key facts, word equations and rules

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Electricity

  • Current is never used up.
  • Current and brightness are similar.
  • Current is the opposite to resistance- when one increases, the other decreases.
  • Current flows from the posotive terminal of the battery to the negative.
  • LDR- in the light- restitance decreases, in the dark- resistance increases.
  • Series and parrallel- usually parallel is more useful.
  • Short curcuit- wire has no resistance and can become a hazard.
  • Diodes- current can only flow in one direction.
  • Resistors- increases the resistance so a short curcuit does not occur or prevents a component over heating with too much current.
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Magnetism

  • Like poles repel- opposties attract.
  • Use bar magnet or iron fillings to observe magnetic field.
  • Pattern- out of north and into south
  • Magnetic materials- Nickel, iron, colbalt, steel.
  • Iron is a good temporary magnet used in electromagnets.
  • Steel is good permanent magnet.
  • Freely suspended, magnet aligns itself with Earth's north and south poles.
  • Current in coil creates an temporary magnet around soft iron core.
  • More current= increases strength of magnet.
  • Used in bells and scrap yards for extracting metals from non-metals.
  • Relay is magnetic switch.
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Earth

  • Spins on its axis once a day= 24 hours.
  • Axis it tilted at 23.5 degrees at its extreme- causes seasons.
  • One year= 365 and a quarter days- time for the earth to orbit the sun.
  • Moon is the only natural satellite of the earth- 28 days for one orbit.
  • Same side of the moon always faces earth.
  • Eclipses- Lunar- Moon goes into the earth's shadow, Solar- the moon blocks the sun from view of the earth.
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Space

  • The sun is the closest star to earth out of millions in our galaxy.
  • The sun is the centre of our dolar system.
  • Nuclear fisions provide the sun's energy.
  • Our solar system is made up of the sun, nine orbiting planets, comets, asteroids and moons.
  • Earth is the only known atmosphere that supports our life form.
  • Satellites are kept in orbit by planet's gravitational pull.
  • Moons are non-luminous and reflect the sun's light.
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Light

  • Light is faster than sound.
  • It travels in straight lines from a luminous source.
  • Objects around have different properties.
  • Opaque- does not let light through, causing a shadow.
  • Translucent- lets some light through, is blurred. causes a faint shadow.
  • Transparent- lets all the light through, causes barely any shadow.
  • Some objects reflect the light, however are not luminous.
  • Refraction- the bending of light in a boundary between two mediums and densties- changes direction.
  • Dispersion-  ehite light splitting into a spectrum.
  • Light is a form of energy.
  • A light that is invisible to the human eye is called ultraviolet.
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Sound

  • Slower than light.
  • Molecules vibrate and are carried to the ear by sound waves.
  • Different animals and humans have different audible ranges.
  • Cannot travel through a vacuum- unlike light-needs a substance to carry it.
  • Sound travels at different speeds in different mediums.
  • Reflection of sound is an echo.
  • A sound to high for humans to hear is ultrasound.
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