Physics: Structured Paper P3 - Topic 5

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Kinetic Theory and Temperature in Gases

Gases are randomly moving particles!
> Very Small Particles
> Constantly Moving
> Collide with eachother all the time

Absolute Zero is as cold as stuff can get - 0 Kelvin
COLDEST EVER = -273 KELVIN
To convert from C to K just add 273. :)

Kinetic Theory is proportional to Temperature
The temperature of a gas (in kelvins) is proportional to:
the average kinetic energy of its particles. 

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Pressure in Gases

Constant = Pressure ÷ Temperature (in K)

p1/t1 = p2/t2 

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Particles In Atoms

ALPHA:

  • HELIUM NUCLEUS
  • SLOW AND HEAVY
  • STRONGLY IONISING
  • STOPPED BY PAPER

BETA:

  • AN ELECTRON
  • LIGHT AND FAST
  • MODERATELY IONISING
  • STOPPED BY THIN METAL

GAMMA:

  • ELECTROMAGNETIC RADIATION
  • NO MASS, VERY FAST
  • WEAKLY IONISING
  • STOPPED BY THICK LEAD 
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Different types of Radiation

POSITRON RADIATION= positively charged beta radiation

NEUTRON RADIATION= neutrons - very penetrating!

NEUTRONS ARE DIFFICULT TO DETECT BECAUSE THEY'RE NEUTRAL.
HERES WHY:

  • Charged particles knock electrons off atoms, ionising them.
  • LOSS OF ELECTRONS = IONISING
  • They also move towards charged objects.
  • You can use an electrical field to deflect a beam of alpha particles.
  • NONE OF THIS WORK FOR NEUTRONS- they are detected by looking for nuclear decays. 
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Particles in Atoms

A nucleus will be unstable if it has:

  • too many neutrons/too few neutrons
  • if its too heavy eg. to many protons and neutrons together
  • too much energy

β - ) decay happens when there are too many neutrons, the proton number decreases by one, and the nucleon number stays the same.

β + ) decay happens when there are too few neutrons, the proton number decreases by one, and the nucleon number stays the same.

α ) decay happens in heavy nuclei, the proton number decreases by two, and the nucleon number decreases by four.

γ ) is emitted from a nuclei with too much energy.

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Fundamental and Other Particles

Electrons and Positrons are fundamental particles.
This means you can't divide them into smaller particles.

Scientists can recreate fundamental particles by colliding particles at a very high speed. This produces an equal amount of matter and anti-matter made of anti-particles.

Each particle has an anti-particle which has the same mass, but opposite charge.

Protons and Neutrons are NOT fundamental particles.
They're made of quarks!!

Proton = UUD | Neutron = DDU

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Electron Beams

USED FOR TV SCREENS >>>

  • The heater heats the cathode and gives energy to the electrons.
  • They're pulled towards the positive anode.

Calculating the kinetic energy of each electron..

kinetic energy (j) = charge of electron (in coulombs) x accelerating voltage (volts) 

and, the size of the current produced..

current (l) = charge (n x e) ÷ time (t)

(http://personal.ee.surrey.ac.uk/Personal/S.Worrall/images/tv_set.gif)

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Electron Beams 2

An electron beam is attracted by a positive charge, and repelled by a negative charge.

Electron guns are used in TV's, Oscilloscopes, and to make X-Rays.

An Oscilloscope is a device for displaying the voltage and frequency of an electrical signal.
> = time / ^ = voltage 

xrays = tungsten target.

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