P1: conservation and dissipation of energy

    Cards (18)

    • Energy stores that could come up in the GCSE syllabus
      • Gravitational
      • Elastic
      • Electrostatic
      • Chemical
      • Thermal
      • Sound
      • Nuclear
      • Light
    • Energy can interchange between these different forms, but energy is always conserved - it cannot be created or destroyed, only changed in form
    • Energy changes in a swing set
      1. Gain gravitational potential energy
      2. Convert to kinetic energy
      3. Lose energy to friction (thermal)
      4. Possibly some sound energy
    • Energy changes in an iPod
      1. Chemical energy in battery
      2. Convert to sound
      3. Convert to light
      4. Produce thermal energy
    • Energy changes in an electric kettle

      1. Electrical energy from mains
      2. Convert to thermal energy
      3. Possibly some sound energy
    • Sankey diagram

      Quantitative representation of energy changes, with size of arrows representing amount of energy
    • Efficiency
      Useful energy output divided by total energy input, can be expressed as a percentage
    • Work done
      Energy transferred when a force causes an object to move, calculated as force x distance
    • Calculation triangle for work done
      • Work done = Force x Distance
      • Distance = Work done / Force
      • Force = Work done / Distance
    • Gravitational potential energy (GPE)
      Energy stored due to an object's position in a gravitational field, calculated as mass x gravity x height
    • Calculation triangle for GPE
      • GPE = Mass x Gravity x Height
      • Mass = GPE / (Gravity x Height)
      • Gravity = GPE / (Mass x Height)
      • Height = GPE / (Mass x Gravity)
    • Kinetic energy (KE)
      Energy of motion, calculated as 1/2 x mass x velocity^2
    • Calculation triangle for KE
      • KE = 1/2 x Mass x Velocity^2
      • Mass = 2 x KE / Velocity^2
      • Velocity = sqrt(2 x KE / Mass)
    • Elastic potential energy

      Energy stored in a stretched or compressed object, calculated as 1/2 x spring constant x extension^2
    • Calculation triangle for elastic potential energy
      • Elastic potential energy = 1/2 x Spring constant x Extension^2
      • Spring constant = Elastic potential energy / (1/2 x Extension^2)
      • Extension = sqrt(2 x Elastic potential energy / Spring constant)
    • Power
      Rate of energy transfer, measured in watts (joules per second)
    • Calculation triangle for power
      • Power = Energy transfer / Time
      • Time = Energy transfer / Power
      • Energy transfer = Power x Time
    • Efficiency = Useful power output / Total power input
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