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P2
Physics GCSE
| Term | Definition |
|---|---|
| photocell | a flat silicon surface that captures light energy from the sun and transforms it into an electrical direct current |
| passive solar heating | when visible light and infrared radiation passes through glass into a room, is absorbed by objects, and re-emit longer wavelength IR radiation |
| dynamo effect | the way in which electricity can be generated by moving a wire near a magnet and vice versa |
| alternating current (AC) | an electric current that changes direction of flow repeatedly; produced by generators |
| direct current (DC) | an electrical current that only flows in one direction; produced by batteries |
| production of electricity in power stations | fuel burnt > water turned to steam > steam drives turbine > turbine turns generator > electricity produced |
| greenhouse gases | gases that trap heat and warm the earth; includes carbon dioxide, water vapour and methane |
| greenhouse effect | short wavelength EM radiation absorbed by earth > heats up > earth radiates longer wavelength IR radiation > greenhouse gases absorb these |
| step-down transformer | reduces voltage for safer use for consumers |
| step-up transformer | increasing voltage to decrease the current so that the wire doesnt heat up due to collisions and no heat is lost to the environment |
| electric current | the flow of electric charge from the power supply to the components in the circuit |
| cost of using an appliance for a certain length of time | total cost (p) = no. kilowatt hours used (kWh) x cost per unit (p) |
| formula for energy supplied (kWh) | energy supplied (kWh) = power (kW) x time (h) |
| background radiation | radiation that occurs naturally around us; comes from radioactive substances in rocks etc, and cosmic rays |
| ionisation | radiation that turns atoms into ions (charged particles)that can damage living cells |
| use of alpha radiation | in smoke detectors; they cause ionisation of air so small current flows - smoke absorbs alpha particles, current is reduced, alarm sounds |
| use of beta radiation | paper thickness gauge as beta particles are absorbed when passed through paper; used in tracers |
| use of gamma rays | used to treat cancer; it kills cancerous cells; also used in non-destructive tests |
| comet | small body w/ core of frozen gas (ice) and dust with trail of debris. have highly elliptical orbits around the sun |
| red shift | the shifting of wavelengths of light towards red end of the spectrum; e.g. further away a galaxy is, the greater the red shift (so they travel faster than those closer to us) |
| end stages of heavy-weight star | star > red supergiant > supernova > neutron star or black hole |
| end stages of medium weight star | star > red giant > planetary nebula > white dwarf |
| geocentric model | theory that the earth is the centre of the universe; suggested by ptolemy |
| copernican model | idea that planets sat on spheres, stars didnt move, the sun was the centre of the universe, earth rotated 24 hrs and earth takes 1 year to orbit the sun |
Created by:
nadiabacha
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