TOPIC 1 ENERGY Flashcards
what happens when energy is transferred to an object
the energy is stored in one of the objects energy stores
name different type of energy stores
thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic , electrostatic, nuclear
how is energy transferred
1- mechanically
2-electrically
3- heating or radiation
1- force doing work
2-work done by moving charges
3-light or sound
what is a system
how does it transfer energy
a system is a single object(the air in a piston) or a group of objects (two colliding vehicles),
when a system changes - energy is transferred into or away from the system between different objets in the system or different energy stores
what is a closed system
systems where neither matter nor energy can enter or leave, the net change in the total energy of a closed system is always 0
how is energy transferred by heating (kettle example)
boiling water in a kettle-
water is the system
energy is transferred electrically to thermal energy store of kettles heating element
energy is transferred to water by heating to water’s thermal energy store (causing temperature to rise)
how is work done
another way of saying energy transferred, work is done when current flows
(work is done against resistance in a circuit )
or by a force moving an object
what happens when a person throws a ball upwards
energy transfer from chemical energy store of person’s arm to the kinetic energy store of the ball and arm.
what happens when a ball is dropped from a height
a ball dropped from a height is accelerated by gravity.the gravitational force does work, energy is transferred balls gravitational energy store to its kinetic energy store
what happens when a car slows down
friction between car brakes and wheels does work as it slows down.
energy transfer happens from wheels kinetic energy store to thermal energy store of surroundings
what happens between car and stationary object
normal contact force between car and object does work - energy is transferred from car’s kinetic energy store to other stores e.g. elastic potential , thermal energy store of object and car body. - some energy might be transferred away by sound waves
when is energy transferred to kinetic energy store?
when is energy transferred away from this store?
what does the amount of energy in a kinetic energy store depend on ?
when an object speeds up (anything moving has energy in its kinetic energy store, )-
energy is transferred away from this store when an object slows down
the energy in the ke store- greater the mass: faster is goes, more energy in store
how to calculate kinetic energy store
1/2 x mass x speed^2
how is energy transferred to gravitational potential energy store?
what does the amount of energy is gpe store depend on ?
lifting objects store energy in gpe store - lifting requires work.
the higher the object is lifted, more energy is transferred
amount of energy depends on objects mass height and strength of gravitational field the object is in
how to calculate gpe
mass x gravitational field strength x height
what happens when an object falls
energy transfers from gpe store to kinetic energy store
energy lost from gpe store = energy gained in kinetic energy store when there is no air resistance
in real life =air resistance acts on all falling objects, so some energy goes to other stores like thermal store of object and surroundings
what happens when something is stretched
how can you find the elastic potential energy of a stretched spring
stretching ot squashing an object causes energy to transfer to elastic potential energy store
as long as the limit of proprtionality has not been exceeded, you can find the elastic potential energy store of a stretched spring - 0.5 x spring constant x extension^2
what is specific heat capacity
how do you calculate it
the amount of energy needed to raise the temerature of 1kg of a substance by 1 degree celsius
materials that need to gain lots of energy in their thermal energy stores to heat up also transfer lots of energy when they cool down
change in thermal energy = mass x shc x temp change
SPECIFIC HEAT CAPACITY PRACTICAL
1- solid material (e.g. copper) block of material w 2 holes in it for heater and thermometer- put heater in one hole, thermometer in a hole
2- measure mass of block, wrap it in insulating material (newspaper) to reduce energy transferred t surroundings
3- measure initial temp of block, set p.d. of power supply to 10 V- turn on supply start stopwatch
4-when power is on, current does work , transfers energy electrically from power supply to heaters thermal energy store. then goes to materials thermal store by heating. materials temp rises
as block heats- note temp and current every min for 10 mins (current should not change )
with readings calculate power with p.d x current
calculate energy at each temp with power x time
plot graph of energ transferred (x axis) to block , temp (y axis)
gradient is temp change/ thermal energy change
shc= 1/ gradient x mass of block
what is wasted energy?
when energy transfers between stores, not all is transferred usefully, some energy is dissipated. (usually thermal energy stores)
e.g. for phone. energy is usefully transferred from chemical energy store but some is dissipated to thermal energy store of phone
energy transfers for closed systems?
e.g. cold spoon in soup in sealed flask. spoon and soup make closed system. energy transfers from thermal store of soup to useless thermal store of spoon- soup cools down a bit - energy transfers in system but no energy lost. net change is 0.
