Energy Changes and Transfers

Changes in Energy

• When something happens, energy changes or is transferred.
  • Example: Eating food (chemical energy) leads to running (kinetic energy), which can further change to gravitational potential energy when running to a higher ground.

Energy Storage and Change

• Before energy is changed or transferred, it is stored.
  • Example: Energy is stored in wood (chemical energy); burning transforms this into thermal energy.

Energy Transformation Examples

• Flowing water (kinetic energy): Used to spin a turbine (kinetic energy), which then powers a generator to produce electrical energy.

Forms of Energy

• Different forms of energy include:
  • Chemical
  • Thermal
  • Electrical
  • Sound
  • Light
  • Gravitational
  • Kinetic
• A process or event changes or transfers energy. These processes can be represented as arrow diagrams showing energy changes (e.g., Electrical → Heat, Electrical → Light).

Useful vs. Wasted Energy

• When energy is transferred or changed, some of it is useful, while some is wasted.
  • Example:
    • Electrical → Light: 15% useful (light), 85% wasted (thermal)
    • Electrical → Light: 50% useful, 50% wasted

Wasted Thermal Energy

• Every time energy changes or is transferred, some thermal energy is wasted (dissipated).
  • Example: Burning wood (chemical energy) to change to thermal energy also heats the rock and air around it.
  • Some chemical energy is also transferred to light and sound energy.
  • All of these are wasted and dissipated energy.
• Dissipated energy:
  • Spreads out and becomes less useful.
  • Cannot be recovered.