Flashcards in module 1 Deck (101):
What are the energy stores?
thermal, kenetic, gravitational potentia, elastic potential,chemical, magnetic, electrostatic, neulear.
What is a system and what happens when they change
a single object, energy is transfered.
How does a system change?
it can be transferred into or away from the system between different objects in a system or between different objects in a system or between different types of energy stores
What are closed systems?
Systems where neither matter nor energy can enter or leave. The net change in teh total energy of a closed system is always zero.
In a boiling kettle what is the system? What energy store is is transfered into?
Water, water heating element and water are two-object system, thermal energy store.
How does energy transfer in kettle?
electrical to thermal energy store of heating element. Then by heating to water's thermal energy store.
What does work done mean?
What can work done be compleated by?
electric flow, by a force moving on object
What is the first stage of someone throwing a ball in the air?
initial force exerted by person throws ball in air. Energy transferes from chemical energy store in arm to kinetic energy store of ball and arm
What is the second stage of a ball in air?
ball dropping accelerates from height by gravity, gravitational force does work. Energy transferes from ball's gravitational potential energy store to its kenetic energy store.
How do energy and forces act on cars?
friction between car's brakes and its wheel does work as it slows down. Energy transferes from wheel's kinetic energy store to thermal store of its surroundings.
What happens in a car crash?
contact force between car and object does work, transfer from car kentic to other energy stores, some energy might be transfered by sound waves.
What are the 3 most common energy stores?
kenetic, gravitation potential, elastic potential
What does everything moving have? What happens with speed?
Kenetic energy store, accelerate- energy transfered to this store. Energy transfered away when it slows.
What does kinetic energy store depend on?
Mass and speed,Greater mass and faster the speed more energy in the kinetic energy store.
What is the formula for kinetic energy?
E(k)=1/2MVsquared m=mass kg v=speed m/s squared. E(k=(j)
What does lifting an objects gravitational field require?
work, causes transfer of energy to gravitational potential energy. Higher lifted more energy is transferred.
What does energy in gravitatial potential depend on?
mass, height, and strength
What is the equation for gravitational potential energy?
E(p)=mgh m=mass kg g= gravitational field strength (N/kg) h= height metres e(p)= (j)
What happens when an object falls?
gravitational potential energy store transfers to kenetic energy store. If no air resistance energy lost from gravitational potential energy =energy gained from kinetic energy store.
What happens with air resistence?
energy is transfered to other energy stores e.g.thermal energy stores of the object and surroundings
What is elastic potential energy caused by?
Squashing or streaching an object so long as limit of proportionality hasn't been exceeded.
What is the equation for elastic potential energy?
E(e)=1/2ke squared E(e)=(j) k=spring constant (N/m) e= extension (m)
Materials need different amounts of heat energy to warm up than others. What do materials that gain lots of heat do?
Transfer lots of energy when they cool down. They 'store a lot of energy'.
What is specific heat capacity
The amount of energy need to raise the temperature of 1kg of a substance by 1 degree celcius.
What do you need to do to measure the specific heat capacity of a metal?
Get a block of a material with 2 holes (for a heater and thermometer to go into).
Why do you measure the mass of the block and wrap it in an insulating layer?
to reduce the energy transferred from the block to the surroundings. Then insert thermometer and heater.
What do you do after measuring the initial temperature of the block?
set the potential difference of the power supply to 10V. Turn on power supply and start stop watch.
What happens after you turn on the power supply?
the current in circuit does work on heater, transferring energy electrically from power supply to heater's thermal energy store. Energy then transferred to material's thermal energy store by heating. Increasing material's temperature.
What do you do as the block is heating up?
take readings of temperature and current every minute for 10 minutes. Should find current doesn't change as block heats up.
What should you do once you have collected your readings?
turn off power supply. using current and potential difference of power supply calculate the power supplied to heater using P=VI
What do you do with the equation P=VI
calculate how much energy has been transferred by the heater at time of each temperature reading using E=Pt E= energy (j)t=time (seconds) since experiment began
What can you do if you assume all energy supplied to heater has been transferred to block?
Plot graph of transferred energy to thermal energy store of block against temperature. Should have curve at beginning and then straight line.
What is the equation for specific heat capacity?
Change in E=MC change in temperature change. e= thermal energy (j) m= mass (kg) c = specific heat capacity (j/kg degrees Celsius).
