THERMAL CONDUCTIVITY OF INSULATING POWDER Determines thermal conductivity of insulating powder by sphere in sphere method. A copper sphere in which a mica heater is fitted. the sphere is surrounded by another bigger sphere and between the two sphere,the test insulating powder is filled. Heat of the heater radically flows outwards in all directions through powder. temp. Across the powder are measured. by knowing input to the heater conductivity of powder can be dtermined. Qty :