Flashcards
GCSE Physics P7 (OCR) - Sun, and Stars
Cards in this deck (22)
- 1What do all hot object do?Emit a continuous range of electromagnetic radiation, whose luminosity and peak frequency increase with temperature.
- 2What is ionisation?The removal of electrons from atoms.
- 3What do spectral lines provide evidence for?The chemical elements present within the object investigated.
- 4Why is the volume of a gas inversely proportional to its pressure, at room temperature?Each collision with a wall causes a tiny force, Together, billions of collisions produce gas pressure. If the same amount of gas is compressed into a smaller volume, then the collisions will be more frequent, and so the pressure will be greater.
- 5Why do the pressures and volumes of a gas vary with temperature?The colder the environment, the less energy the particles have. So, they strike the walls less frequently, and with less momentum. This decreases the pressure.
If the pressure is to remain constant, the volume of the gas must decrease to compensate for the fact that the collisions are weaker and less frequent. - 6What is absolute zero?-273 K
- 7How do you calculate constants of a gas?= Pressure x Volume
= Pressure / Temperature
= Volume / Temperature - 8How does a protostar form?1) A cloud of gas and dust is pulled together by gravity. It breaks up into several smaller clouds, and each continues to contract.
2) Within a contracting cloud, each particle attracts each other particle, so that the cloud collapses towards its centre. It forms a rotating, swirling disc.
3) As the particles are attracted towards the centre, they move faster, which means the gas gets hotter.
4) Eventually, the temperature of this material is hot enough for fusion to occur, and a star is born. - 9What is nuclear fusion?The reaction of two hydrogen nuclei fusing together to form a helium nuclei because the strong nuclear force acts on them if they get so close together.
- 10How do you calculate the energy released during nuclear fusion?Energy = (Mass Lost x Speed of Light) ^2
- 11The more _______ the star, the _________ its core and the __________ the nuclei created by fusion.Massive
Hotter
Heavier - 12How is energy transported from core to surface in a star?By photons of radiation and by convection.
1) Radiation (photons) travels outwards through the radiative zone.
2) Convection currents arise in the convective zone, and they carry heat energy to the photosphere.
3) Electromagnetic radiation is emitted by the photosphere and radiates outwards through the solar atmosphere. - 13What is the Hertzsprung-Russell diagram?A plot of temperature and luminosity.
- 14Where is each type of star located on the HR Diagram?White Dwarfs: Bottom Left
Main Sequence: Across the middle
Giants: Top Right
Supergiants: Top, Top Right - 15Where does fusion occur in a main sequence star?In its core.
- 16When does a star leave the main sequence? What happens to it?When its core hydrogen runs out. It swells to become a red giant or supergiant and its photosphere cools.
- 17What happens in a red giant or supergiant?Helium nuclei fuse to make carbon, followed by further reactions that produce heavier nuclei such as nirtrogen and oxygen.
- 18What happens to a low-mass star?It becomes a red giant, which lacks the mass to compress the core further at the end of helium fusion. It then shrinks o form a white dwarf.
- 19What doesn't happen in a white dwarf?Nuclear fusion. So the star gradually cools and fades.
- 20What happens in a high-mass star?Nuclear fusion can produce heavier nuclei, including iron. When the core is mostly iron, it explodes as a supernova creating nuclei with masses greater than iron and leaving a dense neutron star or a black hole.
- 21What are exoplanets?Planets which are orbiting other stars.
- 22What is the evidence for exoplanets?a) Small dips in the brightness of a star indicate a planet passing in front of it.
b) The wobbling motion of a star is caused by the gravity of a planet.
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- GCSE Physics (P7) Flashcards on GCSE Physics P7 (OCR) - Sun, and Stars, created by Josh Price on 26/04/2015.
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