Lecture Notes: Energy Concepts

Introduction to Energy

• Energy is comparable to money and can be stored or transferred between different stores.
• Energy can be visualized like a liquid that is transferred between stores.

Types of Energy Stores

1. Kinetic Energy
   • Related to the speed of moving objects.
2. Elastic Potential Energy
   • Concerns deformation, like squashing or stretching objects.
3. Gravitational Potential Energy
   • Related to an object's height above ground.
4. Thermal Energy
   • Refers to internal energy.

Calculating Energy

• Kinetic Energy (KE):
  • Formula: ( KE = \frac{1}{2}mv^2 )
  • 'm' is mass in kilograms.
  • 'v' is velocity in meters per second.
• Elastic Potential Energy (EPE):
  • Formula: ( EPE = \frac{1}{2}ke^2 )
  • 'k' is spring stiffness in Newtons/meter.
  • 'e' is extension in meters.
• Gravitational Potential Energy (GPE):
  • Formula: ( GPE = mgh )
  • 'g' is gravitational field strength, typically 9.8 N/kg on Earth.
  • 'h' is height in meters.
• Thermal Energy Change:
  • Formula: ( \Delta E = mc\Delta\theta )
  • 'c' is specific heat capacity (J/kg°C).
  • 'Δθ' is temperature change in °C.

Energy Transfer Processes

1. Heating
2. Electrical Working
3. Radiation
   • Includes sound and light waves.
4. Mechanical

• Energy transfers from one store to another, e.g., kinetic to gravitational potential when an object is projected upwards.

Power

• Defined as the rate of energy transfer or work done.
• Formula: ( \text{Power} = \frac{\text{Energy transferred}}{\text{Time}} )
• Power is measured in watts.

Efficiency

• Efficiency measures how well energy is transferred to a useful store.
• Formula for efficiency:
  • ( \text{Efficiency} = \frac{\text{Useful output energy}}{\text{Total input energy}} )
• Efficiency can be expressed as a percentage.

Energy Resources

• Non-renewable Resources:

  • Include coal, oil, gas, and nuclear fuels.
  • Once used, cannot be replenished.

• Renewable Resources:

  • Include biofuels, wind turbines, solar cells, geothermal, hydro, wave, and tidal energy.
  • Tend to be more sustainable as they are replenished naturally.

• Electricity Generation:

  • Involves boiling water to turn turbines and generators or harnessing natural forces like wind and sunlight directly.

Conclusion

• Understanding energy, its stores, and transfers is crucial for solving problems and optimizing processes efficiently.