Energy

• Name the 8 energy stores.

  Kinetic,

  Gravitational potential,

  Elastic potential,

  Thermal,

  Chemical,

  Nuclear,

  Magnetic,

  Electrostatic.
• Name the 4 ways energy can be transferred.

  Heating,

  Waves,

  Electric current,

  Mechanical (force).
• What is the law of conservation of energy?

  Energy cannot be made or destroyed, only made between stores.
• What is a closed system?

  A system where no energy can be transferred in or out - (total energy of system stays the same).
• What is work done?

  Energy transferred when a force moves an object.
• What is energy transfer when a moving car slows down?

  Kinetic - thermal (brake)

  - thermal (surroundings)
• What is the energy transfer when a kettle is used to heat water?

  Electric - thermal (heating element) - thermal (water)

  - thermal (surroundings)
• What is the energy transfer of a falling object?

  Gravitational potential - kinetic

  - thermal (surroundings)
• What is wasted energy?

  Energy that has transferred into an unwanted energy store.
• What happens to wasted energy?

  It spreads out (dissipates) into the surroundings.
• How do you calculate the efficiency of an energy transfer?

  Efficiency = useful energy ( or power)

  -----------------------

  total energy (or power)
• Name two ways to reduce unwanted energy transfer.

  Lubricant and insulation
• What is the Equation to calculate kinetic energy?

  $E=$$1/2mv$
• What is the equation to calculate gravitational potential energy?

  $E=$$mgh$
• What is the equation to calculate elastic potential energy?

  $E=$$1/2ke^2$
• What is the equation to calculate energy needed to increase temperature of material?

  $E=$$mc0$
• Define specific heat capacity.

  Energy required to increase the temperature of 1kg of a substance by 1 (degrees C)
• Define power.

  Energy per second.
• What is the equation for power?

  E=Pt
• what is thermal conductivity?

  Rate at which heat conducts (conductors - high thermal conductivity and insulators - low thermal conductivity).
• Give three factors that determine the rate of thermal energy transfer through a material.

  Thermal conductivity of material,

  temperature difference,

  thickness of material