Energy Flashcards
Energy stores to know
- thermal
- kinetic
- gravitational potential
- chemical
- magnetic
- electrostatic
- nuclear
- elastic potential energy
Ways in which energy is transferred
- mechanically (by a force doing work)
- electrically (work done by moving charges)
- heating or radiation (light or sound)
What is a system
- a single object or a group of objects
What happens when a system changes
Energy is transferred into or away from the system, between different objects in the system or between different energy stores
What is a closed system
A system where neither matter or energy can enter or leave. The net change in the total energy of a closed system is always zero
Explain energy change of ball going upwards
- initial force exerted by person to throw ball upwards does work
- causes energy to transfer from chemical store of the person arm to the kinetic sore of the ball and arm
Explain energy change from ball being dropped
- dropped from a height: accelerated by gravity
- gravitational force does work
- causes energy to be transferred from the ball’s gpe store to its kinetic store
Energy change when a car brakes
- friction between car’s brakes and its wheels: work is done as it slows down
- causes energy transfer from wheel’s kinetic store to the thermal store of the surroundings
Energy change in car colliding with stationary object
- normal contact force between car’s brakes and and object does work
- causes energy to be transferred from the car’s kinetic store and other stores eg. The elastic potential store and thermal stores of the object and car body
- some energy might be transferred away as sound waves
What is specific heat capacity
- the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree celcius
Experiment to investigate specific heat capacity
- To investigate a solid material you need a block of material with 2 holes in it (for thermometer and heater to go into)
- Measure mass of the block, then wrap it in insulating layer to reduce energy transferred from block to surroundings
- Measure initial temperature of the block and set the potential difference of the power supply to be 10V. Turn on power supply and start a stopwatch.
- When power is turned on, the current in the circuit does work on the heater, transferring energy electrically away from the power supply to the heater’s thermal store by heating, causing the material’s temperature to rise
- As block heats up, take readings of the temperature and current every minute for 10 minutes. Current shouldn’t change as block heats up
- When readings are collected, turn off power supply and calculate power supplied by heater ( P= IV ) and use this to calculate how much energy has been transferred to heater ( E = Pt )
- Plot graph and work out gradient
- Specific heat capacity = 1/ gradient x mass of block
Conservation of energy principle
Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
What is dissipated energy
- sometimes called wasted energy because its not being stored usefully
Explain dissipated of energy in a mobile phone
- system
- energy is usually transferred from the chemical energy store of the battery in the phone
- some of this energy is dissipated into the thermal store of the phone
Dissipation of energy in a closed system: spoon and soup
- a cold soon is dropped into insulated flask of hot soup which is then sealed
- assume flask is perfect thermal insulator so the spoon and soup form closed system
- energy is transferred from thermal energy store of the soup to the useless thermal store of spoon
- energy transfers have occurred within system, but no energy has left the system, so the net change remains 0
What is power
- the rate of energy transfer or rate of doing work
What does lubrication do
- whenever something moves, there’s usually at least one frictional forces citing against it
- this causes some of the energy in the system to be dissipated
- lubricants reduce the friction between objects surfaces when they move
What is thermal conductivity
- a measure of how quickly energy is transferred through a material through heating
- materials with a high thermal conductivity transfer energy between their particles at a faster rate
What is conduction
- energy is transferred to the kinetic stores of its particles
- this causes the particles to vibrate more and to collide with eachother
- during these collisions, energy is transferred between the particles’ kinetic store
What is convection
- if the particles are free to move in a gas or liquid, the particles moving faster means that the space between individual particles increases
- this causes density of the region being heated to decrease
- because liquids and gases can flow, the warmer and less dense region will rise above denser, cooler regions
- energetic particles move away from hotter to cooler regions
What insulation methods can you do to prevent het escaping your home
- have thick walls made from a material of low thermal conductivity: this will slow the rate of energy transfer the building will cool more slowly
- use thermal insulation
Is an device 100% efficient
- NO
- apart from electric heaters: all the energy in the electrostatic energy store is transferred to “useful” thermal energy stores
3 min fossil fuels
Coal
Oil
Natural gas
What are fossil fuels
Natural resources that form underground over millions of years. Typically burnt to provide energy
Why are fossil fuels bad
- they will all run out one day (non-renewable)
- they all do damage to the environment
- but they provide most of our energy
Example of renewable energy resources
- solar
- wind
- bio fuel
- tides
- geothermal
- hydro-electricity
- water waves
Information about renewable resources
- will never run out, the energy can be ‘renewed’ as it is used
- most do damage to the the environment but in less nasty ways than non-renewables
- they don’t provide provide much energy
- some are unreliable because they depend on the weather
Non-renewable resources in transport
- petrol and diesel powered vehicles use fuel created from oil
- coal is used in some old fashioned steam trains to boil water to produce steam
Renewable sources in transport
Vehicles that run on pure bio fuels or a mix of bio fuel and petrol o diesel
Non renewable resources in heating
- natural gas is the most widely used fuel for heating homes in the K
- coal industry fireplaces
- electric heaters
Renewable resources in heating
- geothermal heat pump
- solar water heaters
Pros and cons of wind power
- initial costs are quite high but there are no fuel costs ad minimal running costs
- no permanent damage to landscape
- no pollution
- spoil the view
- noisy
- when wind stops or if wind is too strong its impossible to increase supply
Solar cells pros and cons
- no pollution
- in sunny countries its very reliable b
- initial costs are high but afterwards the energy is free and running costs almost nothing
-only work in daytime
- generate electricity on small scale
Geothermal power pros and cons
- brilliant free energy
- very reliable
- does very little damage to environment
- not many suitable locations for power plants
- cost of building power plant is often high compared to energy it produces
Pros and cons of hydro electric power
- no pollution
- can provide immediate response to increased demand for electricity
-always reliable unless theres a drought - initial costs are high but no fuel costs and minima running costs
-big impact on environment as flooding of valley causes rotting vegetation to release methane ad CO2 and loss of habitat for some species
Pros and cons of wave power
- no pollution
- useful on small islands
- initial costs are high but no fuel costs and minimal running costs
- fairly unreliable, waves die
- disturbs sea bed and marine life habitats
Tidal barges pro and cons
- no pollution
- pretty reliable in the sense that the tides will always happen at the expected time
- initial costs high, no fuel costs and minimal running costs
- has potential for generating a significant amount of energy
- prevent free access to boats
- height of tide is unreliable
Bio fuels pros and cons
- supposedly carbon neutral
- fairly reliable
-cant respond to immediate demands
-very high cost
-large areas of forest have been cleared to make space for bio fuels, loss of habitat
Environmental effects of non renewable resources
- CO2 methane and others released in to atmosphere: contributes to greenhouse effect an global warming
- releases soulful dioxide: acid rain
- coal mining ruins landscape
- oil spillages make serious environmental problems
