1.1 Material Selection — Part 2: Physical properties

What are the three physical properties specifically required by the CCEA specification?

Density, electrical conductivity and thermal conductivity

What is density?

The amount of matter (mass) in an object per unit of space (volume) occupied by the matter.

What temperature of pure water is used when calculating relative density according to the CCEA fact file?

4°C

What is electrical conductivity?

The ability of a material to allow electricity/electric current to pass through it.

What is an electrical insulator?

A material that resists the flow of electric current.

What is thermal conductivity?

The ability of a material to allow heat to pass through it.

When does conduction occur in a solid material?

When a temperature gradient exists.

What is the relationship between thermal conductivity and insulation?

Materials with a high insulating value generally have low thermal conductivity.

Why is air a useful insulator?

Air has very good insulating properties and can be used with other materials to reduce heat loss.

What is thermal expansion?

The increase in the dimensions of a material as a result of heating.

Why must thermal expansion be considered when selecting a material?

Changes in temperature can cause a material to expand and contract, which may affect the dimensions, fit or performance of a product.