The accompanying sketch shows the schematic arrangement for measuring

the thermal conductivity by the guarded hot plate method. Two similar 1 cm

thick specimens receive heat from a 6.5 cm by 6.5 cm guard heater. When

the power dissipation by the wattmeter was 15 W, the thermocouples

inserted at the hot and cold surfaces indicated temperatures as 325 K and

300 K. What is the thermal conductivity of the test specimen material?​