what is power how is it calculated
power is the rate of energy transfer/ doing work
measured in watts - 1 watt = 1J of energy transferred
power = energy transferred or work done / time
a powerful machine transfers a lot of energy in a short amount of time
whats conduction
when vibrating particles transfer energy to neighbouring particles
occurs mainly in solids
energy transferred to object by heating goes to thermal store of object. energy is shared inbetween kinetic energy store on particles in object- - particles in heated part of object vibrate and collide more
continues until energy is transferred to other side of object - then goes to thermal store of surroundings
what is thermal conductivity
a measure of how quick energy transfers through a material by conduction.
high thermal conductivity means energy is transferred between particles quicker
whats convection
when energetic particles move away from hotter to cooler regions
-happens in liquids and gases- when u heat gas or liquid, particles move faster. space between particles increase. causes density of region to decrease.
bc liquids and gases flow , yhe warmer less dense region will rise above dense, cool region.
if theres a constant heat source. convection current will be created.
how do radiations make convection currents
1- energy is transferred from radiator to near air particles(that collide w radiation surface) by conduction.
2- air by radiaor becomes becomes warm and less dense. particle move quicker- more space
3- warm air rises , replaced by cooler air - cool air is heated by radiator
4- previously heated air transfers energy to surroundings e.g walls - it cools , goes denser, sinks
this repeats making a convection current
what causes unwanted energy transfers
when something moves theres at least one frictional force acting on it , - this causes energy to be dissipated, or air resistanct can transfer energy from object’s kinetic store to thermal store.
how to reduce unwanted energy transfer
usually liquids like oil- flows easily between objects and coats them -
for objects that are rubbed together. they reduce friction between objects surfaces when moving,
how to reduce energy transfer in homes
thick walls with material of low thermal conductivity. - slower rate on energy transfer, builing cools more slowly
cavity walls- made from inner & outer wall with gap- air gap reduces energy transferred by conduction through wall- gap made from foam- reduces energy transfer by convection in wall cavity
loft insulation can reduce convection currents being created in lofts
double glazed window - air gap betwee two sheets of glass to prevent energy transfer by conduction through window
draught excluders around doors and windows reduce energy transfers by convection
practical - how to investigate effectiveness of materials of thermal insulators
1- boil water in kettle , pour water in sealed container, - measure mass of water in container
measure initial temp w thermometer
seal container leave for 5 mins (w stopwatch) remove lid, measure final temp.
pour away water, allow container to cool to room temp
repeat but wrap container in different material( e.g. foil, newspaper) once sealed - use same mass of water at same initial temp each time
(lowe the temp difference, better the material as thermal insulator )
e.g. bubble wrap, wool is good
or thickness- the thicker- better insulator , the smaller the temp change , less energy transferred -
efficiency
how do you work out efficiency
the less energy that is wasted , the more efficient the device is said to be. - improve efficiency by insulating objects, lubricating them, making them more streamlined,
no device is 100 percent efficient, wasted energy usually goes to thermal
useful output energy transfer/ total input energy transfer
or
useful power output/ total power input
give an example of something that is 100 percent efficient
electric heaters- all energy goes to electrostatic energy store is transferred to useful thermal energy store
what is non renewable energy resources, give examples
resources that will run out one day, damage environment, provide most of our energy
. fossil fuels and nuclear fuel (uranium and plutonium)
fossil fuels are natural resources that form underground over millions of years- burnt to provide energy
main fossil fuels
coal
oil
natural gas
what are renewable energy resources
give examples
will never run out, energy can be renewed as it is used - damage environment less that non renewable
dont provide much energy
some are weather dependent
(sun, wind, water waves, hydro electrcity, bio fuel, tides, geothermal )
how are energy resources used for transport
non renewable- petrol and diesel powered vehicles use fuel from oil
or coal in steam trains to boil water for steam
renwable- vehicles run on pure bio fuels or mix of biofuel-renewable, petrol,diesel
how is energy resources used for heating
non renweable
natural gas is used as fuel for heating homes, gas used to heat water - pumped into radiators
/coal burnt at fireplace
/electric heaters use electricity generated from nr energy source
renewable
geothermal heat pump
to heat buildings,/ solar water heaters- sunt to heat water thats pumped into radiators of building,/
burning biofuel or using electiricty generated from renewable source to use for heating
what is wind power?
