Physics

• smoke alarms, smoke enters detector, alpha particles ionise in the air and those particles move across the gap, forming the current. Smoke in machine will absorb alpha particles and current will fall and siren will sound. the detector will sense the amount of current
• Use voltmeter to measure potential difference across the bulb. Use ammeter to read current. Record values in a table. Adjust variable resistor and record new readings on the voltmeters and ammeter. Repete to get range of readings. Switch battery direction, so now the potential different has reversed. Both voltmeter and ammeter now have negative values. Take several readings. Plot all readings on a graph
• Alpha:

  travel around 5cm in air

  can be stopped by a single sheet of paper

  very strongly ionising
• beta:

  can travel 15cm in air

  can be stopped by a few mm or aluminium

  quite strongly ionising
• gamma

  can travel several meters in air

  can be stopped by several cm of lead

  weakly ionising
• What is the specific heat capacity of a substance?

  Energy required to raise 1 kg by 1°C
• Why is determining the specific heat capacity of a material important?

  It is a required practical for exams
• What material's specific heat capacity are we determining in this practical?

  Vegetable oil
• What is the first step in the practical procedure?

  Place a beaker on a balance and zero it
• What do we record after adding oil to the beaker?

  The mass of the oil
• What is the purpose of wrapping the beaker in insulating foam?

  To reduce thermal energy transfer to surroundings
• What device measures the electrical energy passing into the immersion heater?

  A joule meter
• What information do we need to calculate the specific heat capacity?

  Total energy, mass, and temperature change
• How long do we leave the setup for the temperature to rise?

  Around 30 minutes
• What is the equation for calculating change in thermal energy?

  Change in thermal energy = mass × specific heat capacity × temperature change
• What were the results of the experiment for the specific heat capacity calculation?

  0.95 kg heated from 20°C to 75°C
• How do you rearrange the equation for specific heat capacity?

  Specific heat capacity = change in thermal energy / (mass × temperature change)
• How much electrical energy passed into the immersion heater?

  87258 joules
• What is one reason the specific heat capacity may not be accurate?

  Thermal energy passing out of the beaker
• What can be done to ensure all thermal energy passes into the oil?

  Ensure the immersion heater is fully submerged
• How can we prevent incorrectly reading the thermometer?

  Use an electronic temperature probe
• How can we reduce thermal energy loss to the air?

  Use an insulator with lower thermal conductivity
• What can be done to ensure thermal energy spreads through the oil?

  Stir the oil
• What are the steps to determine the specific heat capacity of a material?

  1. Zero the balance with the beaker.
  2. Add oil and record its mass.
  3. Insert thermometer and immersion heater.
  4. Measure starting temperature.
  5. Wrap beaker in insulating foam.
  6. Connect joule meter and power pack.
  7. Wait for 30 minutes.
  8. Record total energy and final temperature.
  9. Calculate specific heat capacity using the formula.
• What should you expect in your exam regarding this practical?

  Questions on the required practical
• What are the main sources of inaccuracies in the specific heat capacity experiment?

  • Thermal energy loss to air
  • Incomplete energy transfer to oil
  • Incorrect thermometer readings
  • Uneven thermal energy distribution in oil
• What is the main goal of the experiment described?

  To investigate the effectiveness of thermal insulators
• Why is this experiment important for triple physics students?

  It is a required practical for their studies
• What are the steps to compare different thermal insulators?

  1. Place a small beaker inside a larger beaker.
  2. Boil water and transfer 80 cm³ to the small beaker.
  3. Use cardboard as a lid with a hole for a thermometer.
  4. Record the starting temperature and measure every 3 minutes for 15 minutes.
  5. Repeat with different insulating materials.
• What volume of hot water is used in the experiment?

  80 centimeters cubed
• What is the purpose of the cardboard lid in the experiment?

  To cover the beaker and hold the thermometer
• How often should the temperature be recorded?

  Every three minutes
• What is the independent variable in this experiment?

  The type of insulating material used
• What is the dependent variable in this experiment?

  The temperature of the water
• What are control variables in this experiment?

  Volume of water and mass of insulating material
• Why is it important to keep the starting temperature the same?

  To ensure fair testing and accurate results
• How can cooling curves be used in this experiment?

  • Plot temperature against time for each insulator.
  • Determine which insulator retains heat best.
  • Compare the effectiveness of different materials.
• How does the thickness of a material affect thermal insulation?

  More layers provide better insulation
• What is the independent variable when testing layers of newspaper?

  The number of layers of newspaper
• What is the dependent variable when testing layers of newspaper?

  The temperature of the water