How do you find the gradient?
change in temperature change divided by change in energy. Using equation for specific capacity equation, use equation 1/(gradient *mass of block) to find specific heat capacity.
Why repeat with other materials?
to compare specific heat capacity.
What is the example as a phone for conservation of energy and power?
useful energy transferred fro chemical store of battery. Some dissipated and transferred. to thermal store
What is the example for a flask for conservation of energy and power?
cold spoon dropped in to sealed flask. Energy transferred from thermal energy store of soup to useless thermal energy store of spoon. Energy transferred within system no energy lost- net charge in energy = 0.
What is power?
Rate of transfer or rate of doing work.
What does 1 watt equal?
1 joule of energy transferred per second.
What are the equations for power?
P=E/T and P=W/T P= power (W) E=energy transferred (j) T=time (S)
What is a powerful machine?
a machine that transfers a lot of energy in a short space of time. Not always what exerts most force.
What is shared across kinetic energy stores of particles in object?
energy transferred to object by heating transferred to thermal store of object.
When heat is added to particles they speed up causing more collisions. What do collisions cause?
When does conduction stop?
when energy is transferred to other side of object
What is thermal conductivity a measure of ?
how quickly energy is transferred through material in this way. Materials with high thermal conductivity transfer energy between particles quickly.
Where is energy shared in convection?
How does density change with heating particles?
Larger space between particles-density of heated region to decrease.
What will happen to less dense regions in convection?
Less dense region will rise above denser regions. If constant heat source convention current will form.
How is heat transferred from radiator to nearby particles?
What force acts on moving objects?
friction causes some of energy in system to be dissipated. Air resistance transfer energy from falling object from kinetic energy store to thermal energy store.
What are lubricants?
Objects rubbed together e. e.g.liquids (oil). Used to reduce friction between objects' surfaces when they move. They can flow between objects easily and coat them.
What will keep a house warmer?
Thick walls with low thermal conductivity material. Thicker walls and lower thermal conductivity slower rate of energy transfer.
What are cavity walls?
made from inner and outer wall, with air gap in middle. Air gap reduces energy lost by conduction through walls. If insulation in air gap filled with foam reduce energy transfer by convection.
What d double glazed windows have?
2 sheets of glass with air in middle to reduce energy transfer by convection.
What do draught exculders do?
reduce energy transfer by convection around doors.
How to test for effective insulation?
Pour water into kettle. Pour some into sealable container at safe level. Measure water mass.
What are the 2nd and 3rd steps and onward to test for insulation?
use thermometer to measure initial temperature of water, seal container and leave it for 5 minutes. Remove lid to measure final temperature. Pour away water and allow container to cool down. Repeat experiment. Keeping fair test.
What does lower temperature difference mean?
Less heat loss e.g. cotton wool.
What do thicker materials mean?
Better thermal insulator.
Why is useful devices useful?
Because they transfer energy from 1 store to another.
How do you improve efficiency of devices?
insulation, lubrication, streamline.
What is equation for efficiency?
efficiency=useful energy transfer/total energy transfer. Or efficiency=useful power output/total power input.
What devices are 100% efficient?
Electric heaters. Transfer all electric energy to thermal energy stores.
What does all energy ultimately get transferred to?
Thermal energy stores.
What are the 3 main fossil fuels
coil, oil, (gas) natural
What are the the renewable sources of energy?
Solar, wind, water waves, hydro-electricity, bio-fuel, tides, geothermal. damage environment less than non-renewable energy, generate less electricity, unreliable, damage environment less.
What are non-renewable sources for fuel in transport?
petrol and diesel from oil. Coal in old trains to boil water to produce steam.
What are renewable sources for fuel in transport?
What are non-renewable sources of energy for heating?
natural gas most widely used for heating in UK. Used to heat water which is pumped into radiators. Coal burnt in fire places, electric heaters (storage heaters) use electricity generated from non-renewable sources.
What are renewable sources of heat?
geothermal use heat pump uses geothermal sources to heat buildings, solar water heater use sun to heat water then pumped to buildings, bio-fuels or renewable energy used for heating.
Where must wind turbines be placed? What is inside it , and does it create pollution?
on moors or round coast. Each turbine has generator to produce electricity, only create pollution when manufactured.
What are disadvantages to wind turbines?
