physics paper 1

• 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)
  • 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 (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)
  • Nuclear store
• Conservation of energy

  In a closed system, energy cannot be created or destroyed, only transferred between 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 by 1 degree Celsius per kilogram
• 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. Calculate the specific heat capacity and include the units (Joules per kilogram degree Celsius)
• 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 energy resources

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

  • Ohmic conductor - linear, proportional
  • Filament lamp - S-shaped curve, resistance increases with temperature
  • Diode - only allows current flow in one direction, small PD 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 splits between components
• In parallel circuits

  Each component gets full potential difference
• Electrical circuit

  1. Current splits into branches

  2. Current in branches adds up to total current

  3. Potential difference splits between components in series

  4. Potential difference is full for each component in parallel

  5. Total resistance in series is sum of individual resistances

  6. Total resistance in parallel is less than smallest individual resistance
• Alternating current (AC)


  Current that repeatedly changes direction, 50 times per second in UK
• Direct current (DC)


  Current that only flows in one direction
• UK main electricity supply frequency is 50 hertz
• UK main electricity supply potential difference is 230 volts
• Three-core cable and three-pin plug

  • Outer insulating plastic
  • Pins made of copper alloy (brass)
  • Live wire (brown)
  • Neutral wire (blue)
  • Earth wire (green and yellow)
• Fuse


  Thin metal wire that melts if too much current flows, breaking the circuit