearly observed during this experiment
practical: investigate thermal energy transfer by radiation
Set up the four identical flasks painted in different colours: black, grey, white and silver
Fill the flasks with hot water, ensuring the measurements start from the same initial temperature
Note the starting temperature, then measure the temperatures at regular intervals, e.g. every 30 seconds for 10 minutes
All objects emit infrared radiation, but the hotter an object is, the more infrared waves are emitted
The intensity (and wavelength) of the emitted radiation depends on:
The temperature of the body (hotter objects emit more thermal radiation)
The surface area of the body (a larger surface area allows more radiation to be emitted)
The colour of the surface
Most of the energy lost from the beakers will be by heating due to conduction and convection
This will be equal for each beaker, as colour does not affect energy transferred by conduction and convection
Any difference in energy transferred away from each beaker must, therefore, be due to infrared radiation
To compare the rate of energy transfer away from each flask, plot a graph of temperature on the y-axis against time on the x-axis and draw curves of best fit
energy transfers involved in generating electricity using wind:
Energy is transferred from the kinetic store of the moving wind to the kinetic store of the turbine as the wind makes it turn. Energy is transferred from the kinetic store of the turbine to the kinetic store of the generator and is transferred electrically to the National Grid.
energy transfers involved in generating electricity using water:
electricity is generated in very similar ways, no matter what energy resource is used
A turbine is turned, which turns a generator, which generates electricity
The element that differs is how the turbine is made to turn
Water can be used to turn turbines in the case of hydroelectric dams, tidal barrages and tidal turbines
Energy in the kinetic store of the flowing water is transferred to the kinetic store of the turbine, then to the kinetic store of the generator and transferred electrically to the National Grid
energy transfers involved in generating electricity using geothermal:
Water is pumped down to the hot rocks and returns through a fissure as steam which turns the turbine and powers the generator.
energy transfers involved in generating electricity using solar heating:
Solar panels use sunlight to heat water in the panel to produce steam which turns a turbine which then turns a generator
energy transfers involved in generating electricity using solar cells:
Solar cells, also known as photovoltaic (PV) cells, absorb sunlight. The light energy from the sun is captured by the semiconductor material (usually silicon) in the cells.
Conversion to Electrical Energy: When sunlight hits the semiconductor, it excites electrons, creating an electric charge. This process directly converts light energy into electrical energy.
energy transfers involved in generating electricity using fossil fuels:
Fossil fuels can be combusted to heat water, and the steam produced can be used to turn turbines
Energy from the chemical store of the fuel is transferred to the thermal store of the water, which is then transferred to the kinetic store of the turbine, and then transferred to the kinetic store of the generator and then transferred electrically to the National Grid
energy transfers involved in generating electricity using nuclear:
Nuclear fuels are reacted to heat water to produce steam that turns turbines
Nuclear store of fuel → kinetic store of fission products -> thermal store of coolant -> thermal store of water → kinetic store of steam -> kinetic store of turbine → electrical of generator
advantages and disadvantages of generating electricity by wind
Advantages – renewable, pretty cheap, no atmospheric pollution
Disadvantages – non reliable, not very pretty, uses a large area, location dependent
advantages and disadvantages of generating electricity by nuclear
Advantages – very efficient, a little bit of uranium creates a lot of energy, not location dependent, reliable, high energy density, carbon neutral
Disadvantages – creates nuclear waste which is dangerous and can’t be disposed of easily, can be very bad if it explodes
advantages and disadvantages of generating electricity by fossil fuels
advantages - reliable and non location dependant
disadvantages - non renewable and creates atmospheric pollution which contributes to global warming
advantages and disadvantages of generating electricity by geothermal
Advantages – renewable, reliable, doesn’t contribute to atmospheric pollution.
Disadvantages – location dependent
advantages and disadvantages of generating electricity by hydroelectricity
Advantages – very reliable, renewable
Disadvantages – very expensive and time consuming to build, disrupts ecosystem, location dependent
advantages and disadvantages of generating electricity by tidal/wave
Advantages – reliable, renewable
Disadvantages – very expensive and time consuming to build, disrupts ecosystem, location dependent
advantages and disadvantages of generating electricity by solar heating
Advantages – its renewable, it works all day and it reduces our carbon footprint
Disadvantages – Expensive equipment cost, requires a large area to work, time dependent
advantages and disadvantages of generating electricity by solar cells
Advantages – low maintenance, easy to install, reduces carbon footprint, no atmospheric pollution
Disadvantages - Expensive equipment cost, Weather/daytime dependency, not very pretty, takes up large area
why does hot air rise
air expands (the distance between the molecules increases) when it is hot causing it to decrease in density so rises
