Term
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Definition
*all objects emit radiation
*the hotter the object the more it emits
*heat radiation can travel through a vacuum eg space this is why we get heat from sun
*part of electro-magnetic spectrum |
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Definition
*dark matt surfaces absorb heat and become hotter than shiny white surfaces
*dark matt surfaces are good emitters so a dull black surface cools down quicker a than shiny white surfaces |
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Definition
*occurs mainly in solids
*is mainly due to free electrons transfering energy
*metals = good conductor non-metals = poor conductor
*fibre glass = good insulators as they contain trapped pockets of air |
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Definition
*takes place only in liquids and gases
*when fluid heated it expands becomes & less dense and rises
* convection current transfers heat throughout the fluid
Convection currents are resposible for on and offshore breezes |
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Term
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Definition
*large surface area loses heat more easily
*small objects lose heat more easily than large objects
*heat loss from building can be reduced using alluminium foil behind radiators,cavity wall insulation,double glazing and loft insulation =saves money |
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Term
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Definition
energy can change from 1 to another but always set amount of energy overall
eg light, thermal, sound, kinetic,
nuclear, electrical, gravitaional potential, elastic potential, chemical |
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Term
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Definition
useful energy is in the form needed
wasted energy is not needed
eg heat from a light bulb
useful and wasted end up in surroundings |
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Term
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Definition
efficiency = useful energy/input energy
unit is Joule (J)
x by 100 to get percentage |
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Term
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Definition
electrical energy is energy transferred due to electric current
commonly used as easily tranferable |
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Term
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Definition
power = energy transferred/
time taken
power is the rate at which a device transforms energy
1KW = 1000W |
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Term
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Definition
network of cabels and transformers
step up transformers to step up to power station voltage to national grid voltage eg 25 to 132 KW or more
step down transformers to step down voltage for use in homes 240V |
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Term
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Definition
*In power stations water is heated to make steam which drives the turbine which power the generators
*In nuclear power station uranium undergoes nuclear fission which releases energy which drives turbine which gives energy to generator which forms electricity |
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Term
| energy from wind and water |
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Definition
wind passes over blades which rotate to drive generator
water collected in reservoir flows downhill and turns turbine at bottom (hydroelectric)
movement of waves on sea can be used to generate electricity
changes in tides can be used to build barrage to keep water back and then when released to fall down it will drive turbine |
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Term
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Definition
travels to earth as electromagnetic radiation.
A solar cell transforms this to electrical energy.
single cells used to power calculator. Large solar panels are numbers of cells joined together to give more power.
Water flowing through solar panel is heated directly by sun. |
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Term
| energy form the enviroment |
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Definition
coal oil gas are not renewable resources
*are all reliable but produce CO2 a greenhouse gas
Oil and coal also produce SO2 causes acid rain
Nuclear fuel reliable but produces nuclear waste and risk of accident |
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Term
wind ,falling water, waves,
tides, solar, geothermal |
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Definition
all renewable and free but not reliable
wind-costly large turbines
falling water only can work in wet hilly areas
using waves for energy-hazards to boats
using tides -only few rivers suitable
solar -only suitable for small amounts of electricity |
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Term
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Definition
electromagnetic radiation travel as waves.
travels through space
grouped according to frequency and wavelength |
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Term
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Definition
gamma -shortest wavelength, highestfreq
radio waves -longest wavelength, lowest freq
wavespeed = frequency x wavelength
frequency measured in Hertz |
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Term
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Definition
gamma used to sterilise surgical instruments and keep food fresh by killing bacteria
x rays used to shadow pictures of bones
both mostly pass through soft body tissue but some will be absorbed and damage cells.
Can cause changes in cells and make them
cancerous. |
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Term
| light and ultraviolet radiation |
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Definition
ultraviolet radiation has longer wavelength than x rays but shorter wave length than visible light
It damages skin cells and over exposure can damage eyes |
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Term
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Definition
given out by all objects.
The hotter the object the more it emits
night vision works by detecting infra red
it is absorbed by skin, sensed as heat.
used as heat source in toasters and grills |
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Term
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Definition
used for cooking and communications
heat the water in food heating it from inside out
the water in living cells will absorb microwaves and maybe damage or killed by the heat released
microwave transmitters produce wavelengths to pass through atmosphere to send signals within mobile phone networks and to satelites |
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Term
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Definition
used to transmit radio and TV programmes
alternating voltage applied to aerial which emits radiowaves with same frequency as alternating voltage.
When received they produce current with same frequency |
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Term
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Definition
microwave and radio wave are used for communications TV, mobile phones and radio.
different frequencies are used
visible light and infra red radiation are used to carry signals in optical fibres by continuous reflections. |
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Term
| analogue and digital signals |
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Definition
analogue signals vary continuously in amplitude.
digitial signals are either high (1) or low (0)
Digital is free of noise and distortion as it is still clear even when it travels over distances because it only takes values high or low. |
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Term
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Definition
radioactive substances are unstable, they emit alpha, beta or gamma rays to become stable.
This is radioactive decay. |
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Term
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Definition
helium nucleus
2 protons 2 neutrons
relatively large so have lots of collisions
they can be stopped by a this sheet of paper.
They are positively chargedand are deflected by electric and magnetic fields |
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Term
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Definition
high speed electron from nucleus emitted when a neutron changes to a proton and at same time emits an electron
They are much smaller and faster and penetrate further
Blocked by air or shhet of alluminium
negatively charged and deflected by electric and magnetic fields |
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Term
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Definition
electromagnetic waves which travel a long way through material
several cm of lead or concrete needed to absorb the radiation
not deflected by electric or magnetic fields |
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Term
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Definition
| time taken for the number of atoms (and mass) to be halved |
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Term
| uses of alpha,beta, gamma radiation |
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Definition
alpha used in smoke alarms
beta used in manufacture of paper
gamma used as tracers in medicine (swollowed or injected and used to trace progress around body)
gamma used to sterilise medical instruments and keep food fresh |
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Term
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Definition
light from distant galaxy is red-shifted to longer wavelengths
the further away the bigger the red shift |
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Term
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Definition
| a collection of millions of stars |
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Term
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Definition
| change of frequency of light towards red end of spectrum |
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Term
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Definition
red shift provides evidence that galaxies are moving away the furhtest are moving away the fastest which is evidence of expanding universe in all directions
The universe started with BIG BANG a massive expolsion from a small point |
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Term
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Definition
telescopes and satellites are able to receive all types of electromagnetic radiation from space so we can observe stars that are far away
The earths atmosphere is a layer of gases surrounding the earth |
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