11.6 Conductivity of Poor Conductors

In the case of poor conductors as the heat conduction is very small, the specimen can not be taken as bars as in the case of the good conductors because in that case the heat loss from the sides will be many times the heat conducted. Since the rate of flow of heat is proportional to the cross sectional area and inversely proportional to the thickness, substances in the form of a thin plate, sphere or cylinder will be favourable. Wood, rubber, glass, asbestos, clay and cork are poor conductors.

We shall consider here three methods of determining thermal conductivities; they are:

  1. Lee's disc method
  2. Spherical shell method
  3. Cylindrical shell method

11.6.1 Lees’ Disc Method

This method is used to measure thermal ...

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