Material Choice and Selection

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  • Material Choice & selection
    • Density of a material is the amount of matter (mass) in an object per unit of space occupied by the matter (volume)
      • Relative density is a ratio used to compare material densities to water
    • Electrical Conductivity is the movement of electricity through a piece of material
      • Gold, silver , copper , liquids and some gases are good conductors
      • insulating materials can resist the flow of electric current. e.g wood, ceramics , plastics
    • a physical property is any property or mass or energy that can be measured per unit mass of a material
    • Thermal conductivity is the movement of heat through a material
    • conduction involves transfer of energy within a material without any motion of the material as a whole. conduction rates vary according to a materials reaction to heat so it is important to choose the correct material for the teask.
    • summary , insulating materials have low conductivity. used to prevent heat gain or loss often used in products to protect users from heat.
    • air is a good insulator and is used with other, materials to prevent heat loss
      • Double glazed windows use a combination of air and glass to create a barrier to prevent heat loss
    • Polystyrene is pumped into cavities between exterior brick and interior block. the beads and air space between each bead keeps warm air inside and cold air outside.

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