Physics-energy and electricity

• Key Terms:

  • Energy: a property which must be transferred for something to happen (e.g. an object to move or heat up)
  • Useful energy: the intended energy type released by a device (e.g. the useful energy of a lamp is light energy)
  • Wasted energy: the unwanted energy released by a device (e.g. the wasted energy of a lamp is heat energy)
  • Efficiency: the proportion of useful energy released by a device compared to the total energy it uses
  • Power: how quickly energy is used up
  • Gravitational potential energy: energy stored in objects lifted above the ground
  • Kinetic energy: the energy of a moving object
• Energy types:

  • Chemical energy: found in fuel, food, and batteries
  • Elastic energy: found in compressed or stretched springy objects
  • Kinetic energy: found in moving objects
  • Gravitational potential energy: increases as an object is lifted above the ground
  • Electrical energy: transferred when electrons/electrical current flows
  • Thermal energy: released when objects emit heat
  • Nuclear energy: found in nuclear reactors and nuclear bombs
  • Sound energy: caused by vibrations in the air
  • Light energy: released by lamps, fires, stars
• Energy equations:

  • Energy = power x time
  • Power = energy/time
  • Time = energy/power
• Relationship between gravitational potential and kinetic energy:

  • The roller coaster has high gravitational (potential) energy at the top of the slope because it is high above the ground and low kinetic energy because it is moving slowly or not at all
  • As it gets closer to the ground and faster, gravitational energy decreases as it is being turned into kinetic energy which increases
• Relationship between charge, current, and time:

  • Charge = current x time
  • Current = charge/time
  • Time = current/charge
• Sankey diagrams for useful and wasted energy:

  • A Sankey diagram allows you to work out how efficient something is
  • In an example, a light bulb uses 7 out of 10 Joules of energy for its desired purpose - to release light, making its efficiency 70%