physics unit one

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  • Created by: beki28
  • Created on: 23-05-16 18:37
what's thermal radiation?
transfer of heat energy by electromagnetic waves
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bigger temp difference, ......
faster heats transferred
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what does an object that's hotter than its surroundings do?
emits more radiation than it absorbs
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what does an object that's cooler than its surroundings do?
absorbs more radiation than it emits
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what does heat radiation depend on?
surface area
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bigger the surface area, ......
more waves emitted from surface = quicker transfer of heat
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dark matt surfaces do what?
absorb heat radiation, emit much more than shiny silver
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what is conduction of heat?
process where vibrating particles pass on their extra kinetic energy to neighbouring particles
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metals in heat conduction
conduct heat better than plastic or wood, due to free electrons
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why do metals conduct well?
electrons are free to move
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what's an example of a good conductor?
copper
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when does convection occur?
when more energetic particles move from hotter region to cooler, taking heat with them
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what's the immersion heat example?
1) heat transferred from heater coils to water 2) particles near coils get more energy, move around faster 3) density reduces, hotter water rises above denser water 4) hot water rises, displaces colder water, making it sink towards heater coils
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describe the thermos flask
1) glass bottle = double-walled, vacuum between them 2) walls = silvered, keep heat loss by radiation to minimum 3) bottles supported using insulating foam = minimises heat conduction 4) stopper = plastic, filled with foam to reduce heat conduction
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what's the principle of the conservation of energy?
energy can never be created nor destroyed, it's only ever converted from one form to another
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what's useful input energy lost as?
heat
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less energy wasted, .......
more efficient device is
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what are the factors that need to be considered when choosing a device?
1) initial cost 2) running cost 3) how often need repairing or replaced 4) ease of use 5) looks
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what do batteries convert?
chemical energy to electrical
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what doe electrical devices convert electrical energy into?
sound, light and heat
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what does cavity wall insulation do?
reduces convection and radiation across gaps
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what does lost insulation do?
reduces conduction and radiation into roof from ceiling
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what does draught proofing do?
reduces heat loss due to convection
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what does double glazing do?
more radiation reflected back, air gap between layers reduces conduction
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what do thermostatic radiator valves do?
prevent house being over-warmed
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what does a hot water tank jacket do?
reduces conduction and radiation
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what does the national grid do?
takes electrical energy from power stations to where it's needed in homes and industry
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what's a problem with a high current?
lose loads of energy through heat in cables
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what do transformers do?
step voltage up at one end, for efficient transmission, then bring back down to safe, useable levels at other end
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what are non-renewable energy sources?
3 fossil fuels - coal, oil and natural gas, and nuclear
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environmental problems of non-renewable energy
1) burning coal and oil releases sulfur dioxide, causing acid rain 2) coal mining = mess of landscape
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what are renewable energy sources?
wind, waves, tides, hydroelectric, solar, geothermal
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characteristics of renewable energy sources
1) never run out 2) damage environment 3) don't provide much energy 4) unreliable, depend on weather
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what do all waves have?
wavelength, frequency, amplitude and speed
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whats the order of the spectrum of EM waves?
radio, micro, infrared, visible light, ultra violet, x-rays, gamma rays
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describe sound waves
1) caused by vibrating objects 2) longitudinal waves 3) reflect and refract 4) higher freq, higher pitch
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what's the doppler effect?
1) freq moving towards, seem higher, wavelength shorter 2) freq moving away, seem lower, wavelength longer 3) longitudinal and transverse waves
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how did the Big Bang happen?
1) universe compressed into a very small space 2) exploded 3) expansion still happening 4) rate of expansion estimates age of earth, 14 billion years ago
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how do we work out payback time?
cost / savings per year
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common properties of EM spectrum
1) travels at the same speed in a vacuum 2) transfers energy/information from one place to another. 3) they are transverse waves.
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advantages of using optical fibres over copper cables
1) they require fewer boosters to increase strength of the signal 2) more difficult to bug (tap into) the signal 3) weigh less 4) use less energy
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what does ionising do?
energy in particles rip electrons away from atoms, forming ions that cause damage to DNA cells = some types of cancer
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what's alpha?
a helium nucleus (2 protons and 2 neutrons)
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what's beta?
fast moving electron
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what's gamma?
high energy electromagnetic wave
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when's radon gas formed?
uranium in volcanic rocks e.g. granite undergoes radioactive decay, forms radium, then radium decays to radon gas. high levels of radon gas can lead to lung cancer
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what evidence is there for the universe is expanding?
cosmological redshift – more distant galaxies have greater redshifts
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what evidence is there for large explosion (big bang) at the start?
CMB radiation is the red-shifted gamma rays produced by the Big Bang
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Other cards in this set

Card 2

Front

faster heats transferred

Back

bigger temp difference, ......

Card 3

Front

emits more radiation than it absorbs

Back

Preview of the back of card 3

Card 4

Front

absorbs more radiation than it emits

Back

Preview of the back of card 4

Card 5

Front

surface area

Back

Preview of the back of card 5
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