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How does the temperature of an object affect the rate at which it emits Infrared Radiation?
All objects emit IR. The hotter an object, the more IR it emits. It is how we get energy from the sun.
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How does the surface of an object affect how much infrared radiation it emits & absorbs?
Dark matt surfaces = good absorbers + emitters of IR. Light shiny surfaces = Good reflectors + Bad emitters of IR
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How do solids conduct electricity?
If one end of a solid is heated the particles at that end gain kinetic energy & vibrate more and the energy is passed to neighbouring particles.
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Why are metals good conductors?
When heated their free electrons gain kinetic energy & move through the metal transferring energy by colliding with other particles.
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What are poor conductors?
Insulators (i.e. wool/fibre glass as they contain trapped air)
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How do convection currents occur in fluids (liquids/gases)?
When heated fluids expand, become less dense, rise and are replaced by cooler, denser fluid i.e. heating water in a beaker, heating the air above land/sea.
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What is the difference between evaporation and boiling?
Evaporation only affects the surface of the liquid as the most energetic liquid molecules escape the liquid’s surface and become a gas.
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Why does evaporation cause a cooling effect?
The average kinetic energy of the remaining molecules is less, so the temperature of the liquid decreases.
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What can increase the rate of evaporation?
Increasing the S.A, temp of liquid or creating a draught of air across the liquid’s surface.
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What is condensation and how is the rate of condensation increased?
When a gas turns into a liquid. Rate of condensation increased by: increasing the S.A. & reducing the surface temp.
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How is the rate of energy transfer affected?
The greater the temp difference between an object & its surroundings the greater the rate of energy transfer. Also affected by: material object is in contact with + object’s shape & S.A.
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How can we maximise the rate of energy transfer to keep things cool?
Use things that are good conductors, painted dull black & have the air flow around them maximised.
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How can we minimise the rate of energy transfer (conduction/convection/radiation) to keep things warm?
Use things that are good insulators, white & shiny + prevent convection currents by trapping air in small pockets.
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What is specific heat capacity?
Amount of energy required to raise temp 1kg of the substance by 1o. The greater the mass the more energy required for temp change.
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How do people minimise the rate of energy transfer (to reduce fuel bills)? Cond=reduce energy transfer by conduction. Conv=reduce energy transfer by convection.
By fitting: fibreglass loft insulation (cond), Cavity wall that traps air in small pockets (conv), double glazing (cond), draught proofing (conv), aluminium foil behind radiators (to reflect IR back into room).
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What does the U-value of an object tell us?
How much energy per second passes through an object. The lower the U-value the better the material is as an insulator.
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Why are the advantages and disadvantages of Solar heating Panels?
Cheap to run (don’t use fuel) & used to heat buildings/provide domestic hot water but are expensive to buy/install & water isn’t heated at night.
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What are the different forms of energy, how are they measured & which are forms of stored energy?
Light, sound, kinetic, nuclear, electrical, GPE, Elastic potential & chemical measure in joules (J). Last 3 are stored.
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How can energy be transferred from one form to another?
An object above ground has GPE. A falling object transfers Gravitational Potential Energy to Kinetic Energy. Stretching elastic band chemical-->EPE. In Solar cell light-->electrical.
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What is the conservation of energy?
You cannot create/destroy energy. Total amount of energy always the same.
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What is a machine?
Something that transfers energy from one place/form to another. Useful energy in a machine is transferred to where & and in the form we want it.
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How can energy be wasted?
Wasted energy is not usefully transferred i.e. friction-heat in vehicles/machines.
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Give examples of how electrical appliances transfer energy into whatever form of energy we need?
Lamps, to produce light. Electric mixerskinetic energy. Speakers-->sound energy. TV-->light&sound.
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What is unit of power?
The watt (W). An appliance with power of 1 watt transfers 1 joule of energy per second. Kilowatts (kW) = 1000 watts.