Spoil view. Need 1,500 turbines per 1 coal-fired power station-need lots of ground, noisy, stop when no or too much wind. Generate electricity 70-85% of time. High initial costs small running cost.
What are positives if turbines removed?
no permanent damage to landscape no noise.
How and where do solar panels generate electricity?
Directly from sun, used e.g. calculator minimal electricity needs. Generated in remote places e.g. deserts for road signs and satellites. No pollution (needs lots of energy to manufacture)
What are negatives of solar power?
need to get large amount of sun light less cost effective in UK, can't generate at night, high initial costs-after free no running costs generate on small scale.
Where can you generate geothermal electricity?
In areas around volcanic action. Free reliable little environmental damage. generate electricity or heat buildings directly
What are negatives to geothermal?
not many suitable locations high cost for power plant to energy output.
How does hydro electric power work?
flooding of dam, water allowed through turbines no pollution.
What are negatives to hydro electric power?
loss of habitat in flooding ruin landscape when reservoir dries up needs to be put in valley far from humans for less impact. Doesn't work in drought high initial costs, no fuel costs small running costs generate on small scale in remote areas.
What are positives to hydro electric power?
immediate response to increased demand for electricity.
How does wave power work?
Small wave powered turbines around coast connected to generator.
What are negatives to wave power?
no pollution,disturbs seabed and habitat of marine animal spoil view, hazard for boats fairly unreliable waves can die out high initial costs, no likely to generate on large scale, useful on small islands.
What are positives for wave power?
no fuel costs, small running costs.
How does tidal power work?
dams built across river estuaries with turbines when tide comes it fills estuary allowed through turbine at controlled rate. Tides move by gravitational pull of sun and moon.
What are positives of waves?
quite reliable happen twice a day without fail, near to predicted height. At height slower tide. Don't work when same height on either side of barrage happens 4 times a day. average high initial costs, no fuel costs small running costs generate large amount of electricity.
What are bio-fuel made from?
plant products or animal dung. can be solid liquid or gas. burnt to produce electricity or transport fuel. supposedly carbon-neutral debatable only true if plant growth and plant burning are at equal rates.
What are positives of bio-fuels?
fairly reliable short crop growth time can't respond to immediate energy demands-can be stored.
What are negatives of bio-fuel?
high costs might not enough space or water if just grown for bio-fuels. Some large forests are cleared to make room to grow plants. burning plants produces co2 and methane.
What are positives for non-renewables?
reliable, enough fuel to meet demands can respond quickly to energy demand changes. Are running out some may run out in 100 years. high set-up costs cheap running costs, low fuel extraction costs are cost effective to produce energy.
What are negatives of non-renewable s?
release co2 to the atmosphere, adds to greenhouse affect-global warming. Burning coal and oil releases sulfur dioxide-acid rain, harmful to soil, trees and ecosystems.
What reduces acid rain?
taking sulfur out before burned or cleaning emissions.
What are disadvantages to coal oil and nuclear power?
coil- mining/power plants is dangerous to landscape and workers
oil-spillages cause environmental damage on ecosystems. will always happen.
nuclear-clean but nuclear waste is dangerous and difficult to dispose of. relatively cheap high overall costs due to power plants and decommissioning of plant. Plant can cause catastrophic affect to ecosystem.
How has electrical usage changed in the 21st century?
Used less we are making more efficient appliances and we have become more careful with energy usage. We are mostly using fossil fuels and nuclear power.
What are uses for oil?
electricity, fuel and heat.
How so we hope the future will go ?
increase our renewable recourse to 15% by 2020.
Why do we now want to use more renewable sources of energy?
burning fossil fuels is damaging to environment. makes people want to use renewable sources more. we are increasing aware of non-renewable sources running out-should prepare for it.
Why else do we want to use renewables?
governments introduced targets to limit emissions. Pressure on energy providers to produce new power plants to ensure they don't lose money or business. Electric and hybrid cars are becoming more popular.
Why is it difficult to just use renewable due to money reliability and politics?
Scientists supporting use of renewable s can't force people, companies or governments to change their behavior. Building power plants are expensive. The switch will have to be paid by customers of taxes by governments, some people don't want to or can't afford to pay.
Why are people concerned about renewable s beside cost?
Where to put the power plant must be near but not too near people. People don't want their landscape ruined, people don't think they are as reliable and create less power output. Therefore we will have to create more power plants or research how to improve reliability.