Energy New Flashcards
system
an object or group of objects
what happens when there is a change to a system
energy is transferred
when do objects have kinetic energy
moving energy have energy in their kinetic store
when do objects have gravitational energy gravitational energy
objects gain energy in their gravitational potential store when they are lifted through a gravitational field
Elastic
Objects have energy in their elastic potential store if they are stretched, squashed or bent
Magnetic
Magnetic materials interacting with each other have energy in their magnetic store
Electrostatic
Objects with charge (like electrons and protons) interacting with one another have energy in their electrostatic store
Chemical
Chemical reactions transfer energy into or away from a substance’s chemical store
Nuclear
Atomic nuclei release energy from their nuclear store during nuclear reactions
Thermal
All objects have energy in their thermal store, the hotter the object, the more energy it has in this store
Mechanical working
When a force acts on an object (e.g. pulling, pushing, stretching, squashing)
Electrical working
A charge moving through a potential difference (e.g. current)
Heating (by particles)
Energy is transferred from a hotter object to a colder one (e.g. conduction)
(Heating by) radiation
Energy transferred by electromagnetic waves (e.g. visible light)
principle of conservation of energy
energy cannot be created or destroyed, it can only be transferred from one store to another
what is the total energy transferred into a system equal to
total energy transferred out of they system
how can energy be transferred to the surroundings
dissipated to the surroundings by heating and radiation
efficiency
the ratio of the useful energy output from a system to its total energy output
equation for efficiency
efficiency = (useful energy output)/(total energy output) x 100%
equation for total energy
total energy output = useful energy output + wasted energy
how to represent useful energy in a sankey diagram
straight arrow pointing to the right
how to represent wasted energy in a sankey diragram
arrows that bend away
how to represent total energy in a sankey diagram
left hand side of the arrow represents total energy transferred into the system
method of energy transfer is solids
conduction
conduction
transfer of heat energy through the vibration of particles causing adjacent particles to gain kinetic energy
what are insulators used for in heating
used to prevent energy transfer by conduction
what makes a material a good conductor
if t transfers energy by heating
why are materials containing small trapped air
better insulator
air is a poor conductor, it cannot move around so it must transfer energy by conduction
how does energy transfer in conduction
when a substance is heated, the atoms start to move around(vibrate) more. As they bump into each other, they transfer energy from atom to atom
why are metals good at conducting heat
delocalised electron can collide with the atoms, helping to transfer vibrations through the material and hence transfer better heat
main method thermal energy is transferred in liquids and gases
convection
convection
transfer of heat through fluids by the upwards movement of warmer, less dense fluids
convection currents
-fluid is heated
-molecules push each other apart, making the fluid expand
-makes the hot fluid less dense that the surroundings
-hot fluid rises, and the cooler fluid moves in to take its place
-eventually the hot fluid cools, contracts and sinks back down again
what do objects emit(related to thermal)
infrared radiation
how does the temperature of an object affect the infrared radiation it emits
the hotter the object. the more infrared radiation it radiates in a given time
qualities of a black object in terms of absorbing and emitting
good absorber and emitter
qualities of a dark object in terms of absorbing and emitting
reasonable absorber and emitter
qualities of a white object in terms of absorbing and emitting
poor absorber and emitter
qualities of a shiny object in terms of absorbing and emitting
very poor absorber(reflects) and emitter
experiment to investigate conduction
- Attach ball bearings to the ends of each metal strip 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
experiment to investigate 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 (potassium permanganate) 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
(temp of water and rate of convection indep and dep variable)
why is convection current faster in hot water
the higher the temperature, the higher the kinetic energy of the water molecules
experiment to investigate 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
how to reduce wasted energy transfers by conduction
use materials with a low thermal conductivity(insulators)
how to prevent wasted energy transfers by convection
fluid that forms the currents must be prevented from moving
factors of the effectiveness of a insulator
-thermal conductivity of the material
-density - particles closer together, easily transfer energy to one another more easily
-thickness of the material
how good of conductors are gases
bad
Work done
Energy transferred
work done units
joules OR newton metres
What happens when a force acts in the direction that the object is moving
Object gains energy(kinetic)
What happens when a force acts in the opposite direction to the movement of an object
The object will lose energy, dissipated
work done equation
w = f x d
gravitational energy definition
the energy an object has due to its height in a gravitational field
GPE equation
GPE = mx g x h
gravitational field strength on Earth
10N/kg
kinetic energy definition
the amount of energy an object has as a result of its mass and speed
kinetic energy equation
1/2 x m x v²
power
work done per unit time
equation for power and energy
P = W/t
W = work done
unit for power
watts or joules per second
renewable energy souce
an energy source that is replenished at a faster rate than the rate at which it is being used
how is electricity generated
a turbine is turned, which turns a generator, which generates electricity
how do fossil fuels generate electricity
they are combusted to heat water, and the steam produced can be used to turn turbines
fossil fuel energy transfers
chemical - thermal - kinetic - kinetic - transferred away electricity
fossil fuels
Fossil fuels are combusted to heat water to produce steam that turns turbines to generate electricity
Nuclear
Nuclear fuels are reacted to heat water to produce steam that turns turbines to generate electricity
Bio fuels
Crops are grown to produce ethanol or methane, which can be used in place of fossil fuels
Wind
Wind is used to turn turbines to generate electricity
Hydroelectric
Water is stored at a height, and when released the moving water is used to turn turbines to generate electricity
Tidal
Water is stored at a height (by a tidal barrage) at high and low tide, when released the moving water is used to turn turbines to generate electricity
Wave
The motion of the water due to waves is used to turn turbines to generate electricity
Geothermal
Hot rocks underground are used to heat water to produce steam that turns turbines to generate electricity
Solar cells
Solar cells use sunlight to generate electricity
Solar panels
Solar panels use sunlight to heat water in the panel to produce warm water for households
fossil fuels advantages
Reliable. Can produce large amounts of energy consistently. Can respond to changes in demand.
fossil fuels disadvantages
Produces carbon dioxide (CO2) which contribute to global warming, and sulphur dioxide, which causes acid rain
nuclear advantages
Reliable. Produces large amounts of energy consistently. Produces no pollution or CO2. Large amounts of energy are produced from small amounts of fuel.
nuclear disadvantages
Produces radioactive waste that takes thousands of years to decay and must be safely disposed of. Nuclear power stations are expensive to build and maintain, and take many years to build. Can not be turned on and off quickly so cannot respond to changes in demand.
Bio fuels advantages
The CO2 released from combustion is balanced by the CO2 absorbed in photosynthesis, so could be considered carbon neutral
bio fuels disadvantages
Land and resources used to grow crops are needed to grow food crops
wind advantages
Produces no pollution or CO2. Are cheap to build and maintain. can be offshore. only small number of turbines required
wind disadvantages
Non-reliable. Only generate electricity when the wind is blowing in a certain direction. Some people consider them visual pollution (they spoil the view)
tidal energy advantages
Tides are very predictable, so energy can be produced at regular intervals
tidal energy disadvantages
Few suitable locations (estuaries). Can harm aquatic life and disrupt shipping
geothermal energy advantages
Reliable
-does not take up a lot of land
geothermal energy disadvantages
Not many suitable locations. Can release methane (a greenhouse gas) in the extraction process.
solar energy advantages
Produces no pollution or greenhouse gases. Good for electricity production in remote areas. Can be put on existing buildings
solar energy disadvantages
Non-reliable. Only generates electricity when the Sun is shining. Each solar cell only produces a small amount of electricity so many cells are needed.
advantages of renewable energy
-no GHGs produced
-does not run out
