P1 - All Topics Flashcards
Why is it best to paint the outside of a metal cooking pot black?
Because black is a good absorber of heat. The heat will be used to cook the food.
Why does a cooking pot have a lid?
To reduce energy loss by convection.
Why is a car radiator painted black?
Black is a good emitter of heat, the heat is emitted to the surroundings to keep the engine cool.
Explain why thermal imaging cameras work better at night than during the day.
At night the surroundings are cooler so the surroundings emit less IR radiation than the warm body and this gives a clearer image.
What is the name given to heat transfer from particle to particle?
Conduction
What name is given to the heat transfer by the movement of hot liquids?
Convection
Why is the outside of a fire fighter’s suit shiny?
To reflect heat away from the fire fighter.
How is heat transferred through a metal?
Free electrons inside the metal gain kinetic energy and collide with the metal ions.
Why are radiators painted white and not black?
if they were painted black, they would transfer heat too quickly and the watertemperature inside theradiator would drop too quickly. The next radiator would then stay cold.
How does the Sun transfer heat?
Radiation
A bag is filled with water and placed in the Sun. What colour should the bag be so that the water can be warmed?
Black, as black surfaces are good absorbers and emitters of thermal energy. Heat from theSun is absorbed and used to heat the water.
Which methods of heat transfer are reduced by a vacuum?
Convection and conduction as both require particles.
which method of heat transfer is reduced by silver surfaces?
Radiation; heat is reflected
Which methods of heat transfer are reduced by plastic caps?
conduction as plastics are good insulators & convection
Why does a fridge have a white shiny surface?
A white shiny Surface is a poor absorber of heat and reduces heat transfer into the fridge. The heat is reflected instead.
how is energy transferred from the base of a sauce pan to the water inside the pan?
water particles at the bottom gain energy and move faster; the density of water decreases; hot water rises and is replaced by cold water
What is thermal radiation?
infra red radiation
Why does warm water freeze quicker inside a freezer than cold water?
The rate of heat transfer is greater with warm water.
why does 1kg of a gas have a larger volume than 1 kg of a solid?
There are strong forces of attraction between the particles in a solid holding the particles close together. In a gas the forces are very small so the particles can spread out.
Why does the temperature of a liquid decrease as the liquid evaporates?
the particles with most energy leave the liquid and the mean energy of the remaining particles decreases so the temperature goes down.
Why does sweating cool you down?
To evaporate the sweat requires energy which is taken from the skin/body.
How can you speed up evaporation?
Increase the surface area; use wind/draughts to allow particles with high energy to escape from the liquid
Describe the arrangement of particles in solids, liquids and gases.
In solids, particles vibrate around fixed positions. In liquids they are arranged in a pattern, in gases they move at high speed in any direction.
What is the ideal weather for drying clothes outside?
Warm/sunny and windy
<p>Define renewable energy</p>
<p>An energy source that is replaced faster than it can be used.</p>
Give examples of renewable energy sources.
Wind, waves, tides, hydroelectric, biofuel, geothermal, solar
How does the step-up transformer increase the efficiency of the National Grid?
It increases the voltage and decreases the current, therefore reducing energy loss along the cables.
Explain one effect burning fossil fuels has on the environment.
produces greenhouse gases, nitrogen oxides (trigger asthma attacks), sulphur dioxide (leads to acid rain)
Pumped storage hydroelectric power stations have a short start-up time. Why is this important?
to meet surges in demand/ start generating electricity in a short time
<p>Give an advantage of a pumped storage hydroelectric power station.</p>
<p>can store energy for later use/ renewable</p>
Using mainly wind turbines to supply electricity might cause fluctuations in the electricity supply. Why?
wind speeds fluctuate so turbines don’t generate electricity at a constant rate
Between 2002 and 2008 the amount of electricity used in the UK decreased. Suggest why.
energy efficient lighting used/ developed; increase in energy costs so people switch off more; ‘switch off’ campaign raises awareness of environment
Although gas boilers are very efficient, some energy is wasted. What happens to this waste energy?
it is transferred to the surroundings, becomes spread out; wasted as sound
Give a disadvantage of a large scale hydroelectric power station.
large areas of land flooded, homes and habitats destroyed
What is the National Grid?
system of cables and transformers
Why is transferring electricity directly to local homes more efficient than using the National Grid?
less energy is wasted as the cables used are shorter
A solar cell can be used to recharge a mobile phone. Suggest and explain one factor that would affect the charging time.
time of day, position of solar cell, angle of solar cell towards Sun, latitude, cloud cover, dust; all cause a change in light intensity
What are the advantages of using solar cells instead of fossil fuel power stations to generate electricity?
no air pollution, free resource, renewable, usable in remote areas, no need to connect to National Grid
Fitting a new hot water boiler costs £1800 but saves £200 per year. What is the payback time?