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How do companies that supply main electrical measure the amount of energy used?
In kilowatt hours (kWh). kWh = kW (power of appliance) × h (time taken). Number of kWh × cost per kWh = total cost
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What are the costs you must consider when comparing the cost-effectiveness of different appliance?
Cost of: buying & installing appliance, running, maintenance, environmental, interest charged in a loan to buy appliance
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What is the payback time for an appliance?
Time it takes for appliance/installation to pay for itself in terms of energy savings.
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How does wind energy work + disadvantages?
The wind rotates the blades of a wind turbine driving a generator at the top of a tower. Requires many large turbines. Unreliable-wind doesn’t always blow.
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What happens at a hydroelectric power station + disadvantages?
Water is collected at a reservoir, is allowed to flow downhill and turn turbines at the bottom of a hill. Only works in wet/hilly areas. Damming causes flooding + affects local ecology.
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What happens in a pumped storage system?
Surplus electricity is used in times of low demand to pump the water back up the hill to the top reservoir so that it can be released to fall in times of high-demand.
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How can you use the movement of the waves to generate electricity + disadvantages?
The movement drives a floating turbine that turns a generatorelectricity is delivered to the grid system on shore by cable. Can be a hazard to boats + unreliable.
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How can tides (sea level rising & falling twice a day) be used to generate electricity + disadvantages?
The water at each tide can be trapped behind a barrage built across a river estuarywater is released to fall down to the lower sea level driving turbines. Few estuaries are suitable + barrage affects local ecology.
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What can a solar cells do and what can they do joined together?
Produce a small amount of energy (i.e.calculators, watches etc) by transferring solar into electrical energy. Joined forms solar panel. Water flowing through solar panel heated directly by solar energy.
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How can a solar power tower be used?
Thousands of mirrors used to reflect sunlight onto a water tank to heat the water & produce steam.
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How is geothermal energy produced + disadvantages?
Inside the earth by radioactive decay & heats surrounding rock. In volcanic areas deep holes are drilled & cold water is pumped down to the hot rocks coming back as steam used to drive turbine that turn generators = electricity. Drilling=difficult +
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What are the common pros and cons of Coal, Oil and Gas?
Reliable but non-renewable & produces CO2 (greenhouse gas) & SO2 (acid rain)
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What are the common advantages of all renewable energy resources?
No production of polluting gases + Free energy resource. Also Falling water = reliable in wet areas. Tides = reliable, always tides twice a day. Solar = Reliable in hot countries.
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Why does the National Grid use step up and step down transformers?
As transmission at high voltage reduces the energy wasted in the cables, increasing efficiency. The step down transformers are used to decrease voltage so that it’s safe for consumers.
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What are the advantages and disadvantages of overground cables?
Overhead: pros: Easy to access, less expensive to install, cables cooled by air, can use thinner cables Cons: spoils the landscape, greater risk of (fatal) electric shock, damaged by (severe) weather + hazard to helicopters.
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What are the advantages and disadvantages of underground cables?
Underground: pros: cannot be seen, no hazard to helicopters, not damaged by weather, no shock hazard. Cons: more expensive to install & repair, difficult to access, thicker cables, cooling systems + layers of electrical insulation required.
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What is the difference between the two types of wave (transverse + longitudinal)?
The oscillation / vibration of transverse wave perpendicular to the direction of energy transfer + for a longitudinal wave is parallel to the direction of energy transfer. Longitudinal waves made up of compressions and rarefactions.
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What are electromagnetic and mechanical waves?
Electromagnetic waves are transverse + can travel through a vacuum. Mechanical waves (longitudinal/transverse) travel through a medium (substance).
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What is the amplitude, wavelength & frequency of a wave?
Amp = height/depth of wave crest/trough from position at rest + volume. Wavelength = distance from 1 crest to the next. Frequency (Hz) = number of waves per second + pitch.
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What are the characteristics of the image in a plane mirror?
It is: the same size as the objects, upright, the same distance behind the mirror as the object is in front & is virtual.
