Lee’s method Experiment Procedure, Observations & Calculations, Result, Viva 2023

Hello guys in this we learn about Lee’s method experiment. In this experiment cover this point what is the working principle of Lee’s method and Lee’s disc experiment calculation, Lee’s disc method for determining thermal, Lee’s experiment procedure, Lee’s method experiment Viva questions and principle of Lee’s disc method in general, the upper part of Lee’s disc apparatus.

Aim :

To determine the thermal conductivity of a bad conductor by Lees’ method.

Apparatus :

Thin slab of bad conducting material, two thermometers, stopwatch, vernier callipers, micrometre screw and balance.

Formula :

Diagram :

 

Procedure :

1. Weigh the lower disc and find out its mass (M).
2. Using the Vernier callipers, measure the diameter (D) of thin slab of bad conducting material at five different points.
3. Using micrometre screw, measure the thickness (x) of the thin slab of bad conducting material at ten different places.
4. Set up the apparatus as shown in figure, by placing the slab between the discs. Pass steam through the upper disc continuously. Insert the thermometers T1 and T2 in the holes bored in the upper and lower discs respectively.
5. The temperatures of lower and upper discs go on increasing. After sufficiently long time, they become constant (Steady state). 
6. Note down the steady state temperatures and of the upper and lower discs.
7. Remove the thermometer T1 and the slab. Heat the lower disc by keeping the upper disc in direct contact with the lower disc. Pass the steam through upper disc so that the temperature of the lower disc rises by about 100C above the steady state temperature. 
8. Now remove the upper disc and keep the slab on the lower disc. The temperature of the lower disc goes on decreasing due to radiation of heat from the lower surface and sides.
9. Note down the temperature (t) of the lower disc using the thermometer T2 at an interval of 30 seconds. Continue this until the temperature of the disc goes below the steady state temperature (t) by about 100C.
10. Plot a graph of against t. 11) Determine the slope at 5 different suitable values of θ. 
11. Plot a graph of slope (t) against θ and hence determine.

Observation :

1. What is Thermal Conductivity? 

Ans : The rate of heat conduction through a material of unit thickness and unit cross-section area for each Kelvin of temperature difference.

2. What are the units of Thermal Conductivity? 

Ans : SI unit is – Joule/second meter Kelvin.

3. Does the value of thermal conductivity depend on the dimension of the specimen? 

Ans : No, it depends on the material of the specimen.

4. Is there any reason to take the specimen in the form of a disc in Lee’s experiment? 

Ans : A thin disc is taken because it’s area of cross-section is large, while thickness is small. It increases the quantity of heat conducted across its faces.

5. What is the largest source of error in this experiment? 

Ans : The largest source of error lies in the measurement of rate of cooling.