strengths and weakness of wind power
turbine has generator that rotates blades to produce electricity
strengths
no pollution (only a bit when manufactured)/ no fuel costs & minimal running costs/ no permanent damage to landscape- when removed noise is removed
weakness
spoil the view- big effect of scenery/ noisy/ weather dependent- imposible to increase supply if wind stops
solar cells - strengths and weakness
generate electric currents directly from sunlight
strenghths-
no pollution/ reliable source of energy in sunny countries/ after initial costs it is free and running costs almost nil
weakness
requires a lot of energy to manufacture/ only useful in daytime/ cant increase power output when in extra demand / generates electricity on small scale/ initial costs r high
hydro electric power strengths and weakness
requires flooding of a valley by building a big dam- water is allowed out through turbines
strengths- no pollution, it can provide an immediate response to icreased demand for electricity, no problem with reliability except in time of drought , no fuel costs and minimal running costs
weakness- flooding of valley can cause rotting of vegetation releasing methane and co2/ loss of habitat for some species/ reservoirs can look very unsightly when they dry up / initial costs are very high
wave power strengths and weakness
located around the coast- wave powered turbines are connected to generator
strengths
no fuel costs, minimal running cost, no pollution, very useful on small islands
weakness- disturbs seabed and habitats of marine animals/ spoils view/ hazard to boats, unreliable as wave dies ou when wind drops/ initial costs are high / doesnt provide energy on a large scale
tidal barrages
big dams built across river estuaries with turbines in them- tide comes in and fills estuary-water is allowed out through turbines at controlled speed
strength-
happens twice a day without fail so it is reliable always near predicted height/ no pollution/ no fuel costs and minimal running cost
weakness-
prevents free access to boats/ spoils view/ alters habitat/ height of tide is variable so low tides provide less energy that big ones/ dont work when water level is same either side of barrage(happens 4x due to tides)
biofuels
and its strengths and weaknesses
renewable energy resources from plant products or animal dung - burnt to produce electricity or run cars
(debate on whether it is carbon neutral or not bc youre burning things at the rate u are growing things)
strengths- fairly reliable, crops take a relatively short time to grow, biofuels are continuosly produced and stored for when they are needed
weakness- cannot respond to immediate energy demands , cost to refie biofuels are very high, worry that growing crops for bio fuels means there wont be enough sace or water to meet demands for crops that are grown for food, large area of forests is cleared for bio fuels so lots of loss of natural habitat, decay of vegetation increases co2 and methane emissions
non renewables e.g. fossil fuels and nuclear energy weakness and strengths
strengths- reliable- enough to meet current demand, extracted from earth at a afast enough rate , power plants repond quickly to changes in demand/ runnning costs are not expensibe
weakness- fuels are slowly running out if no new resources are found then stocks may run out in hundred of years , set up costs can be quite high
-coal oil gas releases co2 into environment adding to greenhouse affet adding to global warming
- burning coal and oil releases sulfur dioxide which makes acid rain - harmful to ecosystems
- coal mining causes mess to landscape
-nuclear waste is dangerous and difficult to expose of
- oil spillages affect environment and habitats
- overall cost of nuclear power is high c of cost of power plant and final decomissioning
- nuclear power can causes disasters
explain use of fossilfuels in the uk
over 20th century- use of electricity increased as population grew, people used energy for more things,
begining of 21st century- electricity use drecreasing as appliances are most efficient and more careful with energy in our homes
most electricity from fossil fuels from nuclear power
fossil fuels- oil to fuel cars, gas to heat homes and cook foods
we are trying to increase use of reneweable sources
why do people want to start using mor erenewable energy resources
fossil fuels are very damaging to the environment, non renewables will run out one day,
pressure from other countries and publi to intriduce targets for using renewable resources
pressure on energy providers to build new power plants to use renweable so they dont lose business or money
car companies affected- electric cars and hybrids on market and popularity is increasing
how is the use of renwables limited
money- building non renewable power plants costs money- energy providers are reluctant bc fossil fuels are so cost effective, cost of switching will have to be paid
people dont want to live near wind farms etc
energy resources like wind power are not reliable as they cant increase
power output on demand
improviing reliability and cost of renwables takes time and money-
personal changes can be quite expensive, hybrid cars r expensve, solar panels r pricey,
geothermal energy
strengths and weakness
occurs in volcanic areas where hot rocks lie near to the surface. it is the slow decay of radioactive elements e.g uranium deep inside earth
good- free energy that is reliable, little damage to environment, for generating electricity and heating buildings
bad- not many suitable locations for power plants , cost of building a power plant is high compared to amount of energy it produces