9 years
Explain why using an energy efficient light bulb rather than an ordinary light bulb reduces carbon dioxide emissions.
less electricity needs to be generated from power stations, less fossil fuel needs to be burnt
Give two advantages of burning wood instead of coal.
carbon neutral, renewable, conserves fossil fuel reserves
Why do wood burning stoves have a large surface area?
to increase the rate of energy transfer
Do you agree with the statement that ‘replacing old freezers with more energy efficient freezers’ benefits the environment?
y- less fossil fuels burnt as less electricity needed, so fewer greenhouse gases emittedn- old freezers must be dumped and there are hazardous chemicals inside them
How do you reduce energy loss from the loft/roof?
Fibreglass
How do you reduce energy loss from the walls?
Cavity wall insulation such as polystyrene beads
How do you reduce energy loss from windows?
double/ triple glazing
How do you reduce energy loss from doors?
draught excluders
why are electricity companies selling electricity at night at a lower rate?
Supply exceeds demand
Leaving a 1kW radiator switched on for the same length of time as a 40W lamp is worse for the environment. Why?
radiator uses more energy,more electricity is needed,more fossil fuel is burnt, moreCO2 produced
<p>What is meant by the word efficient?</p>
<p>most input energy isusefully transformed</p>
Give examples ofstored energy.
gravitational, elastic,chemical
Why must the totalenergy input equal the totalenergy output?
energy cannot be createdor destroyed
Name the useful andwasted energy output from ahair dryer.
useful thermal and kineticand wasted sound energy
Name the useful andwasted energy output from aTV.
useful sound and light,wasted thermal
what does it mean todecommission a nuclearpower station?
remove radioactive waste/fuel- very expensive process
How could companiesreduce CO2 emissions?
use more nuclear power,use more renewable energysources, use carbon capturetechnology
Give the advantages ofusing nuclear power.
little fuel needed for a largeamount of energy released(concentrated source of energy),continuous process, nogreenhouse gas emissions
give advantages anddisadvantages of tidal powergenerating systems.
renewable, calms coastalwaters, low running costs, noair pollution but highinstallation costs, timedependent, disturbs coastalhabitats
Give advantages anddisadvantages of wind power.
renewable, no air pollution,leave land undamaged whenremoved but unsightly andnoisy, require large areas ofland as many turbines areneeded
List the EM wavesfrom longest to shortestwave length.
radio, micro, IR, visible, UV,X-Ray, gamma
State one differencebetween UV and visible light.
UV has a higher frequency,shorter wavelength, has moreenergy
What does redshift tellscientists about galaxies?
that they are moving awayfrom Earth
Why is the redshift notthe same for all galaxies?
galaxies are moving awayfrom Earth at differentspeeds
What does redshiftsuggest about the Universe?
that it is expanding
What happens when ametal aerial absorbs radiowaves?
it creates an alternatingcurrent with the samefrequency as the radio wave
Why would an X-raytelescope placed on Earth notbe able to detect X-raysemitted from distance stars?
X-rays cannot penetrate theatmosphere
Give an example of IRbeing used forcommunication.
TV, remote controls, opticalfibres, remote control,thermal imaging
Give the differencebetween transverse andlongitudinal waves.
oscillations areperpendicular to the directionof energy transferred fortransverse waves but parallelfor longitudinal waves
Why can you hear butnot see the TV in anotherroom?
light waves will notdiffract but sound waves willbecause the width of thedoor is similar to thewavelength of the soundwave.
Why do thermalimaging cameras work betterat night than during the day?
at night the surroundingsare cooler so they emit lessIR than a person; thedifference in IR emitted islarger
Give two properties ofall EM waves.
Travel at the same speed,transfer energy, travel througha vacuum, can be reflected,refracted, diffracted, absorbed,are transverse, travel in straightlines
What is the propertyof microwaves that allowsthem to be used for satellitecommunications?
