PHYSICS LAB MANUALS

Thermal Conductivity of a Poor Conductor – Lee’s Method

Table II : The details of the physical quantities to be measured.

S.No

Physical quantity

Independent /

Dependent

Measured

with

Measuring instrument’s

Minimum

Maximum

Least count

1

Temperature






2

Time






3

Mass






4

Voltage






5

Current






  1. Measure the mass of the lower metal disc before and after the experiment, and the diameter of the sample poor conductor at different places (at least 6 measurements) using Vernier calipers.
  2. Take proper precaution not to burn your hands.
  3. Assemble the Lee’s disc apparatus and measure the thickness of the sample in situ using a microscope or a Vernier calipers or a screw gauge (at least 6 measurements).
  4. Pass steam through the steam chamber.
  5. When the steady state is reached (temperatures \(\theta_1\) and \(\theta_2\) change by less than 0.5\(^\circ\) Celsius in 1 minute) and make a note of \(\theta_1\) and \(\theta_2\).
  6. To find the rate of heat loss from B, take away the sample D (Hold the steam chamber (C) using gloves and carefully remove the poor conductor disk using gloves) and heat B directly from C until its temperature has risen by about 10\(^\circ\)C.
  7. Then remove C using gloves and cover the top part of B again with the sample D.
  8. At intervals of a minute, measure the temperature of B and plot it as a function of time. Ensure that there are minimum 5 points above and below the \(\theta_1\).

Figure 1: heat flow equation

Figure 2: Measurements to be taken – Lee’s apparatus (here glass disc can be used as a bad conductor)
Table III: Measurement of temperature with respect to time.

Time (s)

Temperature (℃)

1



2 …



10 …



… till required temperature