Physics Paper 1

• Types of error


  • Systematic errors
  • Random errors
• Systematic errors are caused by poorly calibrated equipment
• Random errors could be caused because your equipment isn't sufficiently precise or just because of natural fluctuation in the true value of that quantity
• The way that we take account of this is that we make multiple readings and then we use those readings to calculate a mean
• Appendix 9 of the specification gives you a full list of everything that can be assessed for any of the base units
• Prefixes for units


  • Milli (1/1000)
  • Micro (1/1,000,000)
  • Nano (1/1,000,000,000)
  • Kilo (1,000)
  • Mega (1,000,000)
  • Giga (1,000,000,000)
• One of the first things I would always suggest you do in the first few minutes of the physics exam when you're just getting your head straight is to scribble down on the equation sheet what the units are for the different quantities
• Units for quantities


  • Energy (Joules)
  • Speed (Meters per second)
  • Mass (Kilograms)
  • Height (Meters)
  • Power (Watts)
  • Time (Seconds)
  • Charge (Coulombs)
  • Potential difference (Volts)
  • Current (Amps)
  • Resistance (Ohms)
  • Density (Kilograms per meter cubed)
• System


  An object or a group of objects that can store energy
• Ways energy can be stored in a system

  • Magnetic store
  • Kinetic store
  • Thermal store
  • Gravitational potential store
  • Chemical store
  • Elastic potential store
  • Electrostatic store
  • Nuclear store
• Conservation of energy


  In a closed system, energy cannot be created or destroyed, only transferred between different stores
• Calculating gravitational potential energy


  1. Write down the equation

  2. Substitute the values for mass, gravitational field strength, and height

  3. Calculate the answer and include the units (Joules)
• Calculating kinetic energy


  1. Write down the equation

  2. Substitute the values for mass and speed

  3. Calculate the answer and include the units (Joules)
• Calculating elastic potential energy

  1. Write down the equation

  2. Substitute the values for spring constant and extension

  3. Calculate the answer and include the units (Joules)
• Specific heat capacity


  The maximum amount of energy that a substance will absorb to make it change temperature by 1 degree Celsius per kilogram
• Calculating specific heat capacity

  1. Write down the equation

  2. Substitute the values for change in energy, mass, and change in temperature

  3. Calculate the answer and include the units (Joules per kilogram degree Celsius)
• The idea of the required practical is that you're given either a metal block or a container of liquid and you're trying to find out what the specific heat capacity is
• Change in temperature


  Difference between starting and ending temperature
• Mass


  Must be in kilograms (if given in grams, divide by 1000)
• Specific heat capacity


  How much energy it takes to heat up 1 kg by 1 degree C
• Required practical to find specific heat capacity

  1. Given metal block or container of liquid

  2. Use balance to measure mass

  3. Insulate to minimize energy losses

  4. Use thermometer to measure temperature change

  5. Use electrical heater to heat up

  6. Calculate energy transferred using voltmeter, ammeter, and stopwatch
• Power

  Rate at which energy is transferred or work is done
• More powerful appliance


  Faster it can do work or transfer energy
• Calculating power


  Energy (in joules) divided by time (in seconds)
• Efficiency


  Proportion of energy that has been usefully transferred, can be expressed as decimal or percentage
• Conservation of energy - same amount of energy at end as start, but some transferred wastefully
• Ways to reduce wasted energy

  • Reduce heat loss by insulating
  • Reduce thermal conductivity
  • Reduce drag by streamlining
  • Reduce friction
• Renewable energy resources


  Being generated faster than used
• Non-renewable/finite energy resources


  Being used faster than generated
• Factors to consider for energy resources

  • Renewable/non-renewable
  • Cost
  • CO2 emissions
  • Reliability
  • Geographic restrictions
  • Radioactive waste disposal and risks (for nuclear)
• Circuit symbols


  • Need to know all of them, draw circuits using ruler with no gaps
• Current


  Speed of flow of charge around circuit
• Potential difference


  Amount of energy being transferred by a component
• Required practical 15 - Measuring IV characteristics


  1. Use ammeter in series, voltmeter in parallel to measure current and potential difference

  2. Calculate resistance using R=V/I
• Required practical 16 - Investigating current and potential difference for circuit components

  1. Use ammeter in series, voltmeter in parallel to measure current and potential difference

  2. Draw IV graphs
• IV graphs


  • Ohmic conductor - linear, proportional
  • Filament lamp - S-shaped curve
  • Diode - only allows current flow in one direction
• Light dependent resistor


  Resistance decreases as light gets brighter
• Thermistor


  Resistance decreases as temperature increases
• Series circuits


  • Only one path for charges, current same everywhere
• Parallel circuits


  • Charges split at junction, currents in branches add up to total