They can pass through theionosphere.
An image in the mirroris virtual. Why?
Image is formed byimaginary rays crossing;formed behind the mirror
if microwaves areabsorbed by a tennis ball,what effect do themicrowaves have on the ball?
Make it hotter
How does red shiftprovide evidence for the BigBang theory?
Redshift of distant galaxies isgreater which means that thefurther apart galaxies are thefaster they are moving awayfrom each other; relationship isproportional, so must havestarted at same point.
Compare a quiet andlow pitch sound to a loud andhigh pitch sound.
Low pitch has longerwavelength and lowerfrequency/ Quieter sound haslower amplitude
What is cosmicbackground radiation?
Microwave noise thatreaches Earth from manystars and galaxies; radiationcreated just after the BigBang
How do you calculatewave speed?
wave speed (m/s) =frequency (Hz) x wavelength(m)
Describe the Big Bangtheory.
Universe started in oneplace; huge explosion tookplace and sent matteroutwards; Universe has beenexpanding ever since.
What is the Universe?
innumerable collectionof galaxies
What is redshift?
light moves towards thered end of the spectrum
Describe how thesound changes when a cardrives past you.
car drives towards you:wavelength shortens andfrequency increasesCar drives away from you:wavelength lengthens andfrequency decreases
Why do scientists useX-ray, gamma ray andmicrowave telescopes toobserve the Universe?
stars emit different typesof EM radiation
How is the wavelengthof CMBR likely to changeover the next billion years?
increase as Universecontinues to expand
What is the Dopplereffect?
change in wavelength andfrequency when the source ofwaves or observer moves( relative to each other)
Give one example ofmicrowaves being used forcommunications.
Mobile phone/satellitecommunications
What are the dangersof IR, UV and micro waveradiation?
IR- skin burnsUV- skin burns, skin cancerMicrowaves- burns, cancer
Give a use of radiowaves.
TV broadcasting, mobilephone communications
Describe an imageformed in the mirror.
virtual and upright, samedistance behind the mirror asobject is in front of themirror
What is refraction?
when light travels fromone medium to another, itchanges direction because it’sspeed has changed; this isdue to the density of themedium having changed
What are sound wavescaused by?
vibrations
How can you reducethe amount of noisetransmitted through walls?Why does the method work?
panel the walls with woodor plaster or similar so thesound is reflected back orabsorbed
What is diffraction?
the spreading of waves whenthey pass through a gap oraround the edges of an obstaclewhich has a similar size as thewavelength of the wave
How do microwavesheat food?
microwaves are absorbedby the water inside the food,the water heats the food
What does the termfrequency mean?
number of waves persecond
What do the wordscompression and rarefactionmean?
compression is squeezingtogether, rarefaction isstretching apart
Why does the mirrorget misty when you have ahot shower?
water evaporates and goesinto the air, mirror is colderthan the air, water particleshit mirror and lose energy,condensation is caused
How does a vacuumflask keep the liquid insidehot?
plastic cap is poor conductor & stopsevaporation of hot liquid as particlescannot escape; stops convectioncurrents so no heat loss by convection;vacuum prevents heat loss byconduction & convection as both requireparticles; silver lining to reflect IR backinside the flask and reduce heat loss byradiation
Why do arctic foxes havesmall ears?
ears have a small surfacearea so reduce heat loss
What is the law ofreflection?
angle of incidence = angleof reflection
Why is foam a goodinsulator?
air cannot circulate insidefoam as the air bubbles aretrapped inside the foam
What is meant by theterm U-value?
how effective an insulator amaterial is; the lower the Uvalue,the better the material isat insulating
What is geothermalenergy?
energy from hot rocks inthe Earth
Why does theNational Grid include step-uptransformers?
to increase the voltageacross the cables and reduceenergy loss
Why are copper pipesinside a solar panel paintedblack?
black is a goodabsorber of radiation sothere will be a fastertransfer of energy to thewater
Why is electricityessential for moderncommunication and publichealth?
Many devices transform onetype of energy into others;doctors and hospitals can storevaccines and blood inrefrigerators; internet runs onelectricity
What is the role ofthe step-down transformer?
It reduces the voltage to asafe working value for homesand offices
What are the twomain pieces of evidence forthe Big Bang theory?
Redshift and cosmicmicrowave backgroundradiation
