7.5 - Reducing Unwanted Energy Transfers

• What is the main focus of today's video?

  Reducing unwanted energy transfers
• What are the two methods discussed for reducing energy loss?

  Thermal insulation and lubrication
• Why is it important to understand the principles of energy loss reduction?

  To suggest solutions in exam questions
• What do most people prefer for their homes regarding temperature?

  Nice and warm
• What is the goal of reducing heat energy loss in homes?

  To prevent heat from escaping outside
• What is convection in the context of heat transfer?

  Heat transfer through liquids and gases
• How do foam seals around doors and windows help?

  They prevent air from passing out
• What is conduction in terms of heat loss?

  Heat lost directly through solids
• What type of walls do houses typically have to reduce heat loss?

  Thick walls with low thermal conductivity
• What are cavity walls?

  Two layers of bricks with an air gap
• Why is air a poor conductor of heat?

  Because it does not transfer heat well
• What is the purpose of insulating foam in cavity walls?

  To reduce convection and conduction
• What is the difference between single and double glazing?

  Single has one pane, double has two
• How does double glazing reduce heat loss?

  By having an air gap between glass layers
• What is friction in the context of energy transfer?

  Resistance when moving over a solid
• Why is reducing friction important?

  It increases the efficiency of energy transfer
• How does adding oil to bicycle parts help?

  It reduces friction for easier pedaling
• How does streamlining vehicles affect energy use?

  It reduces air resistance and fuel consumption
• What is the main benefit of reducing unwanted energy transfers?

  Improved efficiency in energy use
• What are the methods to reduce unwanted energy transfers in homes?

  • Thermal insulation
  • Lubrication
  • Sealing air leaks
  • Using cavity walls
  • Double glazing
• What are the effects of friction on energy transfer?

  • Reduces efficiency of energy transfer
  • Causes objects to heat up
  • Makes movement harder
• What are the characteristics of effective thermal insulation?

  • Low thermal conductivity
  • Thick materials
  • Air gaps or insulating foam
• How does double glazing work to reduce heat loss?

  • Two layers of glass
  • Tiny air gap between layers
  • Reduces conduction of heat
• What is the role of lubricants in reducing friction?

  • Decrease resistance in moving parts
  • Improve efficiency of machines
  • Prevent overheating
• Which type of heat loss do foam seals around windows and doors help to minimise?

  • Heat loss by convection
  • Foam seals reduce heat loss by convection because they reduce air flow in and out of the building. 
• What are some features of a house which help to reduce heat loss by conduction?

  • Walls made of a material with low thermal conductivity
  • Cavity walls
  • Double glazed windows
• What is the purpose of putting insulating foam in cavity walls?

  To minimise air convection currents
• Single glazed windows only have one pane of glass, whereas double glazed windows have two panes of glass. In both cases, the panes of glass reduce heat loss by convection.

  The added benefit of double glazing is that there is a small air gap between the two panes of glass, which minimises conduction (as air is a poor conductor of heat).
• What is being described by the following sentence?

  "The resistance that an object encounters when moving across a solid, or moving through a liquid"

  Friction
• Which of the following helps to reduce friction between two surfaces?

  Sand

  Rubber

  Lubricant

  Lubricant
• Fast moving vehicles like cars and planes have a streamlined shape to reduce friction from air resistance. This allows them to use less fuel.
• Why does cavity wall insulation contain pockets of trapped air?

  Air is a good insulator
• EXAMPLE: