Wasted Energy (AQA GCSE Physics)

• In practice, most systems tend to be open systems
• When energy transfers occur that are not useful, these are described as energy being dissipated to the surroundings 
  • Dissipated just means spread out
  • This is considered to be wasted energy

• Often these less useful energy transfers often involve heating, light and sound
• When energy is transferred to the thermal stores of the objects, the temperature of the objects increases
  • The particles that make up the objects vibrate more, hence the transfer pathway is by heating (of the particles)
• Visible light is electromagnetic radiation
  • Therefore, when light is produced, energy is transferred by radiation
• When sound is produced, the sound waves make the air particles vibrate as the wave carries energy away 
  • This increases the energy in the thermal store of the air, hence the transfer pathway is by heating (of the particles)

• Useful energy can be defined as:

The energy that is transferred from store to store and used for an intended purpose

• Wasted energy can be defined as:

The energy that is not useful for the intended purpose and is dissipated to the surroundings 

• Mechanical processes can become wasteful when they cause a rise in temperature
• These processes often involve friction
  • When friction acts, it has the effect of transferring energy from the kinetic store by heating to the objects and the surroundings
  • This energy cannot be used in a useful way, therefore it is called wasted energy
  • Energy that is transferred to the surrounding is said to be dissipated (spread out) to the surroundings

Lubrication

• Friction is a major cause of wasted energy in machines
• For example, the gears on a bike can become hot if the rider has been cycling for a long time
  • Energy is wasted as it is transferred from the kinetic energy store of the bike to the thermal energy store of the gears and the chain
  • This friction makes them become hot and transfers energy by heating to the thermal energy store of the surrounding air

• This wasted energy can be reduced if the amount of friction can be reduced
  • This can be achieved by lubricating the parts that rub together

Lubrication helps reduce friction in the parts of a cycle

Insulation

• In many situations, the energy transferred by heating is wanted. For example:
  • When heating a home
  • When boiling a kettle

• If this energy can be prevented from dissipating, then less energy will be needed to replace the wasted energy
  • This can be achieved by surrounding the appliance with insulation

• The effectiveness of insulation depends upon:
  • How well the insulation conducts heat
  • How thick the insulation is