physics p1

• Radioactive decay


  Certain nuclei are unstable and will decay by emitting radiation
• Stable nucleus


  • Has the right amount of neutrons for the number of protons it has
• Unstable nucleus


  • Has too many or too few neutrons and will decay naturally
• Types of radioactive radiation

  • Alpha particle
  • Beta particle
  • Gamma ray
• Alpha particle


  A heavy particle consisting of 2 protons and 2 neutrons
• Alpha decay


  1. Atomic number decreases by 2

  2. Mass number decreases by 4
• Beta particle


  A fast moving electron emitted from the nucleus
• Beta decay


  1. Atomic number increases by 1

  2. Mass number stays the same
• Gamma ray


  High energy electromagnetic radiation emitted from the nucleus
• Gamma ray emission


  No change in atomic or mass number
• Ionising power


  The ability to convert an atom or molecule into a charged particle by adding or removing electrons
• Geiger-Muller tube


  Can detect all types of radioactive decay
• Half-life


  The time it takes for the number of nuclei of a radioactive sample to halve
• Count rate


  The number of decays recorded each second by a detector
• Resistors


  Components in an electric circuit that oppose or limit the current
• Resistors


  • Each resistor has a set resistance which does not change
  • Resistors come in different types, and may be fixed or variable
  • A variable resistor allows you to change the current in a circuit by changing its resistance
• Ohmic resistors


  Components that obey Ohm's Law, meaning their resistance does not change with the current
• Non-ohmic resistors


  Components that do not obey Ohm's Law, their resistance changes as the current changes