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Compare a real image and a virtual image.
A real image is one that can be formed on a screen, because the rays of light that produce the image actually pass through it whilst a virtual image can’t be formed on a screen as the rays of light that produce the image only appear to pass through.
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What is refraction?
A change in speed of the waves causes a change in direction when they cross a boundary between two substances i.e. air & glass/water.
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What happens when a light ray enters a less/more dense substance?
More dense = slows down, ray changes direction towards the normal. Less dense = speeds up, ray changes direction away from normal but doesn’t change direction if travelling along a normal.
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What is dispersion?
When a ray of white light is shines through a triangular glass prism & produces spectrum. Violet light refracts the most. Red light refracts the least.
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What is diffraction?
Spreading of waves when passing through a gap/round an obstacle. The narrower the gap the greater the diffraction. i.e. if tv signal is blocked by a hill it will be poor if the radiowaves don’t diffract enough. Hard flat surfaces reflect sound-echoes
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What is sound caused by?
Mechanical vibrations in a substance & travels as longitudinal waves but can’t travel through a vacuum.
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How can you see the difference in waveform?
On an oscilloscope. Tuning forks produce ‘pure’ waveforms. Different instruments produce different waveforms.
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What is the order of waves in wavelength and frequency in the electromagnetic spectrum?
Radio (longest wavelength + lowest frequency), microwaves, Infrared, Light, Ultraviolet radiation, X rays, Gamma rays (shortest wavelength + highest frequency).
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What is visible light?
Part of electromagnetic spectrum we can see. Wavelength increases across spectrum from violet to red.
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What are Microwaves & radiowaves used in?
Communications – Microwaves used to send signals to and from satellites and within mobile phone network + Radiowaves transmit radio/TV programs + carry mobile phone signals.
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How are radiowaves produced?
Alternating voltage applied to an aerial emits radiowaves with the same frequency as the alternating voltage. When the waves are received the produce an alternating current in the aerial with the same frequency as the radiation received.
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How is the radio and microwave spectrum divided?
Into bands. Different bands = different communication purposes. Shorter the wavelength the more info they carry, shorter their range, the less they spread out.
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What are Optical fibres?
Very thin glass fibres. Used to transmit signals carried by visible light or IR. Signals travel down the fibre by total internal reflection + can carry more info + more secure than radio/microwave transmissions.
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What is the Doppler Effect?
The wavelength + frequency of waves will have shifted (relative to the observer) from the original produced by the source. i.e. siren (moving away – lower pitch, toward-higher pitch)
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What happens when the source moves towards/away from the observer?
Away – observed wavelength increases & frequency decreases. Towards – observed wavelength decreases + frequency increases.
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What is the red shift?
Light observed from distant galaxies has been ‘shifted’ towards the red end of the spectrum (frequency has decreased & wavelength has increased). The further away the bigger the red-shift.
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What does the red shift suggest?
That distant galaxies are moving away from us & each other (universe expanding suggests that it started with a Big Bang at a small initial point) + the most distant are moving away the fastest.
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What is the only explanation for Cosmic Microwave Background Radiation (CMBR)?
CMBR would be the radiation produced by the Big Bang. As the universe expanded the gamma radiation would have become a lower energy radiation – microwaves of CMBR.
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What is blue-shift?
Galaxy moving towards us, seen by observing dark lines in the spectra from galaxies.
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Other cards in this set

Card 2


How does the surface of an object affect how much infrared radiation it emits & absorbs?


Dark matt surfaces = good absorbers + emitters of IR. Light shiny surfaces = Good reflectors + Bad emitters of IR

Card 3


How do solids conduct electricity?


Preview of the front of card 3

Card 4


Why are metals good conductors?


Preview of the front of card 4

Card 5


What are poor conductors?


Preview of the front of card 5
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What can reduce the rate of condensation?

increasing the temperature

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