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
• 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)
• Units for quantities


  • Energy - Joules (J)
  • Speed - Meters per second (m/s)
  • Mass - Kilograms (kg)
  • Height - Meters (m)
  • Power - Watts (W)
  • Time - Seconds (s)
  • Charge - Coulombs (C)
  • Potential Difference - Volts (V)
  • Current - Amps (A)
  • Resistance - Ohms (Ω)
  • Density - Kilograms per meter cubed (kg/m³)
• System


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


  • Magnetic store
  • Kinetic store (moving object)
  • Thermal store (hot object)
  • Gravitational potential store (raised against gravity)
  • Chemical store (in bonds)
  • Elastic potential store (stretched object)
  • Electrostatic store (attraction between positive and negative objects)
  • Nuclear store
• Energy can be transferred between these stores in four ways: heating, mechanically, electrically, and by radiation
• 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 (mass, gravitational field strength, height)

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


  1. Write down the equation

  2. Substitute the values (mass, velocity)

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

  1. Write down the equation

  2. Substitute the values (spring constant, 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, per kilogram and per degree Celsius
• Calculating specific heat capacity

  1. Write down the equation (change in energy = mass x specific heat capacity x change in temperature)

  2. Substitute the values (energy, mass, temperature change)

  3. Rearrange to solve for specific heat capacity and include the units (Joules per kilogram degree Celsius)
• The required practical is to find the specific heat capacity of a metal block or liquid
• 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


  Generated faster than used
• Non-renewable/finite energy resources


  Used faster than generated
• Factors to consider for each energy resource

  • Renewable/non-renewable
  • Cost
  • CO2 emissions
  • Reliability
  • Geographic restrictions
  • Radioactive waste disposal and risks (for nuclear)
• Need to know all circuit symbols and be able to draw circuits properly
• Current


  Speed of flow of charge around circuit
• Potential difference


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

  1. Use ammeter in series, voltmeter in parallel

  2. Calculate resistance using R=V/I

  3. Compare resistance of wires of different lengths and resistors in series/parallel
• Required practical 16 - Investigate current and potential difference for circuit components


  1. Use ammeter in series, voltmeter in parallel

  2. Draw IV graphs for different components
• IV graphs

  • Ohmic conductor - linear, proportional
  • Filament lamp - S-shaped curve, resistance increases with temperature
  • Diode - only allows current flow in one direction, small potential difference before current starts
• 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
• In series circuits


  Potential difference split between components