Triple Science P3 Flashcards

Flashcards that explain the hardest parts of P3 in the simplest way possible!

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An Electron Gun

Electron Gun Process:

  • An electric current (6V) is supplied to the filament (the coil of metal) to heat the cathode (negative electrode), giving energy to it's electrons. These start to heat up and vibrate.
  • Electrons then 'boil off' and escape the cathode. This process is called thermionic emission.
  • The negatively charged electrons are attracted to the anode, and accelerate towards it.
  • The anode channels the electrons and concentrates them into an electron beam.
  • The beam then fires past electrically charged parallel metal plates that deflect the electrons and bend the beam, reflecting them between the plates.
  • The beams have so much kinetic energy due to the concentration and speed of the fired electrons, they make a fluorescent screen glow and show the path of the beam.

    Important side-notes:

    Changing the voltage between the anode and the cathode OR the charged metal plates affects the path of an electron beam.
    Inside of the tube contains A VACCUM.

    When the heater current is increased, the number of electrons produced will INCREASE as well.

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  • Oscilloscopes are voltmetres that display how a voltage changes with time. They also show a real-time graph of how varibales (things that change) like temperature and pressure change over a period of time.
  • They are used commonly to monitor the condition of patients on hospital (as you see in Grey's Anatomy).
  • An electron gun in the oscilloscope fires electrons onto the screen to create an image.
  • Cathode Ray Tubes (CTRs) are tubes with a vaccum containing one or more electron guns. Before flat screen TV's, CRTs were used in televisions and computer monitors as well.
  • A voltage provides energy to the electrons flowing in an electric circuit.
  • To calculate kinetic energy, KE, gained by one electron fired from an electron gun, you use the equation:

KE = Electronic charge x accelerating voltage or

KE= e * V (where e= 1.6x10^-19 Coulombs)

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Absolute Zero

Absolute Zero

  • Absolute Zero is the lowest possible temperature an object could be.
  • Absolute Zero occurs at -273°C. Heat is generated via the movement of particles, and as they get slower, an object's temperature decreases. When the particles in an object come to a complete halt, they have no kinetic energy. The temperature -273­­°C is also called Zero Kelvin (or 0 K for short).
  • To convert a temperature in degrees Celcius into Kelvin, you just add on 273. Simple, right?
  • For example, 20°C = 293 K.

  • If you double the kelvin temperature, the average kinetic energy of the particles in a gas also doubles. Kelvin and the average kinetic energy of the particles are directly proportional. If you had a graph of Kelvin vs average kinetic energy, you would see a straight line.
  • If you were to measure temperatures below -200°C, you could not use a normal mercury thermometer. Instead, you would use a helium thermometer, as helium remains a gas down to -269°C.
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Pressuring Particles


  • On Earth, the particles contunually collide against eachother and exert atmospheric pressure. The amount of pressure there is depends on how 'tightly packed' the particles are.
  • In outer space, there is almost no pressure, while in the centre of a planet or star, there is a lot.
  • The atmospheric pressure you normally experience is about 10N/cm² (or 100kN/m²)
  • A way to increase pressure (the amount of collisions) is to increase the temperature. At a higher temperature, the molecules collide harder and more often. At higher temperatures there is a higher pressure.
  • The equation for a gas in a sealed container is:

Pressure, P (Pa)

_____________   = constant

temperature,t (K)

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Gas Laws (1)

Gas Laws

  • The volume of air in a balloon depends on the number of particles it contains, the temperature, and the pressure in the atmosphere outside of the balloon. A weather balloon can be used to take measurements as it rises through the atmosphere.
  •  As it gains altitude, the pressure drops more than the temperature decreases and the balloon expands. At 35km, the balloon expands so much that it bursts, returning to Earth by parachute, with a record of the different weather conditions at different altitudes.

In a graph that shows volume (cm³) over pressure (kPa), we see that volume and pressure are inversely proportional.


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Gas Laws (2)

Gas Laws

  • Volume is proportional to the kelvin temperature. If the kelvin temperature doubles the volume doubles, as long as the pressure does not change!

  • (
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Gas Laws(3)

Gas Laws (3)

The points on this slide are really important, so revise this bit carefully!

The volume of gas in a sealed container is:

  • Proportional to the Kelvin temperature (k). If T doubles, V doubles.
  • Inversely proportional to the pressure (P). If P doubles, V halves
  • From this, we can see that PV/T = constant

    The gas equation to work out pressure changes is:

  • P1 V1             P2 V2
    -----------    =   ---------
  •   T1                      T2

    T = KELVIN! NOT C!!!

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  • An oscilliscope bends an electron beam using charged deflection plates, but in a television tube electromagnets deflect the electrons.The evacuated ray tube (evacuated means in a vaccum) of a colour television is a lot more complex than that of an oscilliscope.
  • In an oscilli
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Thank you!

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