Paper 1

• Alpha particles

  Helium Nuclei
• Alpha radiation is where alpha particles are emitted from the nucleus
• What is an alpha particle made of?


  Two neutrons and protons
• Alpha particles don't penetrate very far in materials and are stopped quickly
• Alpha particles are strongly ionising
• Alpha particles are absorbed by a sheet of paper, only a few cm in the air
• Beta particles

  High-Speed Electrons (e-)
• A Beta particle is simply a fast-moving electron released by the nucleus
• Beta particles have no mass and a charge of -1
• Beta particles moderately penetrate and moderately pass into materials before colliding, range in air of a few metres
• Beta particles are absorbed by aluminum (around 5mm)
• Every beta emitted, a neutron turns into a proton
• Gamma Rays

  EM Waves with a short wavelength
• Gamma rays are waves of electromagnetic radiation released by the nucleus
• Gamma rays

  • They penetrate for into materials without being stopped
  • They travel a long distance through air
  • They are weakly ionising because they pass though than collide, they hit something and do damage
  • They can be absorbed by thick sheets of concrete or Lead or metres
• Plum pudding model

  The positive charge is just one big thing with negative atoms inside it
• Nuclear model

  Protons and neutrons are attached to each other (nucleus) and electrons and their Shells orbit the nucleus
• Types of radiation

  • Alpha
  • Beta
  • Gamma
• Background Radiation


  Surrounding us and differs in levels of danger to the body in everyday life (e.g. food, rock)
• Irradiation

  When an object is exposed to radiation. The object does not become radioactive.
• Contamination

  Unwanted radiated atoms entering objects. Use tongs or gloves. Use lead-lined boxes.
• Nucleus

  The centre of an atom where protons and neutrons are found
• Ionising


  Removing electrons in atoms. Causes damage to DNA that could cause cancer.
• Isotope

  An atom with the same number of protons but a different number of neutrons
• Radioactive Decay

  When an unstable nucleus releases radiation to become more stable. Random.
• Half-Life

  The time taken for the number of radioactive nuclei or count rate to half the original value
• What is conduction?

  - Conduction is the transfer of heat or electricity through a material (solid) by direct contact.

  • Heat transferred to its KE store
  • > vibrates faster
  • >therefore collide with other particles more
  • >until heat spread out evenly
• What is convection?

  Convection is the transfer of heat through the movement of a fluid, such as air or water.
• Specific Heat capacity (practical)

  1. Place beaker on a balance with zero
  2. Add oil and record mass
  3. Add immersion heater and thermometer > read starting temp
  4. Wrap beaker in insulating foam
  5. Connect joulemeter to immersion heater with power pack
  6. Time 30 mins > read joulemeter and record final temp
• How to measure density (regular object)?

  1. Determine mass of regular object using balance
  2. To work out volume, use a ruler and measure its sides (e.g cube)
  3. Calculate Density

  Density = Mass/ Volume
• How to measure density (irregular object)

  1. Find the mass of an object using a balance
  2. Fill a eureka can with water
  3. Place object in the can and water shall flow out of the spout
  4. Measure volume by the water being flowed into measuring cylinder
  5. Calculate Density

  Density = Mass/Volume
• Thermal Insulation (Practical)

  1. Place small beaker inside of a large beaker
  2. Transfer 80cm (cubed) of water into the smaller beaker > Add cardboard as a lid with a small hole
  3. Place a thermometer in the cardboard lid
  4. Use stopwatch and record starting temp - record temp every 3 min for 15 mins
  5. Next repeat practical with different insulating materials
• Parallel circuit

  • Current DIVIDES at the point it branches then recombined
  • Potential Difference across each loop is the SAME as the P.d across the battery

  
• Static electricity

  • Polythene rod = Electrons gained by rod = Negatively charged
  • Perspex rod = Loss of electrons = Positively charged
• Ohms Law:

  Resistance stays constant and is not affected by potential difference and current
• Ohmic devices

  Thermistors, fixed resistors and LDRs (Light dependent resistor)
• I - V Characteristics


  This is:

  
• Non - Ohmic Devices

  This is:

  
• Accuracy vs Precision

  Accuracy: How close a given set of measurements are to the true value

  Precision: How close the measurements are to one another
• The national grid + Transformers

  The national grid is a system of cables and transformers that link power stations to consumers

  Step-up Transformers = Increase P.d and decrease Current

  Step-down Transformers = Decrease P.d and increase current

  Cables are thick and have high potential difference > minimise power lost