Energy Stores and Transfers

• What can be considered a system in physics?

  An object or group of objects
• What happens when energy is transferred between stores?

  Energy is transferred
• How can energy storage change in a system?

  Energy can change the way it is stored
• When is energy transferred between stores?

  When work is done by a force or by a current flowing
• What is the principle of conservation of energy?

  Energy cannot be created or destroyed
• How can you calculate the amount of energy transferred to stores in changing systems?

  By using specific formulas related to energy transfer
• What happens to energy when it is transferred to non-useful stores?

  Some energy is said to be wasted
• What are the energy stores you need to know?

  • Kinetic
  • Thermal (or internal energy)
  • Chemical
  • Gravitational potential
  • Elastic potential
  • Electrostatic
  • Magnetic
  • Nuclear
• What type of energy store does anything moving have?

  Kinetic energy store
• What does the thermal energy store depend on?

  The temperature of the object
• What can release energy by a chemical reaction?

  Fuel, food, cells
• What type of energy store is associated with mass in a gravitational field?

  Gravitational potential energy store
• What type of energy store is related to stretched or compressed objects?

  Elastic potential energy store
• What type of energy store involves electric charges interacting?

  Electrostatic energy store
• What type of energy store is associated with magnets?

  Magnetic energy store
• What type of energy store is found in atomic nuclei?

  Nuclear energy store
• What is a closed system?

  A system where neither matter nor energy can enter or leave
• What happens to the total energy in a closed system?

  The net change in total energy is always zero
• How can energy be transferred between stores?

  In four main ways: mechanically, electrically, by heating, and by radiation
• What is an example of mechanical energy transfer?

  An object moving due to a force acting on it
• What is an example of electrical energy transfer?

  A charge moving through a potential difference
• What is an example of energy transfer by heating?

  Energy transferred from a hotter object to a colder object
• What is an example of energy transfer by radiation?

  Energy from the Sun reaching Earth by light
• How is energy transferred when boiling water in a kettle?

  Energy is transferred to the water's thermal energy store by heating
• How is energy transferred in a jack-in-the-box toy?

  Energy is transferred mechanically from the elastic potential energy store to the kinetic and gravitational potential energy stores
• What does "work done" mean in terms of energy transfer?

  Work done is another way of saying energy transferred
• What happens when a person throws a ball upwards?

  Energy is transferred from the chemical energy store of the person's arm to the kinetic energy store of the arm and the ball
• What happens when a ball is dropped from a height?

  Energy is transferred from the ball's gravitational potential energy store to its kinetic energy store
• What does the friction between a car's brakes and its wheels do?

  It causes an energy transfer from the wheels' kinetic energy stores to the thermal energy stores of the brakes and surroundings
• What happens in a collision between a car and a stationary object?

  Kinetic energy is transferred from the car's kinetic energy store to other energy stores, such as elastic potential and thermal energy stores
• What does dissipated energy mean?

  Energy that is spread out and lost, often to thermal energy stores
• What does the conservation of energy principle state?

  Energy can be transferred, stored, or dissipated, but can never be created or destroyed
• How can you calculate energy transferred when a system changes?

  By using the conservation of energy principle
• What happens when a car applies brakes and comes to a stop?

  The energy in the kinetic energy store is transferred to the thermal energy stores of the brakes
• What formula can be used to calculate energy in a kinetic energy store?

  Energy = $\frac{1}{2}mv^2$
• How can you find the energy in an object's thermal energy stores?

  Using the formula $mc\Delta\theta$
• What happens in a closed system when energy is transferred?

  The total energy remains the same as energy moves between stores
• What is an example of energy transfer when a hot spoon is placed in cold water?

  The spoon cools down while the water warms up
• What is the definition of a closed system?

  A system where no energy can enter or leave
• What are the eight different forms of energy store?

  Kinetic, thermal, chemical, gravitational potential, elastic potential, electrostatic, magnetic, nuclear